WINTER / SEVERE

Winter Stormcast Zone
 OHIO VALLEY & MID-ATLANTIC

Southern Mid-Atlantic snow totals 

5:00 PM EST 2/19/12 Areas from eastern Virginia to central Virginia to the central Appalachians, as well as southern West Virginia and portions of the Shenandoah Valley are expected to receive highest impacts from the snow event into this evening 


WARNINGS & ADVISORIES (link)
Winter Storm Warnings current snowfall, noted in pink on the NWS map, include areas from central Virginia into to the central Appalachians, as well as southern West Virginia. Winter Weather Advisories are shown elsewhere in purple and extend to the Shenandoah Valley in the Richmond metro area, the Virginia Tidewater and the Maryland Eastern Shore. 

AMOUNTS

• 4-8" west central Virginia, eastern Kentucky, southern West Virginia.
• 2-4" for central and eastern Virginia including metro Richmond
• 1-2" in lower southern Maryland (St. Mary's County) and to the lower Eastern Shore (Somerset and Wicomico Counties)
• Coating to 1" from the Washington suburbs east to Annapolis.
• Light snow in the Baltimore metro area south of I-70

"NO or LOW IMPACT" 

The risk of snowfall north of the I-66 corridor and into the I-95 Washington to Philadelphia corridor is limited, and these areas may even avoid receiving any snow from this system. 

TIMING For Virginia and the central Appalachians, precipitation will enter these regions from southwest to northeast from mid-Sunday morning through the mid afternoon hours. By daybreak Monday the back edge of the snow should be exiting areas close to the Chesapeake Bay. 

IMPACTS For areas near the Chesapeake Bay, precipitation should begin as a mix of rain and snow, with a changeover expected from west to east during the late afternoon hours. 

• We expect travel delays across much of Central Virginia the region late Sunday afternoon and evening. In these areas, including the Roanoake to Lynchburg areas, and in the Richmond metro area, snowfall may be moderate to heavy at times during the evening hours. 
• Winds will increase to around 15 mph with higher gusts by early evening, and combined with the heavy, wet consistency of the snow isolated power outages will be a concern.

(Forecasters Foot, Isaacs, Greg, Mike, Jason; Meterologist Berk, Advisor Forrest)

1:00 PM EST 2/18/12 According to latest analysis by Meteorologist Justin Berk in collaboration with our team, the storm looks stronger and farther east as noted on recent computer model runs, including the NAM (North American Mesocale) and to lesser extent, the GFS (Global Forecast System). Please see the imagery below for evidence of this statement, as posted on Justin's page.

This trend has continued since late last night and is remains present in the modeling today. The GFS has been the middle of the road model, so it remains a good reference here. Notice the following difference between the GFS model and current observations:

• The surface Low in south TX was measured at 1005mb, a little deeper than the forecast 1007mb. At this point in development, that is important.
• The moderate to heavy rainfall was extending east of Dallas to north central Louisiana. The GFS shows a 6 hours total of rain leading up to 8am, but that still looks too light.
• Our High pressure is weaker than the forecast 1020mb vs 1023mb over MD. This shows less resistance pushing against the storm from our region.

As we get closer to the onset of precipitation we will be monitoring the changes between the models and update you on the changes. 

"This system means business"
-Meteorologist Shundra Stewart, Central Mississippi

9:00 EST 2/18/12 | Meteorologist Shundra Stewart of our Foot's Forecast | Central Mississippi zone nailed this morning what many on our team have been thinking since last night. We will have additional updates as the morning progresses. 

We first wanted to show you why Shundra feels as strongly about the storm potential as us... A 3000-mile plume of tropical moisture from the East Pacific is hard to ignore. Forecaster Connor of our Central Maryland team noted that several computer models have begun the interesting shift back north in the eventual storm path Sunday into Monday. More details at our lead story.

Need another tidbit? Take a look this fun quote from the Winter Storm Watch statement from the Blacksburg VA National WeatherService. This should give pause to astute readers, meteorologists and scientists out there ... "

"A STORM SYSTEM WILL SLIDE JUST TO THE SOUTH OF THE REGION SATURDAY NIGHT AND SUNDAY...AND THEN TURN NORTHEAST UP THE MID-ATLANTIC COAST AND STRENGTHEN BY LATE SUNDAY INTO SUNDAY EVENING."

Things that make you go hmm... 

Forecasters Foot, Isaacs, Stewart, Connor, Advisors Palmer and Winstead

1:50 AM 2/18/12 Good Morning Mid-Atlantic readers! We are getting closer to the onset of potential wintry weather for the area. Computer models for the past several runs have been trending further south as we approach the beginning of the event. Despite these apparent trends, we have been watching several key developments that we believe will affect the storm path and snowfall potential in the Mid-Atlantic:

• A rapidly developing surface low pressure system in southern Texas has begun tapping a powerful feed of moisture from the equatorial East Pacific. 
• This additional moisture feed from an area of 85 degree ocean water may indicate a larger system will unfold than is currently modeled. 
• If the system continues to intensify it could lead to significant changes and impacts, including widespread severe weather in the Southeast, and heavy snow in parts of the central and southern Mid-Atlantic.

LATE NIGHT DEVELOPMENTS SUGGESTING CHANGES

• The National Hurricane Center issued this graphical marine forecast, possibly out of concern that the surface low pressure was significantly lower than originally modeled. 
• The Storm Prediction Center has just put out a Mesoscale Discussion noting the rapidly developing potential for significant severe weather in central Texas. Again this explosive development was not forecasted on recent model runs. 

