Thursday, January 31, 2019

2 comments:
Just think... we've had all this,
and it's not even FEBRUARY yet.

UPDATE AS OF 7:30 AM THU 1/31/19


  • RECORD-SETTING COLD will loosen it's zombie-like grip on the Mid-Atlantic by this weekend. But not before a pesky disturbance tries to spook delay-weary school districts on Friday morning. 
  • THE GOOD NEWS is that due to a blanket of dry air in place, and slow movement of the next moisture pulse, we expect any snow to be light, intermittent and reach a  dusting to 1/2 inch at best in most locations east of I-81. The bulk of precip should be lost to evaporation in sub 20 F air conditions. 
  • THE BETTER NEWS, for now, is that a post-cold blast warmup into the 50s and 60s  next week may make Tundra Thursday seem like it was some bad daymare you had while napping.  See below for temperatures next week.
  • HOWEVER, IT'S NOT OVER. Powderhounds and school officials alike may be intrgued to hear this whole snow-cold-warm and back again pattern is expected to completely REPEAT again after the first week of February. This first visit by your vicious little Polar Vortex friend will not be it's last, this winter.

IMAGE CREDIT: Chicago Tribune and Washington Post

Consider this fair warning, when we are basking in semi-tropical conditions next week fully 50-60 degrees warmer than today, it will be a perfect time to stock up on, well, you know.... 






What can a snow squall really do? Take a look at Buffalo...




By next Monday, it will just be a memory -- at least for a couple days. Until Fiery February turns frigid again.


Tuesday, January 29, 2019

5 comments:
How about "Wish I Knew  Wednesday?"

UPDATE AS OF 4:20 AM WED 1/30/19

WEDNESDAY: Surprise Squall Line 10 AM - 2 PM
  • Did you know an Arctic front is coming? If not, you will feel it soon.  Short range computer models are depicting a literal white-out wall knifing through the entire region from 10 AM to 3 PM. Winds will spike to 25-35 mph with higher gusts of 45-50 mph in the mid afternoon, just as a near-instant burst of snow arrives with it. 
  • Wind Advisory in effect from 9 AM to 6 PM today for much of the region, and statements from NWS to expect "heavy snow at times" with reduced visibility and strong gusty winds creating power outages. This is especially concerned with single digit temperatures coming tonight and sub-zero wind chills much of Thursday.
  • On a 2-hour delay? You might be stuck facing an approaching squall line of snow, cold surfaces where salt is not working due to low temperatures, and wind-blown snow reducing visibility right at the time everyone is either heading into school or work, or heading home. This is what we call a multi-hazard high impact event. 

  • From the Sterling VA National Weather Service: "Strong winds may blow down trees and power lines which would result in power outages. Loss of power could be life threatening due to the very cold temperatures. Snow showers or snow squalls could enhance gusty winds and briefly lower visibility, resulting in very hazardous driving conditions, especially near and north of Highway 50."
So now you know, and it won't be a surprise for those like you whom have seen the latest "High Resolution Rapid Refresh" model, (HRRR) shown below. They KNOW how serious a winter squall line CAN be, and recognize it's not something to be dismissed. 

Squall line depicted on short range map for 12 PM Wed 1/30



Now, let's ask ourselves, how could the computer models  bother with depicting a seemingly tiny little stripe of snow around 12 Noon Wednesday? Wouldn't all the dry air squeeze it out to nothing? Since many of you were no doubt wondering that same thing this very evening, here's our answer.


Not if the moisture is traveling WITH the Arctic front, and is tapping high liquid to snow ratios of 20:1 or greater. In that case, just 0.01" of water can produce up to 1/2" of snow. Imagine if it all fell in just 1 hour. For fun, let's say...2 PM. Right before buses start to roll. Wish you knew about this on Tuesday? 

In our 15 years of forecasting here at Foots, we have learned there is ONE THING school districts and other organizations seek to avoid if at all possible when making an opening/closing decision:
  • To announce a 2 hour delay, only to realize after it's much too late, that conditions have conspired against you in the computer models, forcing your hand into an early dismissal, or a closing. 
It is a tricky call all the way around, but we are glad to help work the storms with you, and glad you have found the information useful over the years.

