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March Banter 2024


George BM
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Forecast Discussion

Saturday, March 16, 2024 3:28PM EDT

Blizzard Warning in effect from 8AM EDT Sunday, March 17, 2024 until 3PM EDT Monday, March 18, 2024

High Wind Warning in effect from 9AM EDT Sunday, March 17, 2024 until 6PM EDT Monday, March 18, 2024

Hurricane-Force Wind Warning in effect from 2PM EDT Sunday, March 17, 2024 until 6AM EDT Monday, March 18, 2024 (for tidal-Potomac and Chesapeake Bay)

 

Life-Threatening Late-Winter Storm to cripple the region.

Temps are currently holding in the mid-50sF across the DC metro area but are already starting to fall in far northern Maryland as the cold front associated with the strong northern stream system drops south through the region. Temps will plummet out of the 50s and through the 40s and 30s through the evening and reach the lower 20s in many areas by morning as the unusually cold airmass pushes in. As this occurs through the late afternoon and evening hours skies will become overcast both from lift associated with the southward moving cold front and from the strong southern stream system to our south/southwest. There may be enough lift and moisture associated with the front for some light sprinkles and/or a few flurries/light snow showers to develop through the evening before precip slips to the southeast. Northerly winds will become quite gusty during this time with gusts of 25 to 40 mph.

As the strong southern storm system moves toward the coastal Carolinas tonight it will begin to phase with a second powerful northern stream vort diving south from the eastern Great Lakes/ Toronto region leading to strong diffluence over the surface low leading to rapid deepening. The two will pinwheel around each other as they phase bringing the southern storm and associated surface low northwards as rapid deepening takes place allowing snow to overspread the region by morning from southeast to northwest. The snow will quickly become heavy as NE winds increase with gusts to over 50 mph across the region likely by midday. Temperatures during this time will be in the lower 20sF leading to windchills in the single digits. By the late afternoon/evening the surface low will slow down and eventually stall over the Virginia peninsula/ southern Chesapeake Bay area. The surface pressure could be as low as the mid-950s in millibars breaking monthly low-pressure records in that area. Meanwhile, the areas northwest of the surface low (the greater Washington DC and Baltimore metros) will be getting the worst of this storm with blinding snowfall and widespread 60-75+ mph wind gusts w/ 80-90+ mph gusts along the coast of the Bay. In fact, snowfall rates in the heaviest bands will likely be in the 4-6”+/hr range leading to visibilities as low as 50 feet (effectively zero visibility for the sake of argument) from the late afternoon hours through the night and into Monday morning. Temperatures will remain in the 20s throughout the duration of this event with upper teens possible in the higher elevations north and west and temperatures closer to 32F in far southern MD and along the bay where warmer air will be located near the surface low. Windchills during the duration of the event will stay in the single-digits for most w/ negative single-digits in the mountains and lower teens in southern MD and along the bay.

Near-whiteout and conditions and severe wind gusts will still be ongoing by dawn Monday as the low-pressure system slowly pulls northeastwards. Heavy snow will continue through the late morning to midday hours before tapering off from west to east. When all is set and done with total liquid-equivalent precipitation of 4-7”+ across the region, snowfall totals of 4 to 6 FEET will likely be commonplace with snow drifts of as high as 30 feet possible. Areas in southern MD and near the Bay may end up with slightly less (roughly 2 to 4 feet) as the warmer air associated with the low-pressure center cuts down on totals in that area.

This will be the worst blizzard, by far, to impact the region since weather records started in the later 1800s. It will essentially be a high-impact hurricane with snow instead of rain as the main precip-type. People who venture outside during this time may get disoriented and lost in the whiteout conditions and/or get seriously injured by flying debris. Emergency services may not be able to reach you for days should something happen to you outside. This is the DC and Baltimore urban corridor not Lake Tahoe or the Japanese Alps. We’re not equipped with the snow removal equipment that they have. So, if you absolutely must venture outside during the storm no caution that you use would be too extreme given the circumstances.

Temperatures will only rebound to the lower 30s as skies start clearing by mid to late afternoon on Monday.