TEAM STATEMENT ON STORM SCENARIOS

Scenario A (Southern Slider)

• The storm travels further south this would leave most of the Baltimore and Washington DC area with very little precipitation and areas to the south with more potential snowfall. 
• Cities further south could receive the potantial for 3 or more inches of snowfall, expecially in Central and South Central Virginia. If this track is correct cities further west could receive 5-8 inches in the Appalachian Mountain region. (Jason Isaacs)

Scenario B (Northern Nuisance)

• The storm travels further north, first bringing a rain/snow mix and ending as snow to the I-95 corridor and east. Portions west of I-95 in the southern Mid-Atlantic remains generally all snow. 
• Snowfall accumulations would range from 3-6 inches across western Virginia to Southern Maryland. There would be a tight gradient of snowfall accumulations north of DC, with 1-3 inches near the Mason Dixon line. (Jason Mitchell)

Scenario C (Wild Card) 

• Surprise Snow? This storm is demonstrating remarkable similarities in terms of positioning of the low-pressure center and the high-pressure centers, and expected storm track to a storm on January 30, 2010. 
• Both the storm we are watching now, and the storm in 2010 came in as a “Southern Slider”. However, in 2010, the polar vortex was positioned about 100 miles north of where it was modeled to be, which allowed the storm to move back northward. 
• If you take a look at our benchmarks earlier, the positioning of the high pressure near the Great Lakes will be key. This wild card potential may occur if a stronger than modeled low plows into a weaker than modeled high, allowing the storm to come back northward, as on January 30, 2010 (Mike Natoli)

Snow Scenarios

SCENARIO A: The storm travels further north than expected, first bringing rain on Saturday night into Sunday, ending as snow to the I-95 corridor and east. Areas west of I-95 in the southern Mid-Atlantic remains generally all snow.

SCENARIO B: A storm track just offshore would bring snowfall to the central Mid-Atlantic region. The highest impacts for snow would be along the I-95 corridor, especially in the big cities from Philadelphia to Washington, with significant amounts of heavy, wet snow on roadways.

Map by Forecaster Jason Warren of Northeast Ohio, Team Statement by Forecaster Jason M. of the Capital Region, and the Winter Stormcast Team.

Definite uncertainty

11:25 AM EST 2/17/12  Most recent runs of the Global Forecast System are projecting that the eventual surface low in the Southeast may be approximately 40 miles more north than was expected as of last nights runs. 

This image from Meteorologist Justin Berk posted earlier this morning for snowfall projections for Baltimore-Washington Airport shows the disparity between two forecast models from earlier this morning. This is behind our  rationale for why we will issue snowfall projections "inside 48 hours."

This could have the effect of holding the storm over land longer, and allowing the precipitation shield to move farther north than currently expected. Readers in the Appalachians, Blue Ridge Mountains, and even along the I-95 corridor are advised to closely monitor National Weather Service forecast offices for any watches or warnings which may be issued tonight.  

OVERVIEW OF STORM EVOLUTION

• Development: Computer models are showing the two jet streams across the country combining together Saturday to produce a deepening storm system ro move across the Southeast 
• Track: Low pressure is expected to track from the Southeast U.S. to the Mid Atlantic coast during the day Sunday.
• Timing: Computer models are now delaying the precipitation onset until early to mid Sunday morning, and exiting the region Sunday night.
• Precipitation: The storm should begin for most regions as rain from Virginia on south, with an area of snow to the north. Given that surface temperatures will be near to above freezing, rain may mix with snow for a period on Sunday, before changing to all snow. 

Forecast Analysis 
by our Meteorologist-Advisors

11:45 PM EST 2/16/12

Our Winter Stormcast Team continues to see the potential for a significant winter storm to strike the region late this President’s Day weekend.  Computer models are showing the two jet streams across the country combining together Saturday night to produce a deepening storm system for Sunday. Low pressure is expected to track from the Southeast U.S. to the Mid Atlantic coast during the day Sunday, with a swath of rain and snow expected. Computer models are now delaying the precipitation onset until early to mid Sunday morning. Precipitation should exit the region by late Sunday evening.  Our team has outlined two scenarios for this weekend storm.

SCENARIO A: The storm travels further north, first bringing rain ending as snow to the I-95 corridor and east. Portions west of I-95 in the southern Mid-Atlantic remains generally all snow .

SCENARIO B: A storm track just offshore would bring snowfall to the central Mid-Atlantic region. The highest impacts for snow would be along the I-95 corridor, especially in the big cities from Philadelphia to Washington, if this scenario unfolds. (Forecasters Jason M. Dakota S., and the Winter Stormcast Team)

8:00 PM EST 2/16/12 | Analysis by the Winter Stormcast Advisors: 

AMS Certified Broadcast Meteorologist Justin Berk (4:00 PM)

• This 2 PM output from the GFS shown above is not the only model. Keep in mind that it was the "worst" for accumulating snow potential yesterday, and now shows the "biggest threat", thus too early to fully trust.
• It is similar to the European (ECMWF), but that model has dropped a little farther south with the track. The Canadian (my rusted old friend) keeps the storm farther south now and snow south of Baltimore.
• If the map noted above from today's 2:00 PM model runs were to verify, it would bring moderate to significant snow- just west of Baltimore. BUT we have the same issue we have had all winter: The Chesapeake Bay is warmer than normal, which translates into mixing issues near I-95.
• The wind direction would be critical. I see (based on a compass) the wind north of 40 degrees (northeast to north) helping snow, but 50-90 degrees (Northeast to east)= mixing or more rain
• This map would be a lot of snow to northern Baltimore and Carroll Counties and west...but if the storm tracks south closer to Canadian model.. then those areas might be on the northern fringe, but better chance of snow for Baltimore City and I-95 region.

Research Meteorologist Dr. Pete Winstead (11:35 AM)

• Many of the generic 'ptype' indices favor snow for at least some of this event. Specifically, the track of the low is ideal; there is a weak high over southern Canada that should keep wind directions northerly (preventing much onshore warm low-level Atlantic air from getting in here);
• Atmospheric thickness profiles suggest much of the atmosphere will be below freezing, etc. however most of the model solutions (at this point) also keep near-surface temperatures above freezing here [in the I-95 corridor near the Chesapeake Bay for much of the event. 
• There just isn't much cold air for this system to work with and while there is a high in the right place to keep the flow from going easterly and bringing in warm air off the Atlantic - upstream temperatures are just not that cold. 
• So, we have to rely on "dynamical cooling" - the process by which a storm cools the atmosphere through upward vertical velocities. This can often be enough to overcome the lack of cold air. 

"Significant" now appears likely

5-day Precipitation Forecast as of 8 AM 2/16 shows 
0.50 to 1.0 inches of liquid over a wide swath of the I-40 to I-95 
Corridors from the Mid-South to the Mid-Atlantic.  