- Forecaster Foot & the Advisory Team
7 comments:
Let's Call It "Tricky Tuesday."
Update as of 5:30 AM ET TUE 1/29


  • AM TO AFTERNOON: The latitude of Interstate 70 in central Maryland expected to be dividing line between areas of mainly snow (Frederick, Carroll, Baltimore, Harford), with areas south of I-70 seeing a rain/snow mix until after 2 PM.
  • BETWEEN 12-2 PM: North of I-70, all precip changes to snow and becomes heavy, with up to 1/2" per hour at times after 2 PM to 4 PM. South of I-70, rain/snow mix will battle a few more hours, then convert to all snow starting 4 PM. If you are not home by 4 PM, consider staying where you are until after 7 PM. Remember the Jan 26, 2011 "Carmageddon" on the JFX? Need we say more.
  • PM COMMUTE: From 4-6 PM, once sun angle is lost, snow should become heavy in all areas from I-66 to central PA. Prepare for extended delays, hazardous travel anywhere north of I-66 in DC, snow-covered roads, plow trucks trying to treat roads, frazzled nerves and occasional hair loss. 
  • WHAT'S NEXT? It gets cold, really really cold. And windy through Thursday. A squall line of snow showers may push through the region Wednesday morning, creating a new round of potential delays and icy conditions, with temperatures around 15 F. See below for previous updates and details on timing.


"When can I see you again?"

Update as of 5:30 AM ET TUE 1/29
  • A three-day period of significant and potentially disruptive winter weather will produce widespread impacts on the Mid-Atlantic region from Tuesday 1/29 through Thursday 1/31. A combination of rain to snow, falling temperatures, Arctic conditions and sub zero wind chills may create hazardous travel conditions at times from Tue AM through Thu PM. Today would be a good day to get done as much as you can in advance of this winter resurgence.
  • TUE 1/29: Fast-moving cold front with ample moisture will cross the region, quickly changing rain to snow in all areas west of I-95 corridor by mid afternoon. Short range models show a period of high snowfall intensity up to 1.0" per hour is possible from northern Virginia through the DC metro and into central Maryland. Map below is generalized conditions expected from 4 PM on, with 00Z Wed = to 8 PM local time. 


  • WED 1/30: Region-wide temperatures holding in teens to low 20s, with winds gusting to 30 mph at times. Any residual water or snowmelt will quickly refreeze, possibly creating icy travel conditions for Wed AM commute.

  • THU 1/31: Arctic front sweeps across the region, with AM temps near 5 F in areas south of I-70, -5 F to 5 F north of I-70 into southern PA, and near 10 F on Eastern shore.  AM Wind Chills -10 F to 0 F for much of central MD, southern PA and 0 F to 5 F above for DC metro / northern Virginia. 

NWS Hourly for Sykesville, MD in Carroll County along I-70 as representative of the expected cold intrusion and wind chills


For readers in area school systems, now you have the explanation behind today's headline, so buckle up and get your schedule ready for a re-do. - Forecaster Foot & the FF Team


Tuesday, January 22, 2019

6 comments:
When is the next one?
  • An "intermission" of southern jet stream-enhanced mild air will overtake eastern third of the U.S. from midweek into Friday, with temperatures trending into the 40s. After this raucous cold, we're not sure if our hearts want to "come back from Havana" anyway until the thermometer at least crosses 32.
  • Brief periods of snow possible Thursday afternoon in the Mid-Atlantic at back edge of departing cold front. Little or no impact expected due to warm air & rainfall prior. Refreezing unlikely as snow should be light, intermittent and roadways mild.
  • By Friday afternoon, a new Arctic High pressure system will be reintroducing a fresh supply of much colder air into eastern U.S. This is a strong indicator for the next storm: Accumulating snow has a better chance when cold air is in place before a system develops. 
ABOVE: Probability that your area exceeds the liquid equivalent of 0.25" in snow or sleet, projected for the Sunday 1/27 into Monday 1/28 time period. A similar map is shown for Day 7, Monday into Tuesday.

BELOW:  Long range projection of general surface low position by early Monday morning 1/28 indicates the potential for a favorable setup of a classic "Nor'easter" type system. 


When you see the whiplash weather coming for February, you may look back on January with fondness for the days when temperatures would go above 32 F for more than one day. 

And, if you're a Powderhound, there is so much fun lurking in the long range, we are sure it will be a delight to behold once we can map out all the possibilities coming up. 

- Forecasters Foot and Wise

Saturday, January 19, 2019

4 comments:
IF ARCTIC AIR IS NOT YOUR THING, 
we recommend one of these, today.


8:00 AM SAT 1/19  With current temperatures in many areas east of the Blue Ridge mountains a few degrees above forecasted levels -- it would seem wise to take full advantage of today and GET STUFF DONE that you prefer not to do when temperatures are 10-15 F. 