 

Forecaster Wannabe: George BM

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9 hours ago, George BM said:

Forecast Discussion

Saturday, March 16, 2024 3:28PM EDT

Blizzard Warning in effect from 8AM EDT Sunday, March 17, 2024 until 3PM EDT Monday, March 18, 2024

High Wind Warning in effect from 9AM EDT Sunday, March 17, 2024 until 6PM EDT Monday, March 18, 2024

Hurricane Wind Warning in effect from 2PM EDT Sunday, March 17, 2024 until 6AM EDT Monday, March 18, 2024 (for tidal-Potomac and Chesapeake Bay)

 

Life-Threatening Late-Winter Storm to cripple to region.

Temps are currently holding in the mid-50sF across the DC metro area but are already starting to fall in far northern Maryland as the cold front associated with the strong northern stream system drops south through the region. Temps will plummet out of the 50s and through the 40s and 30s through the evening and reach the lower 20s in many areas by morning as the unusually cold airmass pushes in. As this occurs through the late afternoon and evening hours skies will become overcast both from lift associated with the southward moving cold front and from the strong southern stream system to our south/southwest. There may be enough lift and moisture associated with the front for some light sprinkles and/or a few flurries/light snow showers to develop through the evening before precip slips to the southeast. Northerly winds will become quite gusty during this time with gusts of 25 to 40 mph.

As the strong southern storm system moves toward the coastal Carolinas tonight it will begin to phase with a second powerful northern stream vort diving south from the eastern Great Lakes/ Toronto region leading to strong diffluence over the surface low leading to rapid deepening. The two will pinwheel around each other as they phase bringing the southern storm and associated surface low northwards as rapid deepening takes place allowing snow to overspread the region by morning from southeast to northwest. The snow will quickly become heavy as NE winds increase with gusts to over 50 mph across the region likely by midday. Temperatures during this time will be in the lower 20sF leading to windchills in the single digits. By the late afternoon/evening the surface low will slow down and eventually stall over the Virginia peninsula/ southern Chesapeake Bay area. The surface pressure could be as low as the mid-950s in millibars breaking monthly low-pressure records in that area. Meanwhile, the areas northwest of the surface low (the greater Washington DC and Baltimore metros) will be getting the worst of this storm with blinding snowfall and widespread 60-75+ mph wind gusts w/ 80-90+ mph gusts along the coast of the Bay. In fact, snowfall rates in the heaviest bands will likely be in the 4-6”+/hr range leading to visibilities as low as 50 feet (effectively zero visibility for the sake of argument) from the late afternoon hours through the night and into Monday morning. Temperatures will remain in the 20s throughout the duration of this event with upper teens possible in the higher elevations north and west and temperatures closer to 32F in far southern MD and along the bay where warmer air will be located near the surface low. Windchills during the duration of the event will stay in the single-digits for most w/ negative single-digits in the mountains and lower teens in southern MD and along the bay.

Near-whiteout and conditions and severe wind gusts will still be ongoing by dawn Monday as the low-pressure system slowly pulls northeastwards. Heavy snow will continue through the late morning to midday hours before tapering off from west to east. When all is set and done with total liquid-equivalent precipitation of 4-7”+ across the region, snowfall totals of 4 to 6 FEET will likely be commonplace with snow drifts of as high as 30 feet possible. Areas in southern MD and near the Bay may end up with slightly less (roughly 2 to 4 feet) as the warmer air associated with the low-pressure center cuts down on totals in that area.

This will be the worst blizzard, by far, to impact the region since weather records started in the later 1800s. It will essentially be a high-impact hurricane with snow instead of rain as the main precip-type. People who venture outside during this time may get disoriented and lost in the whiteout conditions and/or get seriously injured by flying debris. Emergency services may not be able to reach you for days should something happen to you outside. This is the DC and Baltimore urban corridor not Lake Tahoe or the Japanese Alps. We’re not equipped with the snow removal equipment that they have. So, if you absolutely must venture outside during the storm no caution that you use would be too extreme given the circumstances.

Temperatures will only rebound to the lower 30s as skies start clearing by mid to late afternoon on Monday.

 

Forecaster Wannabe: George BM

You must have been inspired somewhat by the ongoing Sierra storm for this one! :)

Here's an "off-the-reservation" AFD out of Reno this morning:

https://www.weather.gov/wrh/TextProduct?product=afdrev

They broke the "fourth wall" in some phrases for this edition. 

