Thursday, March 5, 2015

Snow on schedule

Snow On Schedule

8:00 AM 3/5 - RADAR UPDATE (Forecaster Mike and the Winter Stormcast Team)

With moderate snow now being reported across the central Mid-Atlantic, the latest in a long series of significant winter storms is on schedule. Let us know you conditions - temperature, precipitation type, and if snowfall is sticking! For the next several hours to at least noon, areas seeing snow should expect up to 1" an hour with low visibility. 

ACCUMULATIONS - We still expect a region wide 5-8" of snow before all is said and done, with 3-6" south of route 50. Those southern areas actually have the best chance to get more than forecast of 3-6", if heavy banding occurs during the early afternoon. This is something we will be keeping a close eye on! See below for our final snowfall forecast map, and let us know how this event verifies in your area compared to the forecast.

ON TRACK? - The second wave of precipitation has arrived on schedule and precipitation rates will start to increase again. Similarly, the freezing line is progressing right on schedule. This storm trended a little later in its timing, but don't let the late start fool you into thinking it's nothing.
  • THIS MORNING - Snow, heavy at times, will continue across the region. Due to last night's rain and warm temperatures, it may have trouble sticking initially closest to the Bay (which is why we need your reports!). However, temperatures will continue dropping, reaching around 30º by noon with upper 20s NW and continuing to fall.
  • THIS AFTERNOON - Snow will continue, with the heaviest snow bands dumping just a little further south than this morning. Things will slowly track further south and east before tapering off between 4PM and 7PM.
  • TONIGHT - The system moves out and it's right back into the deep freeze. Expect lows in the upper single digits to lower teens across the region (ugh).

WILL SPRING COME, EVER? - While Friday will feel like the middle of winter, we will gradually moderate. We may even see temperatures near average for this time of year by the middle of next week! (Kinda sad when that feels like summer, huh?). After that, it's a little unclear if we stay warm or retrograde back, but from now on, the cold outbreaks will get weaker and weaker. Stay tuned and stay safe today!
(Forecaster Mike)

Wednesday, March 4, 2015

Winter Strikes Back

Winter Strikes Back


TIMING – Rain will move in with higher intensity this evening. start to mix with sleet for the NW counties around 10 PM-1 AM, then transition to all snow around 1 AM-4 AM. 
  • The metros will mix with sleet from 1AM-4AM and transition to all snow by 4AM-7AM with heavy snow possible across the region by daybreak. 

ACCUMULATIONS – We expect light sleet accumulations overnight, then around 5-8” of snow north of route 50. South of there, expect lesser totals. Roads will be hazardous across much of the Baltimore/DC Metro early Thursday morning, continuing through the day as temperatures drop. 

TEMPERATURES – Hovering in the lower 30s while we transition tonight, getting into the upper 20s early Thursday, mid 20s by midday, then rapidly plummeting to the lower teens overnight. 

BUST SCENARIOS – As with any forecast, there is a significant amount of uncertainty with this system. The last two years, we’ve had snow events in early March that did not live up to expectations. This system actually bears a lot of similarity to March 3rd, 2014. 

  • BAILING TO A BACHATA (20%) – The prime bust scenario would be a slow change-over to sleet and snow overnight would mean more water on the ground, warmer ground temperatures, and less snow. The cold will still come, but just a few hours later than what we expect could allow us to escape the worst of the impacts from this one. Less time in the snow means less snow falls, and less snow sticks, and most regions would fall more in the 3-5” range, struggling to get to the lower end. 
  • GOING "BIG KAHUNA" (20%) – Conversely, if we have a fast change-over to snow, and limited sleet, then much of the region is all snow well before daybreak. This allows for a burst of accumulating snow to whiten the ground again before sunrise, with ample moisture falling all as snow. This scenario could cause some people to receive over our 8” high end, with 8-10” common across the region.