12:30 PM EST 2/16/12  Our latest analysis of projected liquid amounts from the Global Forecast System model for individual locations such as Washington DC suggest about an inch of liquid could fall, but the big question is how much of that liquid falls as rain and how much falls as frozen precipitation. 


Using Baltimore-Washington International Airport as a representative location, preliminary liquid equivalents are 0.52" of precip as snow, 0.59" of precip as rain and 0.16" as ice pellets. This is preliminary data and will change many more times until the event arrives, but gives you a sense of moisture amounts.


WHAT WE KNOW

• We can infer that half of the precipitation will fall as rain, and the other half will fall as snow, given current indications.
• Models have also suggested a trend to increase the low pressure intensity once it forms over the weekend as two pieces of energy align themselves with each other. 
• Precipitation is likely to be occuring from the Carolinas to the PA/MD line by Sunday morning, as either rain or snow.

WHAT WE'RE WATCHING

• If dynamic cooling were to become a factor, then additional cold air would tap into the system which would create a more snowier scenario. 
• With a high pressure apparently trying to establish to the north as shown on the main site image, it could be just enough to provide the cold air which the storm would need to increase the potential for more snowfall than many may currently be expecting.

10:30 AM EST 2/16/12 | In advance of mid-morning computer model analyses on what we have termed #PDIII, our Winter Stormcast Team would like to share the following overview of statements from various NOAA & National Weather Service resources. The section section details a climatological analysis of teleconnections we track ahead of major storms.

This information is being updated as information becomes available. Please continue refreshing the page every few minutes to get the latest details.

SECTION 1: NOAA STATEMENTS & RESOURCES

• NOAA Hydrometeorological Prediction Center (HPC) (2:31 AM) "...MODELS CONVERGING ON SIGNIFICANT WINTER STORM FOR MID ATLANTIC DAY 3...
• NOAA HPC Winter Weather Graphics: Day 3 Probability of 4"
• Precipitation Forecasts: 

SECTION 2: NWS FORECAST OFFICE DISCUSSIONS

• Sterling VA: (9:02 AM) "GUIDANCE HAS COME INTO BETTER AGREEMENT IN FORECASTING  CYCLONE TO INTERACT WITH NORTHERN STREAM SHORTWAVE TROUGH...CREATING A STRONGER LOW PRESSURE WITH A TRACK FARTHER NORTH...CLOSER TO CWA. UNCERTAINTY IS STILL HIGH IN WEEKEND FORECAST...BUT ACCUMULATING SNOW DOES APPEAR POSSIBLE."
• Wakefield VA (6:56 AM) "AT THIS TIME...IT STILL LOOKS AS IF THIS LO PRES SYSTEM MOVES TOO QUICKLY IN THE SRN STREAM AND OUT TO SEA TO ALLOW FOR ANY COLD AIR (LACK OF HI PRES TO THE N) TO BE IN PLACE FOR ANY POSSIBILITY OF SIGNIFICANT SNOW TO OCCUR." [IN THE WAKEFIELD VA FORECAST AREA]
• Philadelphia/Mount Holly (6:51 AM) "A FAIRLY SIGNIFICANT SHORT WAVE TROUGH [IS] TRACKING ACROSS TEXAS AND THE GULF COAST STATES. THIS TRACK WILL ALLOW PLENTY OF MOISTURE TO BE TRANSPORTED NORTHEASTWARD. SOME PRECIPITATION SHOULD BE PULLED ACROSS AT LEAST A PORTION OF THE [FORECAST AREA] THE ENSEMBLE MEMBERS SUGGEST DIFFERING SOLUTIONS, ALTHOUGH AT LEAST A TREND LOOKS TO BE POINTING TO A BIT MORE NORTHWARD DRIFT TO THE PRECIPITATION SHIELD."
• State College, PA (6:50 AM) "A DEVELOPING STORM SYSTEM OVER THE SOUTHEAST STATES WILL TRACK SOUTH OF PENNSYLVANIA ON SUNDAY....AT THIS POINT IT MAY BE PRUDENT TO START MENTIONING THE THREAT FOR MODERATE SNOW ACCUMULATION IN THE HAZARDOUS WEATHER OUTLOOK FOR AREAS SOUTH OF RT 22 AND I-81."

SECTION 3: CLIMATE TELECONNECTIONS

This section is our "Earth Systems analysis" of atmospheric and oceanic factors which influence the eventual storm track and also have a significant impact on storm dynamics at large scales.  

• North Atlantic Oscillation
• Arctic Oscillation
• Pacific-North American Index

Will history repeat?

NOAA Projection from the GFS for 8 AM Sunday 2/19
as of  8 PM Wednesday night. Wait until you see the latest!

8:00 AM EST 2/16/12 | Our confidence is increasing for a winter storm this President’s Weekend in the Mid-Atlantic. Recent computer model runs including the Canadian (or CMC) have shown a track which would bring snow over inland portions of the Mid-Atlantic, as well as to the coastal cities. A new update is in progress and will be posted by 9:00 AM on latest information.


THREE SCENARIOS: Outlined for the storm as of last night. If this storm pans out with either scenario B or C, we expect it to arrive in the region on Sunday. The image above for 8 AM EST Sunday is just one of many computer modeling programs we examine for long range clues and large scale influences.

There has been significant disparity among the major computer models, and the event is still 4 days away, which is why we cannot nail down one specific scenario this early. Additional details will be coming forward later this morning. 

Three scenarios are posted below in order of likelihood, (A highest, C lowest)

SCENARIO A – The storm is pushed well to the south of this region, and generally out to sea off the Carolina coast,. Impacts to the Mid-Atlantic would be limited to gusty winds and a few flurries. 

SCENARIO B – The storm cuts along the coast, then tracks slightly inland over New Jersey, first bringing heavy rain ending as snow to the I-95 corridor and east. If the storm takes this track, it would be able to drop potentially significant snowfall to the inland portions of the Mid-Atlantic, as far as Central Pennsylvania. 

SCENARIO C – This solution is a compromise of the previous two. A storm track just offshore would bring snowfall to the central Mid-Atlantic region. The highest impacts for snow would be along the I-95 corridor, especially in the big cities from Philadelphia to Washington, if this scenario unfolds. 