I'd think with something like you describe, the authorities would implement a curfew. Now there's an AFD that's be a keeper: "We'd urge people to stay inside during this weather emergency, but the authorities with their "shoot-on-sight" curfew have taken care of that one."

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22 minutes ago, Terpeast said:

I miss reading sky-is-falling AFDs with incoming HECS. Reading the reno and sacramento ones brings back a lot of memories

If you have any old AFDs from our blizzards saved please do share them as unfortunately I am too young to have been able to read of them live... 

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7 minutes ago, SnowenOutThere said:

If you have any old AFDs from our blizzards saved please do share them as unfortunately I am too young to have been able to read of them live... 

Go to:

https://mesonet.agron.iastate.edu/wx/afos/list.phtml

They've got AFDs archived even back to 2003. Pretty complete archives for 2016 and 2009-10. Just use the drop-down menus.

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17 minutes ago, SnowenOutThere said:

If you have any old AFDs from our blizzards saved please do share them as unfortunately I am too young to have been able to read of them live... 

Here's the 2016 storm as written by the legendary Paul Kocin.  (For some reason it's been hanging around my hard drive for years)

 

http://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdepd

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST TUE JAN 19 2016

VALID 12Z FRI JAN 22 2016 - 12Z TUE JAN 26 2016

HIGHLIGHTS...

LETS CUT TO THE CHASE. THE MAIN EVENT IN THE MEDIUM RANGE IS THE
POTENTIAL FOR A SIGNIFICANT EAST COAST SNOWSTORM FROM FRIDAY
THROUGH SUNDAY/DAYS 3 TO 5.  THERE HAS BEEN AND CONTINUES TO BE
RELATIVELY GOOD AGREEMENT ESPECIALLY BETWEEN THE MODEL ENSEMBLES.
COMPARING THE OPERATIONAL RUNS TO THE ENSEMBLE MEANS DOES INDICATE
SOME DIFFERENCES THAT ARE SMALL IN THE LARGE SCALE BUT CRUCIAL TO
THE FORECAST.  ALL MODELS SUGGEST THAT MAJOR DEVELOPMENT FOR THIS
SYSTEM WILL OCCUR AS IT MOVES TO THE MID ATLANTIC COAST AND THEN
THE SYSTEM OCCLUDES...BECOMES MORE VERTICAL AND THEN CONTINUES
NORTHEASTWARD WITH THE MOVEMENT OF THE UPPER TROUGH.  WITH THAT IN
MIND...THE STORM WILL LIKELY SLOW IN ITS FORWARD MOVEMENT AS IT
MOVES OFF THE MID ATLANTIC COAST AND THEN WILL LIKELY ACCELERATE
NORTHEASTWARD OR ANOTHER TRIPLE POINT LOW MAY DEVELOP FARTHER
NORTH AND EAST. THE 00Z ECMWF SUGGESTS BOTH SCENARIOS.  IN EITHER
EVEN...THE OVERALL SPEED OF THE SYSTEM IS IMPORTANT TO AFFECT THE
AMOUNT OF SNOW IN ANY ONE AREA.  THIS WILL BE AN IMPORTANT TREND
TO FOLLOW AS THE MORNING MODEL SOLUTIONS START COMING IN.

IN ADDITION...ANY TRENDS EITHER NORTH OR SOUTH WILL IMPACT
SNOWFALL AMOUNTS ALONG THE NORTHERN EDGE OF THE HEAVIEST SNOW AS
WELL AS THE ISSUES OF MIXING/CHANGEOVER ALONG THE SOUTHERN EDGE OF
THE SYSTEM.  THERE HAVE BEEN SUBTLE NORTH/SOUTH SHIFTS WITH THIS
FORECAST BUT WILL HAVE TO BE ASSESSED WHEN THE MORNING MODELS
ARRIVE. THERE HAVEN'T BEEN LARGE CHANGES WITH THE OVERNIGHT CYCLE.