  • Latest computer models including the European, GFS, NAM and others beginning to indicate a longer duration of snowfall on Thursday than first anticipated. Original ideas south of I-76 in PA to southern Maryland was snow ending by early afternoon then clearing.
  • New scenario being considered: (from central VA to southeastern PA) - a changeover of sleet/snow  to all snow by 5 AM, with all heavy snow from 6 AM to 12 PM, then light to moderate snow remainder of the afternoon, tapering after 4 PM. See Columbia, MD NWS hourly weather grid for timing in a representative location
  • This setup would significantly impact the AM and PM commute, whereas earlier ideas had more of just an AM impact with some inprovement toward the PM commute.


  • Heavy rain mixes with sleet late Wednesday evening and transition to snow from NW to SE starting around 10pm and reaching the Bay by 3AM. 
  • Then, several hours of heavy, accumulating snow until Thursday morning with temperatures dropping into the 20s. 
  • By the early afternoon, this scenario would bring a significant (4+”) snowfall region-wide. Some areas could see up to 10” of snow north and west of the 95 corridor.
  • This scenario would occur if the front stalls further north and cold air has a harder time moving in. Rain would continue falling through the evening mixing with sleet late at night. 
  • Then the transition to snow would occur Thursday morning from 3AM to 8AM. Snowfall would still be disruptive to the morning commute, but not quite to the high totals expected in Scenario A. 
  • Most places could still get up to a few inches for the metros, and maybe reaching the “significant” criteria north and west of the cities.
(Note: A revised timeline to be posted around Noon today)


4:00 PM 3/3 - OVERVIEW OF HAZARD TIMING & BASIC IMPACTS for the next 3 days for the Ohio Valley, Mid-Atlantic and Delmarva Regions. 
  • OVERNIGHT: Sleet and freezing rain this evening for areas south of I-76 transition to all rain by evening and continue into the daybreak hours as temperatures rise above 32 F by  midnight. 
  • WEDNESDAY: Moderate to heavy rain with temperatures in the 40s will lead to widespread snowmelt, runoff and some creek, low-lying and basement flooding.
  • WED NIGHT INTO THU: Rain begins mixing with sleet and snow in the evening, changing to heavy snow after midnight. Periods of heavy snow and snow-covered roads likely for the Thu AM commute. Daytime Thu temps in 20s drop to low teens overnight.

Tuesday, March 3, 2015

Meanwhile on Hoth

Meanwhile on Hoth

8:30 AM 3/2 - If you have been feeling like the region is beginning to resembles a Star Wars movie set, we would tend to agree. March is now the fifth straight month of wintry weather to be observed in the Mid-Atlantic. Appreciable snowfall for this season first began in mid November 2014 and show no signs of stopping.

IMPORTANT PLANNING MESSAGE FOR THE EDUCATIONAL COMMUNITY: We recognize that in some states such as Maryland, standardized testing is scheduled to commence this week and next across the state. With this in mind, we wish to provide the best available information about the weather pattern to aid school administrators in navigating this complex scheduling challenge ahead. 

This synopsis is valid for areas from I-76 in Pennsylvania south to the I-66 and I-50 corridors, including the Philadelphia, Baltimore and Washington DC metro areas. 

  • MON 3/2 - Dense ice on a several inches of snowpack will begin to fracture and melt with rising sun angle. This will lead to significant runoff into the evening. Temperatures are expected to drop below 20 F for most areas of the northern and central Mid-Atlantic north of the DC metro. 
  • TUE 3/3 - Runoff will have refrozen overnight and is likely to prompt more school delays due to widespread ice in parking lots, sidewalks and sidestreets. Residual moisture ahead of a warm front will reintroduce sleet and freezing rain toward the Tuesday PM commute. See the NOAA precipitation projection below for 7 PM Tuesday night.
  • WED 3/4 - Temperatures warming to the 50s will lead the most improvements in melting of snow and ice on sidewalks, driveways and snowpack. Extensive moisture ahead of a cold front will deliver up to 0.75" of rain across the Mid-Atlantic. However, the front will be fast-moving, and turn rain over to snow Wednesday night. 