Is this "PD III?"

Meteorologist Justin Berk of Baltmore, MD posted this image in his public Facebook page earlier this week of the top 20 snowstorms in Baltimore. Take a close look at how many of those events occurred in and around what is known to some as President's Week. It's been 9 years since the last one...


Please stay tuned for more details and updates in the coming days! Also, stay tuned to your local forecast zone pages in Facebook or this site.

(Author: Forecaster Mike N. | Collaborators: Forecasters Greg J., Dakota S., Mitch D., Jason M., and Jason W.) 

"Chances are..."

8:15 PM 2/15/12 | With increasing potential for a winter weather event to affect a large part of the Mid-Atlantic late this weekend, the Winter Stormcast Team is holding a multi-state conference tonight at 9 PM EST. We plan to issue a statement before 11:00 PM.

With recent disparity in computer model projections for this event, the team will be harnessing data-heavy techniques that proved successful for our readers in the 2010 blizzards. 

Among the points to be made in a statement tonight: 

• Preliminary ideas on areas of highest impact;

• Discussion of liquid equivalents

• Three possible scenarios for President's Weekend

How much and when? If "significant snow" looks likely, our team begins posting snowfall ideas around the 72 hour mark. Given that we are more than 4 days away, that information is reserved until we have more clarity in the computer model data. Continue checking this page for the latest ideas. http://www.footsforecast.org/p/winter-stormcast_22.html

Mid-Atlantic: Changes and concerns
Update by Meteorologist Justin Berk

·      4:30 PM EST 2/15/12 | There have been a few adjustments with this morning's computer models. The European Model here still shows a significant storm for the Mid Atlantic Saturday night into Sunday. Meanwhile the GFS and Canadian models have gone in opposite directions and seem to have been initialized poorly- thus dismissed. Note that this is a 96 HOUR forecast. Tomorrow is when we start to focus on the specifics. See more here.

A Valentine's Tale of Two Storms
Forecaster Jason M. and the Winter Stormcast Team

6:45 PM EST 2/14/12 | A few computer models are indicating the potential for winter to make a strong comeback by late this weekend in the Mid-Atlantic. A rainstorm will affect the region Thursday, and behind this system models show a developing low pressure system along the Gulf Coast by Saturday.

• Option A: If this low takes a track out to sea, then the Mid-Atlantic will be left with dry conditions and seasonable temperatures through the holiday weekend. 
• Option B: If the system tracks along the Southeast and Mid-Atlantic coast, then we could be looking at snowy conditions for the region. 

As with nearly all winter storms, there is still plenty of uncertainty with this system. The best timing appears to be Sunday into early Monday, however that may change. You can count on our team to keep a close watch on this potential. Stay tuned to this page for more updates each day as the weekend approaches.    (Forecaster Jason M. and the Winter Stormcast Team)

Analysis of Weekend Storm Potential 
by Meteorologist Justin Berk and Advisor Rich Foot

9:00 AM EST 2/14/12 | EXAMINING PRESIDENT'S WEEKEND SNOW POTENTIAL Since we are inside 5 days from a possible winter weather event,in the East, our Winter Stormcast Team, in collaboration with Meteorologist Justin Berk, wanted to provide you with a heads up on what we are seeing on the horizon for Saturday and Sunday. Comments from Mr. Berk this morning on his public facebook page.

A model comparison 

Examine differences between the overnight European Model (ECMWF) to NOAA's Global Forecast System model (GFS) verifying at 8 AM EST Monday 2/20. It would seem there is a potential Sunday-Monday event... nor not? What a HUGE difference between a large storm east of Ocean City or clear sky with light wind! How can this happen?

• ECMWF: This model phases the northern and southern branch of the jet stream allowing the storm in the Gulf of Mexico to turn the corner up the coast. This location is a little east for a major hit in central MD, but it would produce snow and strong winds.
• GFS: This model does not allow the jet streams to join forces. As a result, High Pressure is allowed to arrive from Canada to protect Maryland and the Mid Atlantic region. This keeps the storm in the Gulf of Mexico with a much slower track. 

The pre-storm "look fors" 

Watching carefully how the atmosphere is behaving now and the physics of forces at play, especially how the Thursday storm in the Mid-Atlantic will behave. 

• If that area receives rain, but the system itself is stronger AND the new system off of the Pacific is stronger, then the jet stream will buckle more and the ECMWF will play out.

Tell us in the comments or on our Mid-Atlantic Winter Stormcast Page in Facebook what you would like to see happen? 

(Meteorologist Justin Berk, Forecaster Foot and the Winter Stormcast Team)

Mid-Atlantic Overview 

by Lead Forecaster Greg Jackson and the Winter Stormcast Team

PENNSYLVANIA: The hardest hit area in this storm will be southwestern portions including the city of Pittsburgh. Overnight, the snow picked up in intensity and will continue through most of the day on Saturday. 

• 3-6" Metro Pittsburgh region
• 1/2" to 1.5" Johnstown/South Central PA 
• Trace to 1" State College/Central PA 
• Coating to 1.5" Allentown/North East PA
• 1 - 3" Philadelphia/Southeast PA

All the precipitation should be out of the Central and Eastern portions of PA by afternoon. Stay tuned to our local zones for the latest, including forecasters in Three Rivers, Central Pennsylvania, Northeast PA and Southeast Pennsylvania

NORTHERN WEST VIRGINIA: Currently most of the area is experiencing light-moderate snow and should continue to see the steady snow through tomorrow evening. We expect accumulations in the mountains to be 6-12”. Elsewhere, west of the mountains will see accumulations of 2-4” by tomorrow evening. 

Follow the Potomac Ridge and Valley page for local reports.

MARYLAND: Light snow will continue on and off today, mixing with rain in southern counties, before changing back to all snow toward Saturday evening. 

• The counties N&W of I-95 in central MD will accumulate  1-2”. 
• Since areas along I-95 and south will not see a long period of snow we only expect a coating-1”. The precip should move out by 1am Sunday. 
• Stay tuned to The Capital Region, Central Maryland, The Bayshore of Maryland's Eastern Shore.