IN GENERAL...THE OPERATIONAL GFS RUNS ARE SLIGHTLY MORE
PROGRESSIVE THAN THE OPERATIONAL ECMWF RUNS. IN PARTICULAR THE 06Z
GFS TRENDED FASTER THAN PREVIOUS RUNS RESULTING IN LOWER SNOWFALL
AMOUNTS DUE TO LOWER SNOWFALL DURATION. THE 00Z UKMET IS SIMILAR
TO THE ECMWF AND TO SOME EXTENT THE GFS BUT THE 00Z CANADIAN WAS
MUCH MORE PROGESSIVE THAN ANY OTHER MODEL AS WELL AS THE CANADIAN
ENSEMBLES.  AS A RESULT...LATER IN THE FORECAST...THE NAEFS MEAN
IS FASTER THAN THE GFS MEAN DUE TO THE CONTRIBUTION OF THE
CANADIAN SOLUTIONS.   AT THIS TIME...THE HIGHEST PROBABILITIES FOR
THE HEAVIEST SNOW BETWEEN THE ISSUES WITH THE NORTHERN EDGE AND
THE SOUTHERN MIX/CHANGEOVER IS CURRENTLY SUGGESTED TO RUN FROM
NORTHERN VIRGINIA TO EASTERN PENNSYLVANIA/NEW JERSEY INTO SOUTHERN
NEW ENGLAND.

TO PUT THIS SYSTEM IN CONTEXT...THE POTENTIAL SNOWFALL
DISTRIBUTION HAS SIMILARITIES TO SEVERAL MAJOR EAST COAST STORMS
IN RECENT PAST INCLUDING THE 5-6 FEBRUARY 2010 SNOWSTORM/THE
JANUARY 1996 BLIZZARD OF 1996 AND THE PRESIDENTS DAY OF FEBRUARY
2003. JANUARY 1996 IS LIKELY TO BE MORE WIDESPREAD/HEAVY BUT ONLY
TIME WILL TELL. THE MECHANISMS COMING TOGETHER FOR A MAJOR
SNOWFALL ARE TEXTBOOK.

IN THE WEST...PRECIPITATION SHOULD WANE ALONG THE COAST DAY 3 INTO
DAY 4...WITH THE NEXT MAJOR PRECIPITATION EVENT EXPECTED ACROSS
THE PACIFIC NORTHWEST BY NEXT MONDAY OR TUESDAY...WITH SEVERAL
INCHES OF LIQUID EQUIVALENT EXPECTED.

CONFIDENCE...

THIS IS A HIGH CONFIDENCE EVENT THIS FAR OUT IN ADVANCE BUT THAT
ALSO SUGGEST THAT SMALL CHANGES CAN HAVE SIGNIFICANT CHANGES TO
IMPACT. THERE IS STILL 3 TO 4 DAYS FROM THE EVENT AND MANY MODEL
SOLUTIONS TO COME.  THERE HAS BEEN EXCELLENT CONTINUITY RELATIVE
TO AVERAGE AND PERHAPS SIMILAR TO WHAT WAS OBSERVED WITH THE
FORECASTS PRIOR TO 5-6 FEBRUARY 2003...WHICH WAS FORECAST AS MUCH
AS 8 DAYS IN ADVANCE.  OTHER STORMS HAVE BEEN MUCH LESS
PREDICTABLE.  THIS MAY BE ONE CASE WITH A HIGH DEGREE OF
PREDICTABILITY BUT WE SHALL SEE.

KOCIN

 
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A couple AFDs from Mount Holly leading up to the Dec 2009 KU. Pretty interesting reads. Seems the Euro sniffed this one out first, as it often did.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1109 AM EST WED DEC 16 2009

.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD IN FROM THE NORTH AND WEST AND
THEN WEAKEN THROUGH THE WORK WEEK. A SYSTEM THAT WILL DEVELOP
NEAR THE GULF OF MEXICO AND MOVE OUT OVER THE ATLANTIC MAY HAVE
SOME EFFECT ON US LATE IN THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
FLURRY ACTIVITY HAS BEEN LIMITED TO THE NORTHWESTERN AREAS OF THE
CWA. A VORT MAX IS EXPECTED TO ROTATE THROUGH THE AREA THIS
AFTERNOON AND AS A RESULT FLURRIES MAY SPREAD SLIGHTLY FARTHER
SOUTH THAN PREVIOUS THINKING. WE HAVE EXTENDED THE CHANCE FOR
FLURRIES INTO THE LEHIGH VALLEY, ALTHOUGH MOST AREAS PROBABLY
WILL NOT SEE TOO MANY FLAKES FALL AS THEY MAY EVAPORATE BEFORE
REACHING THE GROUND. LAKE EFFECT CLOUDS WILL CONTINUE TO STREAM
INTO THE AREA TODAY, AS THE FETCH OFF THE LAKES REMAINS.