  • THU 3/6 - Cold air rushing in behind the Wednesday frontal passage may change rain to snow by evening, continuing into Thursday AM. Warmer surfaces should negate some of the snowfall, so if forecasts are for 2-4" (as an example), warming and March sun angle may reduce actual accumulation to less than that. However, road conditions may be problematic again by daybreak Thursday. 
  • FRI 3/7 - Temperatures drop back to below freezing in wake of the Thursday front.  Any surface moisture, standing water or snowpack will refreeze Friday morning as highs are not expected to break 30 F for most areas.
We will continue to monitor the mid- and late-week developments and update later today when we have new information. 

If you liked our Star Wars Hoth reference, we defer the credit for the photo to this creative blogger which has a series of crafty and chuckle-worthy shots at Given the long and toilsome winter, it's our way of trying to use some humor to help warm hearts.

Mr. Foot, Forecaster Mike, Advisor Keith and the Winter Stormcast Team 

Sunday, March 1, 2015

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Saturday, February 28, 2015

Roaring into March

Roaring Into March

6:30 PM 2/28 - For the winter weary out there, although this next system is not exactly a "storm," it is going to speak volumes about why wintry weather requires adjusting to changing conditions. Failing to do so results in avoidable consequences, the risks of which were widely advertised well in advance.

Although the current NWS advisory map shows "only" Winter Weather Advisories for most of the Mid-Atlantic, we can sum up in two words what we believe conditions will closely resemble: LAST SATURDAY. 

Thus, our forecast and urging to be prepared on Sunday seems a virtual repeat of occurred throughout the region on Saturday 2/21:
  • Cold surface air in the teens and low 20s Sunday morning will allow for moisture overrunning at upper levels to fall as snow for the first 5-6 hours. The snow will stick on contact and create slippery road conditions within an hour.
  • Snow intensity will increase as the day progresses, and more travelers on the roads will confound the situation and hampering road crew efforts to address the snow.
  • Areas where less extensive pre-treatment of roads than otherwise might be expected for a weekday could lead to rapidly deteriorating conditions under 1-3" of snow followed by sleet and freezing rain.
  • The current precipitation and surface map projection for 7 AM Sunday indicates a widespread snow and ice situation affecting much of the Midwest, Ohio Valley and Mid-Atlantic states. 

By 1 PM Sunday, the widespread ice and snow is expected in these regions, continuing into the evening hours.

We hope that travelers and those holding Sunday service will make prudent and well-informed decisions whether adjustment to changing conditions is a more prudent action than "staying the course" if "ground truth" clearly presents a hazardous environment to the region by daybreak. Twice this winter, Sunday had an unpleasant outcome for many. We would prefer not to make it three.

Mr. Foot, Forecaster Mike Natoli and the Winter Stormcast Team

The hits keep coming

"And the hits just keep on comin'..."
- 1972 Album by the Monkees singer Michael Nesmith

Image source: NOAA Precipitation Projections for 7 PM Sunday 3/1

9:10 AM 2/28 - Updated team statement in progress. Synopsis of forecast concerns:
  • Significant cold surfaces in the Mid-Atlantic will be retained into Sunday as moisture overruns at upper levels. Precipitation will begin Sunday afternoon as mostly snow north of I-66, with sleet and freezing rain DC metro east. 
  • By evening, most precip will turn to freezing rain as upper and near surface temperatures warm to near 32 F -- continuing overnight into the Monday morning commute.
  • We disagree with the low-hazard assessment of this event as currently portrayed by the Sterling VA NWS as of 9:15 AM 2/28. The lack of a posted Hazardous Weather Outlook conveys a false sense of security to the public that a slight amount of freezing rain would not pose a measureable risk of hazardous travel. 
  • The 0.005" of freezing rain which occurred on Sunday morning, January 21 is evidence enough that the next 24-36 hours present an increasing risk of impactful weather to the Mid-Atlantic, as is currently depicted by the NOAA Weather Prediction Center.