Forecaster Dakota, a meteorology student at Penn State, reporting on snow conditions there during today's winter weather event in the Mid-Atlantic.


I-70/I-95: Rush hour hassle

By Lead Forecasters Connor Meehan and Mike Natoli

6:30 AM 2/8/12 | Our next storm is just around the corner now, but like the trend has been this winter, this will not be a major event. 

TIMING & IMPACTS

Primary precipitation type to be snow. However, surface highs are expected in the upper 30's, which means that when snow starts to fall, much of the region will be above freezing.

• Most of the storm is expected to arrive in the region around 1 pm, with the heaviest precipitation occurring during our rush-hour commute home, between 5 and 7 pm. 
• Limited visibility, and after sunset, slick & snow covered roads. Most of the precipitation departing the Mid-Atlantic by 10 pm Wednesday evening.  

ACCUMULATIONS 

Most accumulations are expected on colder surfaces, like grass and cars, but again, some slick stickage to the roads is possible as well. 

• Some mixing with rain near and south of D.C./I-95 in southern MD 
• North of D.C.: 1-2 inches of slushy accumulation
• Near the PA/MD line: Isolated areas of up to 3" 
• East of I-95/south of BWI: Coating to an inch. Most accumulations are expected on colder surfaces, like grass and cars, but again, some slick stickage to the roads is possible as well. 

One example of how our Winter Stormcast Team provides local 

reports is provided by Lead Forecaster Greg Jackson 

from our Three Rivers Zone in Southwest Pennsylvania. 

NOAA / NWS WINTER RESOURCES & PRODUCTS | WINTER SAFETY
SNOW/ICE PROB.  | HEAVY SNOW DISCUSSION | PRECIP FORECASTS


Reports from our Winter Stormcasters 



Mid-Atlantic: Saturday snow scenarios
By Lead Forecasters Connor Meehan and Greg Jackson 

(Image: Simulated radar from the North American Mesoscale 
[NAM] for 8 PM EST Sunday evening 2/6, as of 8 AM Fri 2/3)

Updated 4:45 PM 2/3/12 | Happy Friday Mid-Atlantic! Who is wishing for some snow? Well your wishing may just be working to your advantage! Latest model trends have suggested our potential Superbowl Sunday storm may take a slightly more northern track, bringing a swath of light wintry precip through from extreme southern PA southward to central Virginia. 

The Winter Stormcast Team will hold a full collaboration this snow potential and post a statement late this evening. Until then, our synopsis is as follows:

1. High confidence this will be a nuisance snow event, impacting mainly grassy, untreated surfaces and accumulating on vehicles;

2. Duration will be fairly quick, from Saturday night to Sunday late morning as the highest probability of snowfall;

3. Amounts will be discussed in more detail in the team statement tonight.

Timing: The time frames are still being worked out, and will be much more ironed out later tonight, but here are our first thoughts on timing: Rain would begin across the region Saturday night, mixing with and changing to light snow from west to east by Sunday morning. If the snow does fully changes over in the early morning hours, there could be brief period of heavier snow before ending in the afternoon hours. If the storm does not slow down, or if cold air is not reinforced more than we expected presently, all precipitation should clear the region before nightfall on Superbowl Sunday.

Intensity: We are concerned this could "over-perform" due to enough cold air to possibly produce a few fairly heavy snow bands as mid- to late morning Sunday. The main issue for those traveling to gameday parties might be the unexpected hassle of clearing snow off untreated sidewalks and cars. We are concerned more about visibility than accumulations. We think a small window of 1-2 hrs of snow Sunday around noon could cause visibilities problems i in the pre-game rush to the store. We don't want Superbowl fans to get caught off guard and end their day with a fender-bender or worse.

Our Winter Stormcast team will be holding a team chat this evening, with a full team statement to follow on this and our local forecast pages.  

9:00 AM EST 2/3/12 | As you may have heard, there is the potential for a large portion of the Mid-Atlantic to see some snow this weekend as a low pressure system tracks to the south of the area. Even just 2 days prior to the possible event, there continues to be wide variety of solutions being shown by major computer models. The team has narrowed down this spread into two possible scenarios:

Scenario A - A low pressure system that brings blizzard conditions to the Mid-West moves towards the Mid-Atlantic but stays south, passing over the Carolinas, only bringing light rain to Virginia and southern Maryland. A few snow showers may wander into portions of south central Maryland, but the majority of the precipitation will be light and in the form of rain. 

At this time, this seems to be the more likely of the two scenarios. 

Scenario B - The same low pressure system that brings blizzard conditions to the Mid-West moves towards the Mid-Atlantic but takes a more northerly route bringing heavier precipitation into the colder portions of MD and southern PA. Marginal temperatures in southern Mid-Atlantic will result in more of a rain event with possible mixing of snow. 

This scenario, depending on the exact track, has the potential to bring the first significant snow fall to the Mid-Atlantic. Although this solution seems less likely at this time, it is still very much on the table. 

As more information becomes available and models come to a better consensus, we should have an updated post Friday night around this time. 

Written by: Lead Forecaster Connor (MD); Collaborators: Greg Jackson, Dakota Smith (PA), Ross Harris (NC), Jason Mitchell (MD) 

Northeast US : The battle for winter begins
By Forecast Advisor Mr. Foot, Baltimore MD

11:30 AM EST 1/31/12 | After a highly variable winter of storms that have been decidedly "out-of-season" the pattern may be shifting toward a more traditional cycle of cross-country events followed by Arctic outbreaks. Given that temperatures are heading into the 50 and 60s today for the East, we know many PowderhoundTM readers are beyond bewilderment as to how this winter can deliver at least one traditional Mid-Atlantic snowstorm. All we can say is, take heart friends, the battle for a Fabulous February is about to begin. 

Details on how this pattern change will play out in the next several days is available at this link to the lead story from 1/31/12.

Mid-Atlantic: Will it be a "Fabulous February" ?
By Lead Forecaster Jason Mitchell, Calvert County MD

5:00 PM 1/28/12 | Seasonal to above normal conditions have returned to the region, and abundant cold air does not appear likely for the Mid Atlantic for at least the remainder of this month. Thus, most precipitation that falls in the region until approximately February 5 should be in the form of rain.