WINDS ARE GUSTY AND WILL REMAIN SO THROUGH THE DAY TODAY BEFORE
STARTING TO DECREASE THIS EVENING. 

GUIDANCE TEMPERATURES WERE IN PRETTY GOOD AGREEMENT WITH
CONTINUITY AND WERE ACCEPTED.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
ANOTHER VORT MAX MOVES ACROSS THE AREA TONIGHT WITH SOME
REINFORCING COLD AIR. THE ATMOSPHERE LOOKS TO BE DRIER, SO WE ARE
CONFINING SNOW FLURRIES TO THE NORTHWEST AND GOING MOSTLY CLEAR
ELSEWHERE FOR NOW. WINDS MAY PICK UP SOME AS THE SECONDARY PUSH
OCCURS. GUIDANCE TEMPS AGAIN ARE IN GOOD AGREEMENT WITH CONTINUITY
AND ARE ACCEPTED.

THURSDAY THROUGH FRIDAY LOOKS DRY, ALTHOUGH WARM AIR ADVECTION
ALOFT AND AN UPPER JET MAY BRING SOME MID AND HIGH CLOUDINESS INTO
THE AREA THURSDAY NIGHT INTO FRIDAY. WINDS SHOULD BE DIMINISHING
THROUGH THE PERIOD, AND WERE IT NOT FOR THE POSSIBILITY OF CLOUDS
WE WOULD HAVE UNDERCUT GUIDANCE MINS ON THURSDAY NIGHT WITH
EXCELLENT RADIATING CONDITIONS. AS IT IS, WE CONTINUED TO WALK A
GUIDANCE-CONTINUITY LINE, WHICH HAS WORKED REASONABLY WELL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE MODELS CONTINUE TO DIFFER AS TO HOW THEY HANDLE THE ROTATING
UPPER LOW TO OUR NORTH ALONG WITH THE ASSOCIATED SHARPENING TROUGH. 
AT THE SURFACE, ALL MODELS DEVELOP A LOW ALONG THE SE COAST AND
HEAD IT NE. MOST OF THE MODELS KEEP IT FAR ENOUGH S AND E OF OUR
AREA SO THAT IT JUST BRUSHES OUR SE SECTIONS. THE OUTLIER AT THIS
TIME IS THE ECMWF WHICH SHARPENS THE TROUGH AND DEVELOPS AN INTENSE
EAST COAST STORM. IT IS ALSO MUCH FASTER THAN THE REST OF THE MODELS
AND WOULD HAVE THE BIGGEST IMPACT LATE SATURDAY AND SATURDAY NIGHT
RATHER THAN LATE SATURDAY NIGHT AND SUNDAY. FOR NOW WE WILL GO WITH
THE MAJORITY AND BRING INCREASING CLOUDINESS IN LATE SATURDAY INTO
SATURDAY NIGHT AND CALL FOR A CHANCE OF SNOW INLAND AND RAIN OR SNOW
ALONG THE COAST LATE SATURDAY NIGHT AND SUNDAY. ONCE THE LOW MOVES 
OFF TO THE NE, HIGH PRESSURE WILL BRING ANOTHER BATCH OF COLD AIR 
INTO OUR AREA FOR THE BEGINNING OF NEXT WEEK.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
658 PM EST FRI DEC 18 2009