For most of Maryland east of I-81 to the 95 corridor and Eastern shore -- as well the DC metro area -- precipitation onset may not occur until at least Noon. This should permit road temperatures to improve into upper 30s, and would reduce potential for ice to develop this afternoon in areas where roads are well above 32 F. 

HOWEVER, THE SUNDAY ICE AGE IS STILL COMING. 

  • The Arctic front is still going to barrel through Sunday morning, dropping temps 30+ degrees in 12 hours or less and dropping below 32 F in most areas by mid morning. Below is an hourly projection for Ellicott City in Howard County MD as a sample location for timing and precipitation types.
  • Untreated roads, which will be many, are going to see standing water quickly refreezing by Noon, despite windy conditions. Doc Brown from Back to the Future would be vindicated,because after the ice develops, some of us won't need any roads on Monday -- or even Tuesday.
  • Winds will rise to 15-25 mph with higher gusts, producing sub zero wind chills for 24+ hours from Sunday afternoon through Monday. It will be the coldest air you've felt beating again your house or apartment in a long time. So consider today as one good chance to get ahead of the cold and wind while you can.
  • Additional details on the 4-day weekend potential in the previous post.
NWS HOURLY FORECAST for Ellicott City in Howard County, MD as the example location for precip timing and temperatures in the region.

FOUR DAY WEEKEND ?
How ice on Sunday could threaten Tuesday
Projected mid-day highs for Martin Luther King, Jr. Day, 2019

  • For the upcoming "Big Wet Kahuna" weekend storm, regardless of if your area receives all snow, snow to rain or a wintry mix -- temperatures region wide will crash 30-40 degrees on Sunday from the 40s to the 10s or lower. 
  • THE SALT PROBLEM: Road crews are not likely to apply salt treatment to many surfaces prior to or during 12+ hours of rain Saturday into Sunday would wash all that chemical and effort away. For areas south of I-70 in Maryland, along the I-95 corridor from Phila to Baltimore & DC - rain changes to snow by Noon on Sunday, as temperatures crash. By nightfall, all the rainfall and snow is flash freezing on parking lots, overpasses, off ramps, secondaries, driveways and everywhere else left untreated.
  • THE COLD PROBLEM: In wake of the storm Sunday night into Monday, temperatures continue dropping to single digits for most locations north of Washington DC. All that standing water freezes solid, and the saturated, slushy ground along with it. Then what happens to temperatures Monday and Tuesday? Almost nothing! Highs Monday for most areas north of DC are 15-20 F. In Pennsylvania, highs may not break 10 F. Monday night, lows dip to single digits again. 
  • THE ICE PROBLEM: Neither Sun, nor Salt nor Shovels nor Spears will be able to dislodge and de-ice what could become a region-wide paralyzing, widespread ice event that will severely impact travel Monday and Tuesday. The good news is, this *probably* won't be the start of the next Ice Age. But for a time, it sure will feel like it...


Thursday, January 17, 2019

4 comments:
I N F I N I T Y  W I N T E R ?
Three weather words for the weekend: 
Monsoon, Whiteout, Glacier. See below for updates.

FOR MARVEL FANS, EVEN THAT VIBRANIUM-INFUSED SHIELD MAY NOT BE ENOUGH PROTECTION FROM THE WICKED RAIN, SNOW & COLD THAT'S COMING.


Update as of 5:30 AM ET Thu 1/17

  • THU PM - FRI AM: For most areas from the DC metro to Baltimore metro & the PA line- Light accumulating snow is expected late this afternoon into the PM commute. Snow may fall at a moderate pace for several hours, continue overnight and being tapering toward daybreak. At least 1.0" of snow is likely, and with recent snowpack in place, a chilled surface may reduce loss of the first 1/2", providing for many areas to reach 2" or slightly more.  Below is Mount. Airy, MD in Carroll County as representative location for the region, to indicate timing and general amounts.