Looking into the long range, there are no significant indications of cold and wintry conditions for the region until after February 5. Models and other signals suggest we will remain in a general wet regime with slightly above average temperatures possibly into the middle of February. The NOAA Climate Prediction Center's 6-10 day temperature outlook shows a majority of the U.S. in an above-normal temperature pattern until at least February 8.

As mentioned in previous outlooks, our team closely follows atmospheric teleconnections such as the North Atlantic Oscillation and Arctic Oscillation. These may help to drive the weather pattern for the region heading into the latter half of February. If these indicators flip towards a consistent negative state, then chances for significant wintry weather will increase over our region in the days that follow that change. (Forecaster Jason M. and the Winter Stormcast Team)

Mid-Atlantic: The January Thaw, and then...
By Lead Forecaster Jason Mitchell, Calvert County, MD

9:12 PM 1/20/12 | Although not likely to be crippling, a significant winter storm is still expected to impact much of the region. The most significant impacts are expected from the Baltimore metro area and into much of Pennsylvania. Surface high pressure stretching across the Northeast coast is funneling cold and dry conditions into the region, while warmer and more moist air overrides this airmass aloft. This will provide a favorable setup for a wintry mix tonight.

Precipitation should arrive around midnight from west to east, and will be in the form of snow for much of the region. Areas south of Baltimore will likely receive a snow and sleet mix. Temperatures for most areas west of the Chesapeake Bay and north of Washington, D.C. will remain below freezing overnight, and freezing rain will mix in. Temperatures north of a line from Charlottesville VA to Lexington Park MD will likely remain below freezing, and freezing rain will mix in for these areas. Areas farther to the south will likely changeover from snow/sleet directly to rain.
Most locations south of the Mason Dixon line will changeover to all rain by mid Saturday morning, with precipitation ending for all areas by mid afternoon. Stay tuned to your local FF forecast zone for details in your area. (Forecaster Jason M. Collaborators: Forecasters Greg J., Mike N., Josh O., Advisor Keith K.)
(current HPC surface weather map)

Western Great Lakes: New Alberta Clipper
 By Affiliate Forecaster Matt Baranowski in Chicago, IL

8:55 PM EST 12/29/11 | Alberta Clipper on the way | A classic Alberta Clipper is on its way to portions of the Northern United States and is set to lay down anywhere from a trace of snow to isolated 4 inch amounts near Lake Michigan. Visit our Affiliate website for the full report on this snow potential: http://www.stormcentral1st.com/ 

Alberta Clippers originate from portions of the Alberta Province in central Canada and dive southward into the Northern half of the United States. This weekend, another one is headed this way, and we will see more of these systems into January. Along with a snow potential, these quick movers also like to throw down a bit of cold air from Canada. This cooler air will be in place heading into Friday-Saturday but then will warm up in most locations heading into Sunday. These clipper type systems are weak in pressure and moisture so they usually deliver between 1-4 inches in most affected areas. (Graphic by Forecaster Matt B.)

Mid-Atlantic: A Blue Sky Christmas
by Regional Forecaster Mitch D. in Allentown, PA 

‎8:00 AM EST 12/23/11 | Some of you may have heard about the possibility of an east coast winter storm on Christmas. While a snowstorm seemed like a plausible solution a few days ago, it is an unlikely scenario now. There are two main reasons for this.

We are in an unfavorable pattern to receive snow. With the NAO (North Atlantic Oscillation) and AO (Arctic Oscillation) both being positive, it is very difficult for a system to take a classic winter storm track. The timing has to be perfect, and that does not look like it will happen this Christmas. Troughs simply cannot dig enough or slow down when there is nothing to block them from escaping quickly. As a result, the Christmas storm is likely to stay out at sea. 

A noticeable reduction in snowcover across the Eastern U.S. contributes to this problem.

http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow_usa.gif

Another reason is the lack of cold air. In most cases, we need a high pressure system to the north of the area to feed in cold air. For this storm, we have the opposite - a low pressure system, which will not allow any major cooling. When we do get a high to the north, it scurries by and goes into the Atlantic before a major cooldown can occur. The positive NAO is affecting this, also, as there is no blocking for the high to stay in place. Even if the storm did come closer to the coast, it would most likely be rain.

While people may want a white Christmas this year, the weather pattern does not support a miracle like the surprise storm last year. The way things are going now, we may have to wait till January to see any accumulating snow. 

(Forecaster Mitch D. and the Winter Stormcast Team)

The December 19-20, 2011 Blizzard
By Affiliate Forecaster ConvectiveWeather in Wylie, TX

The historic December 19, 2011 Blizzard that impacted much of the Southern Great Plains has departed, but in its wake, folks are still dealing with heavy snow and hazardous roadways. The big winners of this event were Northeast New Mexico, the Oklahoma Panhandle, Southeast Colorado, and Western Kansas. Snowfall in excess of 6 inches was widespread across this region.Some people across Oklahoma and Kansas saw amounts between 12 and 16 inches from this Winter Storm! Needless to say things were quite a mess last night and earlier today. Since then, many of the main highways and roadways have been made passable, but the more rural roadways are still treacherous. With Canadian air in place, much of this snow will remain on the ground for some time before melting off. Exercise caution if you are traveling across this region this week because more snow is on the way!

Another system will roll through the South Central US Thursday and Friday, bringing more snow to the region. In fact, areas farther to the south across West & North Texas could even see some flurries or light snow. At least minor accumulations are likely from the Panhandles and West Texas into Oklahoma; however, accumulations, if any, are less certain for areas farther south across North Texas, but not completely negligible. A lot will depend on the system – its track, tilt, and timing. A slower, stronger system would result in higher snowfall totals and more widespread coverage, whereas a weaker, faster system would only result in a glancing blow to a lucky few. If the first solution were to verify, as the latest Euro suggests, Dallas-Ft. Worth could even see some of the white stuff Friday or Saturday. -As always, I’ll keep you posted!

Christmas Week Storm: Central Plains 
 By Affiliate Forecaster Cirrus Weather in Hays, Kansas

10:40 PM CST 12/16/11 | Numerous computer models and public forecasts are pointing towards a major winter storm to impact portions of our region next week for Oklahoma, Kansas, and Nebraska. 