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OFF TO THE NORTHEAST THIS 
EVENING ALLOWING A MASSIVE LOW PRESSURE SYSTEM TO FILL IN BEHIND 
THIS WEEKEND. THIS LOW PRESSURE WILL BE ARRIVING BY EARLY MORNING 
SATURDAY AND HEADING TO THE NORTHEAST THROUGHOUT THE DAY. THE LOW 
SHOULD PULL FAR ENOUGH TO THE NORTHEAST ON SUNDAY THAT WE WILL SEE A 
BRIEF RETURN OF HIGH PRESSURE ON SUNDAY. THE HIGH PRESSURE WILL GIVE 
WAY TO ANOTHER LOW PRESSURE SYSTEM MOVING IN FROM THE NORTHWEST ON 
MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A 20Z SURFACE ANALYSIS SHOWS AN INTENSE AREA OF LOW PRESSURE OVER 
THE SOUTHEASTERN UNITED STATES WHILE HIGH PRESSURE CONTINUES TO SIT 
OVER THE NORTHEAST. WINDS WILL REMAIN FAIRLY CALM THIS EVENING BUT 
WITH TEMPERATURES WELL BELOW FREEZING WINDS CHILLS WILL BE IN THE 
SINGLE DIGITS TO THE TEENS. WHILE FOLLOWING THE STORM SYSTEM DOWN IN 
THE SOUTHEAST UNITED STATES WE BROUGHT THE ONSET OF PRECIPITATION IN 
WILL START LATE TONIGHT IN THE FAR SOUTHERN ZONES AND PROGRESSIVELY 
SPREAD TO THE NORTH DURING THE DAY.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
AS IF THINGS COULD NOT GET ANY MORE COMPLICATED WITH THIS MASSIVE 
LOW PRESSURE SYSTEM IT APPEARS AS THOUGH THE EARLY MORNING NAM 
LEAVES US HIGH AND DRY...HOWEVER 6 HOURS LATER, WE ARE ONCE AGAIN 
WET. BOTH THE NAM AND ECMWF HAVE BEEN PRETTY GOOD RECENTLY WITH 
THEIR INITIALIZATIONS FIELDS AND OVERALL PERFORMANCE, SO IT IS 
REALLY HARD TO DISCREDIT THEIR RECENT SOLUTIONS. WITH THAT BEING 
SAID, BELIEVE A BLEND OF THE TWO MODELS WOULD PROVIDE THE BEST 
SOLUTION FOR SNOWFALL AMOUNTS ACROSS THE REGION.

UPPER LEVEL DYNAMICS ADD TO THE DEEPENING OF THE LOW PRESSURE SYSTEM 
WHILE IT MOVES TO THE NORTHEAST. OUR CWA IS PLACED IN A GREAT REGION 
BETWEEN A COUPLED 250H JET STREAK TO SEE AN ENHANCEMENT OF UVM 
PROVIDING AN AREA OF MASS DIVERGENCE LEADING TO THE OFFSHORE LOW 
DEEPENING. THE INTERACTION WITH THE MID-LEVEL LOW IS A LITTLE MORE 
PRECARIOUS RIGHT NOW. BOTH MODELS ARE SHOWING SOME SLIGHT PHASING OF 
THE TWO REGIONS LATE SATURDAY WITH THE NAM BEING SLIGHTLY FASTER 
THAN THE EURO. THIS PHASING WOULD PROVIDE AN OVERALL SLOWING OF THE 
SYSTEM AND POSSIBLE OCCLUSION LEADING TO A GREATER CHANCE OF WRAP 
AROUND MOISTURE TO BE SLUNG OVER THE REGION ON SUNDAY. BOTH MODELS 
ALSO HINT AT A SLIGHT TROWAL EVENT WITH A DEFORMATION ZONE TO THE 
NORTHWEST OF THE PHILADELPHIA METRO AREA ALLOWING ENHANCED 
PRECIPITATION TO OCCUR. LOOKS LIKE THE HEAVIEST SNOW WILL BEGIN LATE 
SATURDAY EVENING THROUGH EARLY SUNDAY MORNING SOUTH OF I-95 CORRIDOR 
WHERE THE BEST OMEGA WILL BE MAINTAINED. 