  • SATURDAY ( THE MONSOON) For most of the region, precip begins as rain and snow mixed or a period of snow, then turns to mostly rain as temperatures rise well above 32 F ahead of an Arctic front. Late Saturday into Sunday, potentially torrential rain is possible during embedded cells. Up to 1.5 inches of liquid is possible in this period.
  • SUNDAY (THE WHITEOUT?) As the Arctic front crosses the area, temperatures near 40 F around Noon will rapidly drop to the low teens before midnight. Rain in the morning will switch back to snow by 2 PM and could become heavy at times, producing even whiteout or blizzard-like conditions. Have your umbrella, popcorn and water proof phone ready for the weathertainment to come. THEN, all that leftover water seeping everywhere across roads, parking lots, sidewalks and your front step? It will FLASH FREEZE and be a solid block of ice before daybreak. This sets the stage for...
  • MONDAY (THE GLACIER!) With temps between 5-10 F, and no pre-treatment on roads, and all that water having frozen, it's a good thing Monday is a holiday. We think most area roads will be a complete sheet of ice. The safest thing to do is stay home if you don't have to work. With temperatures holding below 20 F until late Tuesday, we wonder how road & grounds crews will prepare buses, lots and sidewalks given that salt treatment generally is much less effective at very low temperatures.
  • BY THEN, YOU'LL HAVE a Captain America or Wonder Woman-level of fortitude to conquer the Infinity Winter that is coming next... (Click image for a larger version)




And if you're a snow plow operator, you'll be saying this a lot the next 2 weeks.

Tuesday, January 15, 2019

6 comments:
"Ohhh, it's Saturday night..."
- lyrics from Say Amen (Saturday Night) by Panic! at the Disco
  • Ready for real winter? The 1/12-13 storm was just the starting point of what will become a Big Kahuna-packed two weeks or more of multiple winter weather & severe cold threats for much of the northern & eastern United States.
  • This Thursday's spritz of light snow/wintry mix in the overnight hours to Friday morning is akin to a "cover band" before the featured singer (the much bigger storm) takes the mic this coming Saturday night. Below is the NWS hourly chart for Eldersburg, MD as a representative location on timing in the region for when light  accumulating snow and sleet is expected to occur:

  • The big reveal: At this point in winter, it appears the Mid-Atlantic is entering an "every 3 days" pattern  of storm events, with Saturdays the center stage for each opening night of the next big snow show. Below, early probabilities for this weekend of possible winter wickedness are already at 30-50% across a massive swath of the northern U.S.  
This map is the Day 7 Winter Weather Outlook from the NOAA Weather Prediction Center. It shows that long range expectations are already increasing for this next system to exceed 0.25" of frozen precipitation through next Sunday morning.




So it might be a good idea to be praying for the wicked this weekend, because what's coming will need some divine intervention so there's no panic at the winter weather disco.  

Then again, once you see the show for yourself, you'll understand why we're concerned. Unless you have fond memories of January 1994.  -Forecaster Foot 

Sunday, January 13, 2019

3 comments:
How Much Longer & What About Monday?
UPDATE AS OF 10:45 AM ET SUN 1/13

  • NORTH OF THE PA LINE, LIGHT TO MODERATE SNOW CONTINUES THROUGH 7 PM BEFORE TAPERING TOWARD MIDNIGHT, WITH AN ADDITIONAL 2" 
  • FOR NORTHERN MD COUNTIES TO I-70/BALTIMORE CITY LINEMODERATE SNOW CONTINUES THROUGH 5 PM, THEN BECOMING LIGHTER AT TIMES AFTER SUNDOWN, WITH AN ADDITIONAL 4-5" AND STORM TOTALS OF 5-10" LIKELY.
  • FROM BALTIMORE CITY SOUTH TO DC METRO INCL. MONTGOMERY, ANNE ARUNDEL, PRINCE GEORGES, MODERATE SNOW TO CONTINUE THROUGH 10 AM, THEN BECOME HEAVY THROUGH 4 PM, WITH AN ADDITIONAL 4-6" PROBABLE IN MOST LOCATIONS, WITH 10" OR MORE LIKELY. TAPERING TO LIGHT SNOW AFTER 10 PM.
  • FOR THE EASTERN SHORE, HEAVY SNOW WILL CONTINUE AT A STEADY PAVE THROUGH NIGHTFALL, WITH WIDESPREAD 4-8" TOTALS FOR ALL AREAS NORTH OF OCEAN CITY. AREAS NEAREST THE BAY MAY EXCEED 8" BY 6 PM TODAY, WITH ACCUMULATING SNOW ENDING BY MIDNIGHT.
  • FOR ALL AREAS: SOME DECREASE TO LIGHT AND MODERATE SNOW INTENSITY EXPECTED FROM AROUND 6 PM, WITH SNOW STARTING TO EXIT THE REGION AROUND 10 PM. ACCUMULATING SNOW SHOULD END BY 12 AM, AND WITH TEMPERATURES REMAINING BELOW 32 MOST OF THE DAY, REFREEZING WILL QUICKLY DEVELOP BY SUNDOWN WITH LOWS IN MID 20S REGION-WIDE. 
  • ABOUT MONDAY: hWell, considering that Winter Storm Warnings were just extended to 12 AM Monday for most locations-- we think tomorrow is largely done for most schools and colleges. The NWS hourly chart above is from Parkville, MD a representative location for the region to illustrate that scattered light snow is still possible in some areas until at least 11 PM tonight. An upper level disturbance is expected to pass through in the final hours, and this would briefly enhance any last snow showers to produce up to 1/2" extra in the 8-11 PM period. This indicates icy conditions should be expected for the AM commute beyond major highways & beltways, specifically in backstreet roads, secondaries, bridges, overpasses and off ramps.
  • PLOWS & LOTS: Many plow operators may need to make three full passes for removal due to the extended duration of this event. If a late stage accumulation occurs, they would have to come back for a 4th pass. Crews working on school & bus lots will have to decide if there is adequate time to make one full cleanup once snow ends this evening, or should they start early knowing a second full pass will be needed before Monday morning?
  • SHORT RANGE SIMULATED RADAR: Snow exiting the 95 corridor around 11 PM as shown below in the High Resolution Rapid Refresh (HRRR) model.