For this post, I'm going to be focusing on Kansas. Some of the models and other forecasts are showing the heavier snow generally in between the Arkansas River and the Oklahoma border in Southwest and south central Kansas. However I believe the outcome will be different this time.

Let's first do a refresher of how snowstorms so far this season have fared: 

• Southern Kansas first starts in the "bullseye" of heavy snow, and then at the last minute, BANG, the storm ends up going farther west and/or north than my forecasts and others predicted. I am think this may occur with the upcoming system. 

• I do believe Southwest Kansas, portions of South Central, Central, and Northeast Kansas may receive the heavier snow. However, this is a big "IF." With my luck, it may stay south just because Hays is not in the bullseye for once, but I'm willing to take a chance. 

NOAA Snow Probability Maps back up my projection, as shown in the attached link. Day 3 probability of at least 4" is noted at 70% for portions of southern Kansas:

Regarding accumulations, since the storm has not yet developed, but I do see increasing probability this system can produce significant snow in some areas. If current trends continue, 6" or more are possible by Tuesday.


For more information on this winter storm and more details on where the heaviest snow may fall, take a look at our official map for the storm released earlier this evening on the CirrusWx facebook page: 

Thank you all, have a nice evening, and stay warm!

Author: Cirrus Weather | Editor: Mr. Foot and the Winter Stormcast Team.

Heading Toward The Holidays

 By Affiliate Forecaster StormCentral in Metro Chicago 

9:00 AM CST 12/14/11 | What a mild pattern it certainty has been over the United States thus far this winter. Chicago, for example, is already on track to close the year with the second wettest December on record. Overall temperatures have been averaging 5-7 degrees above normal this first part of December. 

Heading into the holiday period of December 21-31, a more active storm pattern is expected to take effect, and details on this projected change are detailed in the following report for Foot's Forecast by the StormCentral Staff.

SYNOPSIS: By December 16,  a more active Pacific jet stream is set to take a large dip in the western United States and ride northeastward into the Ohio Valley. Were low pressure to develop, along with sustained cold air; locations from Wisconsin to Indiana could see a potential accumulating snow. This would be a dangerous storm track needing to be watched, as it points to Christmas weekend having the potential to be messy for travelers.  

ANALYSIS: In this new storm track scenario, some big snows would be possible for the Northeast, with widespread 6+ accumulations. The Western Great Lakes region may not be as affected by that storm, but any westerly movement has the potential to these  locations to be "side-swiped" by winter precipitation. Without negative readings from the NAO (North Atlantic Oscillation) or the AO (Arctic Oscillation) indices, sustained cold does not look likely for the rest of December. 

FORECAST: Overall, December looks to end on an active note with brief cool downs and an active storm pattern. Any storm system that develops and moves into the Ohio River Valley has the potential to swipe the Great Lakes region and could move into the Northeast. Most locations will likely end with December as "average" or slightly above in temperatures and above average in precipitation. Any storm that approaches a region this month may prove hard to forecast in precipitation type due to a variety of temperatures across many affected locations. (Affiliate Forecaster Matt B., StormCentral)

Matt is a sophomore at Maris Catholic High School in Southwest Chicago, Co-owner and Operator of StormCentral, Senior Patrol Leader of his Boy Scout troop and has led a lawn mowing/snow removal service in his neighbor in recent years. The U.S. Team of Foot's Forecast is pleased to announce this new Affiliation with the StormCentral staff. 

Mid-Atlantic Powderhound Report

10:10 PM EST 12/10/11 | By the Winter Stormcast Team

Despite varying chilly to mild weather over the region, there are no significant signs of snow for the Mid Atlantic through the next 5-10 days. The next storm system that may affect the region towards the end of next week appears to be a rainmaker for the region. Temperatures over the next couple weeks should generally be near to slightly below average. 

ANALYSIS: Snow cover over the northern U.S. and Canada should be much greater by the end of the year. The North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expected to be near neutral by the end of December. Recently, the NAO and AO have been moderately to strongly positive, which allowed for unseasonably warm air to be entrenched over the Mid Atlantic for the past few weeks. We believe these factors will help boost the chances of significant snow in this region over the next 2-3 weeks. 

FORECAST: We still anticipate the period of December 21-31 to feature the next chance for accumulating snow in the Mid Atlantic, with a much better chance by early January. (Forecasters Jason M., Greg J., Mitch D.; Advisor Mr. Foot)

About the Winter Stormcast Zone

12:00 PM EST 12/7/11 | By Lead Advisor Mr. Foot

We are excited to relaunch the popular winter weather forecast page which received millions of hits the past two winters. The Winter Stormcast Zone began in 2009, and by the February 2010 "Snowmageddon" readers poured into  by the hundreds of thousands for a straight scoop on what our winter forecasters were predicting. With the Northeast having already been clocked by the Shocktober Storm, and a storm bearing down on the Mid-Atlantic and Northeast, we are pleased to offer this headquarters of all our winter related forecasting.

WELCOMING OUR NEWEST PAGE TO THE WINTER FORECAST FAMILY: We have recently been joined by Forecaster Derek Maroot of Vermont, who now leads the Northern New England Winter Stormcast Page in Facebook. Derek is a professional pilot and in between his spare time, also leads the Northeast Kingdom Weather website for northern Vermont. If you are a New England Powderhound, or yearn to be on top of everything snow in that region, we invite you to visit and like Forecaster Derek's pages today.  

Winter 2011-12 Forecast Overview

INTRODUCTION After extensive collaboration over three months and across 5 states, the Winter Stormcast Team has prepared this overview of the Winter Forecast, We are also assembing a data-focused technical version that details the projected seasonal precipitation amounts for selected locations  similar to our "Storm Grade Amounts" approach. Part 2 is identifed as "Projections" to be released on or before December 1. This quantifiable method will establish specific amounts we project to occur, and then we can track the accuracy of that projection throughout the season as compared to climatology for that location. (Lead Forecasters Jason M., Connor M. and Lead Forecast Advisor Mr. Foot)

La Nina Projections for 2011-12

THE MAJOR PLAYER: La Nina. In a typical La Nina winter, the East Coast normally experiences below average snowfall and precipitation along with above average temperatures. The Climate Prediction Center currently expects a moderate La Nina this winter continuing into Spring, as stated in this recent report published 11/10/2011 and in the Weekly ENSO Diagnostic Report posted each Monday by the CPC.  