Thursday, February 26, 2015

Southern Snow Surprise


Southern Snow Surprise...

  • Snow will fall rapidly and accumulate quickly due to cold surfaces. Up to 1" an hour is possible between 6 and 8 AM from the I-66 corridor to the I-95 corridor, including northern and central Maryland. Accumulation is expected to reach southern PA counties.

1:10 PM EST 2/25 - The climbing and expanding NWS Warnings, Watches and Advisories associated with the southern winter storm has no doubt set many to wondering about this system:
  • How much farther north might this storm track go?
  • Is there any potential for this system or "over or under" perform, and leave (or take away) a bigger surprise than current;y expected? 
We will address these two issues in the team statement below. We are not expecting a major snowstorm for the central and northern Mid-Atlantic, as most of the action should stay "south of DC" and centered on the Richmond metro area to the eastern shore. However, the problematic timing of this next potential event presents concern for the AM commute.

SYNOPSIS - The widespread winter storm which has been impacting the Deep South with extensive snow and ice will generally be kept to the south of the central Maryland region. 
  • However, we won't avoid seeing some snow from it. Tonight, Lows in the Mid-Atlantic will fall to the mid 20s overnight with increasing clouds ahead of the storm system passing by late. 
  • Precipitation on the northern edge of the system may bring light accumulations early Thursday morning. Though the Baltimore metro region will be on the periphery of the significant snow, it is worth mentioning as this system could cause some travel problems in the AM hours. 
  • A general rule with this event: The further south your location in the region, the more likely you are to see accumulating snow.
TIMING - Light snow in the metro area is expected by 3 AM Thursday, ending by 10 AM Thursday. 

ACCUMULATIONS - South of DC/Baltimore, we expect 1-2" of snow, with higher amounts near and east of the DC metro region. For Northern MD counties that border PA, snowfall will be lighter the farther your location is from the system. A dusting (or "Coating" up to 1" is possible.) 

HAZARDS - The timing (of course) during the AM rush will make for some difficult travel, especially south of the metros. Use caution on the roads if snow is falling, and give yourself a little extra time to get to work. Those north will have it a little easier, but if the storm trends just a little bit north, that could change. 

BUST POTENTIALS - What can go wrong with this storm? Unlike the last storm, the temperatures don't really matter much with this one. It's all about the track of the storm and extent of the precipitation field. 

  • THE BIG KAHUNA (20%): The computer model guidance has been trending significantly further north with each run lately. If this continues and the storm ends up even further north of where we expect, central MD isn't just on the fringes anymore. The excess moisture easily overcomes the dry air in place. This scenario could bring easily a significant snow south of the metros and accumulating snow to the north. Travel would be heavily impacted Thursday morning in this scenario. 

  • THE BUMMED BACHATA (15%): On the other hand, if the northerly trend in guidance abruptly reverses and the storm ends up south of expectations, northern MD ends up receiving no snow, while just a dusting reaching those south of the metros. This scenario would occur with a more southerly track of the low, or if the northern extent of the precipitation field doesn't reach as far as we expect. 

The situation with this storm could rapidly change (because it has been already), so stay with us for updates! We will keep you informed of the latest information.

(Map and Statement by Foreacaster Mike, Analysis and Forecasts by the Winter Stormcast Team

Monday, February 23, 2015

Please stop

Message to Old Man Winter: Please STOP.