THIS SYSTEMS TRACK HAS BEEN HANDLED FAIRLY WELL WITH PREVIOUS 
FORECASTS AND AMOUNT OF QPF. THIS SYSTEM WILL BE THE FIRST 
WIDE-SPREAD PLOW-ABLE SNOWFALL EVENT IN THIS EARLY SEASON. RECORDS 
SHOW THAT PHILADELPHIA HAS ONLY THREE SEPARATE OCCASIONS IN 
DECEMBER WITH DOUBLE DIGIT SNOWFALLS, 12/26/1909, 12/12/1960, AND
12/24/1966, COULD THIS BE THE FOURTH ONE? ACCUMULATIONS LOOK
STAGGERING WITH AT LEAST AN 8 INCH SNOWFALL IN THE METRO AREA WITH
LOCALLY HIGHER AMOUNTS SOUTH AND EAST OF THE CITY WHERE MESOSCALE
BANDING APPEARS TO HAVE THE BEST CHANCE TO FORM.
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13 hours ago, George BM said:

Forecast Discussion

Saturday, March 16, 2024 3:28PM EDT

Blizzard Warning in effect from 8AM EDT Sunday, March 17, 2024 until 3PM EDT Monday, March 18, 2024

High Wind Warning in effect from 9AM EDT Sunday, March 17, 2024 until 6PM EDT Monday, March 18, 2024

Hurricane-Force Wind Warning in effect from 2PM EDT Sunday, March 17, 2024 until 6AM EDT Monday, March 18, 2024 (for tidal-Potomac and Chesapeake Bay)

 

Life-Threatening Late-Winter Storm to cripple the region.

Temps are currently holding in the mid-50sF across the DC metro area but are already starting to fall in far northern Maryland as the cold front associated with the strong northern stream system drops south through the region. Temps will plummet out of the 50s and through the 40s and 30s through the evening and reach the lower 20s in many areas by morning as the unusually cold airmass pushes in. As this occurs through the late afternoon and evening hours skies will become overcast both from lift associated with the southward moving cold front and from the strong southern stream system to our south/southwest. There may be enough lift and moisture associated with the front for some light sprinkles and/or a few flurries/light snow showers to develop through the evening before precip slips to the southeast. Northerly winds will become quite gusty during this time with gusts of 25 to 40 mph.

As the strong southern storm system moves toward the coastal Carolinas tonight it will begin to phase with a second powerful northern stream vort diving south from the eastern Great Lakes/ Toronto region leading to strong diffluence over the surface low leading to rapid deepening. The two will pinwheel around each other as they phase bringing the southern storm and associated surface low northwards as rapid deepening takes place allowing snow to overspread the region by morning from southeast to northwest. The snow will quickly become heavy as NE winds increase with gusts to over 50 mph across the region likely by midday. Temperatures during this time will be in the lower 20sF leading to windchills in the single digits. By the late afternoon/evening the surface low will slow down and eventually stall over the Virginia peninsula/ southern Chesapeake Bay area. The surface pressure could be as low as the mid-950s in millibars breaking monthly low-pressure records in that area. Meanwhile, the areas northwest of the surface low (the greater Washington DC and Baltimore metros) will be getting the worst of this storm with blinding snowfall and widespread 60-75+ mph wind gusts w/ 80-90+ mph gusts along the coast of the Bay. In fact, snowfall rates in the heaviest bands will likely be in the 4-6”+/hr range leading to visibilities as low as 50 feet (effectively zero visibility for the sake of argument) from the late afternoon hours through the night and into Monday morning. Temperatures will remain in the 20s throughout the duration of this event with upper teens possible in the higher elevations north and west and temperatures closer to 32F in far southern MD and along the bay where warmer air will be located near the surface low. Windchills during the duration of the event will stay in the single-digits for most w/ negative single-digits in the mountains and lower teens in southern MD and along the bay.

Near-whiteout and conditions and severe wind gusts will still be ongoing by dawn Monday as the low-pressure system slowly pulls northeastwards. Heavy snow will continue through the late morning to midday hours before tapering off from west to east. When all is set and done with total liquid-equivalent precipitation of 4-7”+ across the region, snowfall totals of 4 to 6 FEET will likely be commonplace with snow drifts of as high as 30 feet possible. Areas in southern MD and near the Bay may end up with slightly less (roughly 2 to 4 feet) as the warmer air associated with the low-pressure center cuts down on totals in that area.

This will be the worst blizzard, by far, to impact the region since weather records started in the later 1800s. It will essentially be a high-impact hurricane with snow instead of rain as the main precip-type. People who venture outside during this time may get disoriented and lost in the whiteout conditions and/or get seriously injured by flying debris. Emergency services may not be able to reach you for days should something happen to you outside. This is the DC and Baltimore urban corridor not Lake Tahoe or the Japanese Alps. We’re not equipped with the snow removal equipment that they have. So, if you absolutely must venture outside during the storm no caution that you use would be too extreme given the circumstances.