A La Nina Backgrounder on NOAA's page about the oceanic temperature phenomenon. 

INFLUENCING FACTORS: THE NAO & AO

We expect atmospheric teleconnections such as the North Atlantic Oscillation (NAO) and the Arctic Oscillation to be in phases that are conducive for below average temperatures at times this winter. This should mainly be the case for the first half of the winter. Thus, we expect below average temperatures with several chances for accumulating snow in December, with moderating temperatures later in the winter.

MID-ATLANTIC PRECIP & TEMPS

Overall for the Mid Atlantic, we expect slightly above average snowfall with near average precipitation and average temperatures. For northern portions of the Mid Atlantic, we expect the next significant snowfall event by December 5, with the remainder of the region receiving significant snow by the middle of December. 

A LOOK AT OTHER REGIONS

Areas in the Southeast U.S. should experience below average precipitation and above average temperatures. Our team is predicting below average temperatures and above average snowfall for the Pacific Northwest. Statements on the winter in different regions are in progress from our other Winter Stormcast Teams, and will be posted when complete.  

Prepared 11/7/2011, Updated 11/11/11

by the Mid-Atlantic Winter Stormcast Team. 

Lead Forecaster Jason M. 

Collaborating Forecasters: 

Connor M. (MD); Ross H. (NC); Mitch D. (PA); Mike N. (MD); Daniel R.(GA); Mark I. (WA)

LINKS TO RESOURCES:

1. North Atlantic Oscillation

Current status

(http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao_index_mrf.shtml )

2. La Nina/El Nino

(http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml )

The October 29-30, 2011 Snowstorm
By Forecaster Jason M. of Calvert Co., MD

7:25 PM 10/30/11 |  OCTOBER SNOWSTORM REVIEW | Lead Forecaster Jason Mitchell.

The historic winter-like storm that brought unprecedented October snowfall amounts to the Northeast will be remembered by many for decades to come.  NOAA ranked the event on the Northeast Snowfall Impact Scale (NESIS) as having a Category 1 level impact as compared to a "Category 5-level" impact for the March 1993 Superstorm. 


STORM GRADE VERIFICATION: A preliminary review of our Storm Grade Amounts as as verified by NWS Local Storm reports shows a 60% average accuracy for the 6 selected major cities in our forecast. Many thanks to Storm Chaser/Forecaster Kelton Halbert of TempestChasing.com in Nashville, Tennessee for conducting the independent verification of our forecast results. Kelton, a high school junior, was selected for this role because he was outside the forecast area of the storm and not involved in the prediction process. Additional storm data is available upon request via: footsforecast AT gmail.com
  

Several key factors were in place that contributed to this historic event. Following a strong cold frontal passage on Thursday, an anomalously cold area of high pressure set up over New England and southern Quebec. This allowed for early winter-like temperatures to descend over the Mid Atlantic and Northeast. 

DEVELOPMENT: A storm system began to develop Friday over the Tennessee Valley. A strong area of high pressure was also anchored over Greenland, and this “Greenland Block” helped to keep the storm on a southerly track through the Southeast. By early Saturday, the storm system reemerged off the Carolina coast. With favorable upper level dynamics in place, the storm rapidly intensified off the Mid Atlantic coast by the early afternoon hours. 

EVOLUTION: The high pressure to the north of the storm kept cold air in place over inland areas, and precipitation over portions of the Northeast quickly changed from rain to snow. The coastal storm continued to bomb (rapidly deepen over a 24 hour period) during the evening hours, and this allowed tremendous snowfall rates to persist over portions of New Jersey and Connecticut. 

IMPACTS: Temperatures in the lower to middle 30s allowed for low snow-to-liquid ratios, and the snow was very heavy. As a result of the heavy snowfall consistency, considerable tree damage occurred in many areas, and millions of people were without power. 

COMPUTER MODELS: As with nearly all nor’easters, there was plenty of computer model disagreement in advance of the storm. However, our review of model verification showed that the European Center for Medium-Range Weather Forecasting (ECMWF) model consistently projected this major coastal storm for several days. (Forecaster Jason M.)

"Shocktober" Snowstorm 

Latest team analysis

11:30 PM EDT 10/28/11 | STORM SYNOPSIS | Reposted from the Mid-Atlantic Winter Stormcast Zone in facebook by Forecaster Jason and the WSC Team: We are just hours away from a potentially record-breaking October snowstorm for interior portions of the Mid Atlantic. Although the main focus is on snow, wind and coastal flooding will also be hazards for other portions of the region. As the coastal storm deepens in classic fashion, winds will increase throughout the day over the Mid Atlantic. 

For the Atlantic beaches in Maryland, Delaware, and New Jersey, there will likely be a several hour period with sustained winds of 25-35 mph and gusts to 45 mph. Areas near the Chesapeake Bay should experience winds of 15-25 mph with gusts of 30-35 mph. 

Fortunately, winds will be a bit weaker in areas that will receive heavy snow. However, 10-20 mp may still be enough to help knock down leaf-covered tree limbs that are snow covered. Our Storm Grade Amounts for selected cities are listed below, many thanks to Forecasters Jason and Dakota for organizing the data for this chart. 

(Author: Forecaster Jason M. Collaborators: Forecasters Dakota S., Connor M., Mitchell D., Advisors Foot, Krichinsky)

BACKGROUND ON THIS PAGE

What started as a simple experiment that received just 200 hits a day in December 2009 grew by exponential rate to February 24, 2010 when nearly 150,000 individuals visited the Winter Stormcast Zone. By the winter of 2010-11, this page had become the go-to source for thousands on winter storm events. The Christmas Weekend Blizzard of 2010, the Southeast Ice Storm of January 8-10 and the January 26, 2011 "snow monsoon"  in the Mid-Atlantic among other events further cemented our "Winter Stormcast Team" as a reliable source for winter weather forecasting.