10:45 AM EST 2/23 - As the Ohio Valley and Mid-Atlantic shovel the remaining slop that became of Saturday's over-performing snowfall, eyes and minds are looking for how the winter pattern reaches conclusion. The one glimmer of hope we see in the distant long range is a potential for above normal temperatures toward the middle of March. However the next 2-3 weeks may make you feel like winter has decided to start over from the beginning. The updated overview of our concerns going forward:

  • MELTING AND REFREEZING SNOWPACK in the East as temperatures dropping to the teens tonight in metro areas and possibly single digits in northern/western and rural areas, with sub-zero readings in the Appalachians.
  • SERIES OF LARGE ARCTIC HIGHS will ontinue the wave train of bitter cold air over the next 5-7 days, first entering the northern Plains then drifting toward the Ohio Valley and Mid-Atlantic. This will keep temperatures below normal for most of the week.
  • REACTIVATED SOUTHERN JET STREAM moving toward a more Spring-like pattern. It doesn't take an advanced meteorology degree to see how the convergence of this with large Arctic highs points to a primary hazard into early March: Multiple winter weather events. 
  • COASTAL MISCHIEF PLAYING AROUND on the medium range model maps, as evidenced by this westward creeping edge of precipitation from a coastal Low at the edge of the High. Image below is the Day 1-3 NOAA Liquid Potential through 7 AM Thursday.

THE PATTERN PLAN? SUCCESSIVE PERIODS OF WINTRY WEATHER may impact large areas late this week into early next week, starting in the Southwest - to the Deep South - to the Appalachians, then the Mid-Atlantic and Northeast. One glance at the 6-10 day outlooks from the Climate Prediction Center is evidence enough the wild winter ride is not stopping anytime soon.

Saturday, February 21, 2015

White and Wintry Weekend

 White* & Wintry Weekend

11:10 PM 2/21 - (Forecaster Mike from the Central Maryland Team) If you don't need to go out on the roads this evening, DON'T DRIVE! The roads are very bad and getting worse. If you can, stay off to give the road crews room to work. Temperatures are colder than modeled, but the change over to sleet and freezing rain is occurring as expected. This will actually only make the roads worse. 
  • What precipitation type are you seeing now? In College Park, MD I am observing freezing rain with a temperature of 28º. That is very very cold for freezing rain. 
  • OVERNIGHT - Mixed precipitation will slowly move north over the next few hours, and eventually switch to some plain rain around 10 PM-1 AM from south to north, but most of the precip will be out at that point. 
  • SUNDAY - Expected to be above freezing, so road conditions should gradually improve very late tonight and through the day. Stay safe out there!
6:10 PM 2/21 - SLEET ON THE WAY - OR NOT? Track the latest precip changes in this close up radar of the region from Intellicast. The real question is-- should you clear now or wait? 
  • If you clear the car now- the sleet and freezing rain collect ON your car, instead of on top of the snow. Our thought is to wait until it's all done, clear your walks first. Then clear cars last. Why? Because letting the sleet and ice collect on top of the snow, which absorbs and melts it, allowing the snowpack to get clumpy and then you can push it off in big chunks.
  • What are your approaches to clearing your car, walks or driveway in a "multi-precipitation event?"  We always welcome new perspectives on winter weather management.

2:20 PM 2/21 - IS THE BIG KAHUNA BACK? Heavy bands of snow are now moving through the DC/Baltimore metro areas for the next 2-3 hours, which will feature the highest snowfall rates of the entire event. If you haven't seen the "bucket dump" yet, get ready-- it's coming!
  • Our forecasters reported seeing sleet in local obs from northern and central Virginia, which indicates warmer air is working over the mountains. 
  • Any "changeover" to sleet may be preceded by very large, rapidly falling snowflakes, suggesting a slug of high moisture content has worked into the mid-levels. 
  • Track the lulls and bands in this useful, multi-feature radar from the College of DuPage for Sterling VA (scroll to right side of image for a US radar site map pullout)
SNOW TOTALS RISING? Short range models also print out up to 0.50" of liquid is still in the pipeline for areas currently receiving snow. That means another 2-4" is possible, and could easily bring all totals at least 2" above our earlier forecasts of 3-5" for I-95 south and east (to 5-7") and for N & W areas, what was 5-8" may end up as 7-9" or even 10". The potential for this was first outlined Friday afternoon in our Bachata vs. Kahuna overview in Part 2 below.