Saturday, January 12, 2019

IF IT'S MEANT TO BE, IT'LL BE

15 comments:
A Weekend of "White in the Winter Night" 

7:15 PM ET SAT 1/12 UPDATE








  • WINTER STORM WARNINGS RAISED FOR MOST OF BALTIMORE-WASHINGTON METRO AREA FROM SATURDAY LATE AFTERNOON THROUGH 6PM SUNDAY FOR 4-8" OR MORE OF SNOW. 
  • DC METRO AND NORTHERN VIRGINIA MAY EXCEED 8" IN AREAS WHERE HEAVIEST SNOW OCCURS EARLY SUNDAY MORNING.
  • SHORT RANGE MODELS SHOW INCREASING POTENTIAL FOR A LATE SUNDAY PM SNOW SQUALL TO CROSS THE I-66 CORRIDOR AREA, PRODUCING AN ADDITIONAL 1/2-1"
  • BESIDES, if you're a Powderhound, isn't this is what we live for, right? Expecting snow and then finding out that your area has been UPGRADED to a WARNING! Golden.
  • SPECIAL NOTE ABOUT THE FORMER INSIDER APP: The Insider App program, operational during the 2015-2017 period is unfortunately no longer available. We do not yet have a projection on if or when this will resume, but are grateful for the generous support and readership many of you devoted to app in those years.
SNOWFALL TIMING & AMOUNTS

  • SATURDAY: Light snow developing in DC metro area/northern VA between 2-3 PM, in Baltimore metro from 3-4 PM, northern MD/PA line by 5 PM. Intensity will pickup into the evening as the eastward moving energy is transferred to a developing coastal low off North Carolina.
  • SATURDAY PM  - SUNDAY AM : Snow intensity region-wide for all areas will increase toward nightfall and continue overnight. This includes a region from the DC I-66 corridor north to the PA I-76 turnpike and east to the Chesapeake Bay & the Eastern shore of MD/DE. Up to 3" is probable by daybreak Sunday for these areas. Sunday AM activities including worship services likely to be impacted. Areas south of I-70 may receive 4" or more where heavier bands develop.
  • SUNDAY PM - MONDAY AM : Snow begins tapering south to north, ending in DC metro by Sunday noon, Baltimore metro region in mid afternoon,and southern PA/Eastern shore by sundown. With sub 30 F temperatures overnight Sunday and powdery snow composition refreezing on untreated surfaces, it is likely that travel delays and some disruptions will occur for the Monday AM commute. For schools, if a second round of snow occurs after grounds crews have cleared lots and prepared buses, Monday may be a challenging situation depending on one's location.
  • LET'S SEE WHERE THIS THING GOES... Short range computer models guidance continues to indicate that higher totals are possible, due either to moisture enhancement from the eventual coastal system, higher snowfall ratios due to cold air, or a northern creep of higher moisture levels. Any of these would result in surprise increases of 1-2" in snowfall totals in the final 6 hours of this event.

EARLIER MAPS & UPDATES BELOW

  • REPRESENTATIVE COMPUTER MODEL GUIDANCE FOR SNOWFALL SAT PM - SUN