Thursday, February 19, 2015

Weather that grinds the soul

Weather the grinds the soul
Precipitation and Surface Map Projections for 7 PM Saturday 
from the NOAA Weather Prediction Center


Wednesday, February 18, 2015

I want the TRUTH!

Squall today, cold tomorrow.

Arctic front traverses eastern Mid-Atlantic between 4 PM and 7 PM, bringing another round of rapid snowfall near the PM commute, accumulating 1-2" in some areas by 7 PM. 

Liquid map for Wed 2/18 shows precip amounts will be light, but ratios will allow for fluffier snow. Similar to Saturday 2/14, roads may become quickly snow-covered and visibility could reduce to one-quarter mile in brief heavy snow squalls during the PM commute. 

  • WED 2/18 - AM temps in near zero to teens throughout the region rise to around 30 F in urban and waterfront areas, holding in low 20s in rural and northern locations. A WINTER WEATHER ADVISORY & WIND CHILL ADVISORY in effect for the Baltimore/Washington metro region from 2 PM to 9 PM tonight per Sterling NWS.

  • THU 2/19 - Much colder, highs dropping back to the teens under clearing skies.
  • FRI  2/20 - Super cold, AM lows below zero for many, highs barely hitting 10 F.
  • WEEKEND - Snow showers possible on Saturday ahead of a developing Low in the Gulf coast. Sunday uncertain, possible light snow north and rain/snow mix in south
  • NEXT WEEK - Continued cold with new indications of another potentially significant winter weather event for the period Feb 22-23 from the Tennessee Valley to the Mid-Atlantic and Northeast.  However, precise details precipitation, intensity and timing are not clear this early in the forecasting process.
*Experimental variation of a long dormant tagline on this site from 2005 when it was known as "Basic Weather For Busy People."

"I want the truth!"
- Lt. Daniel Kaffee played by Tom Cruise, questioning Col. Jessup,  played by Jack Nicholson, in the 1992 film A Few Good Men

3:30 AM 2/17  (Forecaster Mike & the Winter Stormcast Team) Is the truth better even if it's bad news, or can we rest in a little bliss for a while? That would be nice, but the weather pattern probably won't let us. As a deep freeze settles in ahead of a new Arctic front, we look ahead to the next few weeks. Some harsh realities are in store for us as an entire winter's worth of cold has been saved up for the final two weeks of February 2015. 

Monday, February 16, 2015

Catch me if you can.

"Catch me if you can."
- 2002 film starring Leo Dicaprio and Tom Hanks (Youtube trailer)

  • Although decent bands of snow have set up across the region, uncertainty remains as to if the moisture levels of the system north of DC have enough depth to produce totals at the higher end of current ranges.
  • Latest short range guidance as of 7:45 PM indicate dry air to the north is affecting snowfall rates in some areas of northern and eastern Maryland. In addition, the storm does not appear to be showing any further northward movement. 
  • Extremely fine-grained snow flakes/crystals are developing in a level of the atmosphere where temperatures are between 0 and 5 F. Thus, snow ratios in the Washington DC area are estimated by computer models and visual inspection to be near 20:1, and 15:1 in northern MD. 
  • The Winter Stormcast Team anticipates snowfall totals, with exception of DC metro, will stay at the LOWER end of our forecasted ranges for this event. See below for our earlier snowfall map. 

3:00 PM EST 2/16   SNOW ARRIVING IN DC METRO AND SOUTHERN MARYLAND. Further assessment of observations, short range guidance and ground reports indicates the system so far is on track to perform as expected. Dry air is slowly being eroded as moisture levels increase with the eastward approaching precipitation shield. We do not plan to raise or lower totals at this time. 


We are cognizant that other outlets and forecasters have different snowfall totals than our map below, or are evaluating raising amounts ahead of the storm. We respect their choice to make that decision, but disagree on a different set of scientific grounds. 

Our view: Dry air ahead of the approaching precipitation will take a number of hours to overcome to achieve moistening of "the column." Evidence: Dewpoints in the region still below zero as of 1100 AM per NOAA Storm Prediction Center Mesoscale Analysis.
  • Once this saturation level is reached, upper level and surface conditions can permit snow to reach the ground and not evaporate before doing so. However, a combination of recent surface observations and short range models suggests just light snow to start from Northern Virginia to DC and Baltimore by the PM commute. Heavier snow may not arrive until around 12 AM. 
  • This dry air delay could easily reduce totals to the lower end of our ranges. A 1029 mb High pressure in Eastern North Carolina is also not moving out as quickly as expected.
  • If we choose to adjust totals, we will first collect actual observable changes in ground truth once the system produces snow in our forecasted locations, versus using only model guidance. Based on the latest guidance, it is more likely we would hold or lower, not raise expected totals.


It seems that storms this winter in the Mid-Atlantic this has been taking a page from the script written by Frank Abagnale Jr. If you know the incredible story, it recounts the travels of the deceivingly charming but elusive teenager whom outwitted federal officials for years while on a check-kiting scheme across the country. 
But similar to what's next for the Mid-Atlantic, reality (and the FBI) eventually caught up with Frank. The question is, will this storm dash away our hopes of one big snow like the clever thief, or will it give in at the last minute and deliver its secrets for all to see?

Summary of our projections:
  • We project a 70% probability of a significant winter storm, with snowfall exceeding 4" in most locations south of the PA/MD line as indicated in our final map below.
  • The bust scenarios below account for the 30% probability of a surprise and drastic change in the outcome

SYNOPSIS A storm system currently strengthening over the southern Plains will move into the Southeast tonight, and off the Carolina coast by Tuesday morning. 
  • With extremely cold temperatures entrenched over the Mid-Atlantic, this will be a rare all snow event. Temperatures will range from the lower teens in central PA to the mid 20s in southern VA during the storm. 
  • The precise track of this storm will result in a narrow band of significant snow accumulation, reaching some of the largest this winter season.

TIMING Snowfall will begin Monday late afternoon during the evening rush hour for the metros of the Mid-Atlantic. 
  • Snow will move in from west to east. The heaviest snowfall is expected from around 10PM Monday night until 3AM Tuesday morning, before starting to weaken and taper off during Tuesday's morning rush hour.
  • Some wrap-around enhancement can not be ruled out, hence why the NWS has warnings effective to 12 Noon Tuesday.

IMPACTS We are looking at a moderate to high impact event in which all snow that falls will stick. Road conditions will deteriorate Monday evening, become very hazardous Monday night, before improving during the day on Tuesday. Tuesday's temperatures still will only reach the upper 20s. This snow is expected to be of the light and powdery variety, rather than heavy, wet snow.
  • Central Maryland: 4-8" between DC and Baltimore, 3-6" north of Baltimore.
  • Southern MD: 4-8" near DC, 6-10" south.
  • Northern VA: 4-8", Central VA: 6-10"
  • Lower Eastern Shore: 6-10", Upper Eastern Shore: 4-8"
  • I-95 Corridor in DE/NJ: 3-6"
  • Southern Pennsylvania: 2-4"

  • WINTER STORM WARNINGS are in effect fo the areas noted in DARK PINK on the enclosed NWS Advisory Map. Visit the Eastern Regional HQ of the NWS to link to your area's local forecast office for current statements.
  • WIND CHILL WARNINGS and WIND CHILL ADVISORIES expire this morning in Maryland as the brutal cold finally starts to loosen its grip, but will continue longer in PA and points north

BUST SCENARIOS - As always we like to stay one step ahead of Murphy's Law and let you know in advance how this forecast could go wrong. The above scenario is what we believe is "most probable". But there are some things that could emerge throughout the day Monday that may impact our forecast.

  • The Big Bachata (10% Chance): How will a MD snowstorm figure out how not to snow? There is a chance the storm has trouble overcoming extremely dry air in place over the region currently. Dew point temperatures are well below 0ºF, and the storm will need to moisten the column of air before snow reaches the ground. It is possible, that dry air sucks some of the liquid out of this system and "wastes" a lot of the snow, leaving those north of Baltimore with 1-3", 2-5" falling in between Baltimore and DC, and 3-6" for southern MD.
  • The Big Kahuna (20% Chance): As this storm develops offshore, it could also draw in additional moisture as it rapidly strengthens. This would create heavy bands of snow sliding across the Mid-Atlantic and surpassing our expected totals similar to what we saw almost exactly a year ago in February 2014 and on St. Patrick's Day 2014. Widespread amounts of 8-10" could show up between DC and Baltimore with 6-8" north of the city, and some areas in southern Maryland getting up to a foot of snow.
That being said, we do think the scenario outlined in the map is most likely. But since meteorology is not an exact science, it is important to express the uncertainty when it is present.

LAST PLAY OF WINTER? Spring-a-lings might want to stop reading here. Unfortunately the answer is no. A third round of brutal, arctic air is looking increasingly likely for Wednesday-Friday of this week. We will have more on this later, but it is looking possible that the temperatures may rival what we say yesterday and today. The second half of February is making up for lost time this season. Will there be better times in March ahead? Stay tuned for our long range look coming in the next several days.

Winter Stormcast Team: Forecasters Mike N., Connor M., Jason M., Mintong N., Troy A., Jolene W., Advisors Keith K., Dr. Pete W.,  and R. Foot

Sunday, February 15, 2015

Could it be PD 3?

Could it be PD 3?

2:15 PM 2/15 – Our team's latest statement and scenario map for the upcoming Monday into Tuesday Winter Weather potential in the Mid-Atlantic:

OLD MAN WINTER’S NEXT PLAY – After dealing us the snow squalls and the severe wind/cold, the next play is looking like a possible snow event Monday into Tuesday. Yes this is the Tuesday-Wednesday storm we mentioned earlier, but the timeline has accelerated. We have outlined two scenarios we think are possible for this event. If necessary, our snowfall accumulation map will be posted at 5AM Monday morning. 

SYNOPSIS - A low pressure system currently developing over Texas will start to move east tonight. There are two options when it arrives at our entrenched cold air on the east coast. The storm track will determine our impacts. The strength of the high pressure to our northeast will help drive this track. 

SCENARIO A (50%) – The low tracks further north and encroaches into the high pressure to our north, pushing it out to sea. This forces the storm over our extremely cold air here and delivers the largest and highest impact snow storm of the winter. The I-95 corridor could see significant snowfall (4+”) with very cold temperatures throughout, making for a light, powdery snow. Further south, a dangerous sleet/ice/snow event hits the southern Mid-Atlantic. 

SCENARIO B (50%) – In this scenario, the high pressure wins out and drives the storm further south. The low pressure would find a break in the high and go through the middle rather than pushing the whole thing south. This allows an escape route to the south. Light snow would still reach the I-95 corridor, but it would be on par with the magnitude of previous storms this winter season. The heaviest band of snow would be confined further south. 

CAN'T I JUST FLIP A COIN? - Models have been all over the place with this system, flip-flopping every run with huge swings. At this close range to the event, in probability schemes a 50% rating is actually quite high as it represents there is strong enough evidence to suggest that at any given moment in the 24 hour period starting Noon Monday, snow will be likely in the affected region. 

However, we are not going out flag waving here because further changes in the guidance are likely. We will monitor this over the next 15 hours and have another report coming early Monday morning. 

From our perspective, Winter 2014-15 clearly saved all of its big plays for the end of the game. With yesterday’s snow squalls and the brutal cold today reminiscent of last winter, it doesn’t seem like meteorological spring is only 14 days away! Looks like we have a ways to go before that can enter the long range picture.

Winter Stormcast Team: Forecasters Mike N., Connor M., Jason M., Mintong N., Troy A., Jolene W., Advisors Keith K.,and Dr. Pete W., Editor R. Foot