Temperatures will only rebound to the lower 30s as skies start clearing by mid to late afternoon on Monday.

 

Forecaster Wannabe: George BM

Can we take the part out about lower totals near the bay? How about CAPE gets screwed and gets 6" of rain while AA county is in the extreme snowfall rates due to R/S line of Kent Island.  Lollies to 6' along the PG/AA county line. Can I also get some thunder in there?

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3 hours ago, CAPE said:

A couple AFDs from Mount Holly leading up to the Dec 2009 KU. Pretty interesting reads. Seems the Euro sniffed this one out first, as it often did.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1109 AM EST WED DEC 16 2009

.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD IN FROM THE NORTH AND WEST AND
THEN WEAKEN THROUGH THE WORK WEEK. A SYSTEM THAT WILL DEVELOP
NEAR THE GULF OF MEXICO AND MOVE OUT OVER THE ATLANTIC MAY HAVE
SOME EFFECT ON US LATE IN THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
FLURRY ACTIVITY HAS BEEN LIMITED TO THE NORTHWESTERN AREAS OF THE
CWA. A VORT MAX IS EXPECTED TO ROTATE THROUGH THE AREA THIS
AFTERNOON AND AS A RESULT FLURRIES MAY SPREAD SLIGHTLY FARTHER
SOUTH THAN PREVIOUS THINKING. WE HAVE EXTENDED THE CHANCE FOR
FLURRIES INTO THE LEHIGH VALLEY, ALTHOUGH MOST AREAS PROBABLY
WILL NOT SEE TOO MANY FLAKES FALL AS THEY MAY EVAPORATE BEFORE
REACHING THE GROUND. LAKE EFFECT CLOUDS WILL CONTINUE TO STREAM
INTO THE AREA TODAY, AS THE FETCH OFF THE LAKES REMAINS.

WINDS ARE GUSTY AND WILL REMAIN SO THROUGH THE DAY TODAY BEFORE
STARTING TO DECREASE THIS EVENING. 

GUIDANCE TEMPERATURES WERE IN PRETTY GOOD AGREEMENT WITH
CONTINUITY AND WERE ACCEPTED.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
ANOTHER VORT MAX MOVES ACROSS THE AREA TONIGHT WITH SOME
REINFORCING COLD AIR. THE ATMOSPHERE LOOKS TO BE DRIER, SO WE ARE
CONFINING SNOW FLURRIES TO THE NORTHWEST AND GOING MOSTLY CLEAR
ELSEWHERE FOR NOW. WINDS MAY PICK UP SOME AS THE SECONDARY PUSH
OCCURS. GUIDANCE TEMPS AGAIN ARE IN GOOD AGREEMENT WITH CONTINUITY
AND ARE ACCEPTED.

THURSDAY THROUGH FRIDAY LOOKS DRY, ALTHOUGH WARM AIR ADVECTION
ALOFT AND AN UPPER JET MAY BRING SOME MID AND HIGH CLOUDINESS INTO
THE AREA THURSDAY NIGHT INTO FRIDAY. WINDS SHOULD BE DIMINISHING
THROUGH THE PERIOD, AND WERE IT NOT FOR THE POSSIBILITY OF CLOUDS
WE WOULD HAVE UNDERCUT GUIDANCE MINS ON THURSDAY NIGHT WITH
EXCELLENT RADIATING CONDITIONS. AS IT IS, WE CONTINUED TO WALK A
GUIDANCE-CONTINUITY LINE, WHICH HAS WORKED REASONABLY WELL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE MODELS CONTINUE TO DIFFER AS TO HOW THEY HANDLE THE ROTATING
UPPER LOW TO OUR NORTH ALONG WITH THE ASSOCIATED SHARPENING TROUGH. 
AT THE SURFACE, ALL MODELS DEVELOP A LOW ALONG THE SE COAST AND
HEAD IT NE. MOST OF THE MODELS KEEP IT FAR ENOUGH S AND E OF OUR
AREA SO THAT IT JUST BRUSHES OUR SE SECTIONS. THE OUTLIER AT THIS
TIME IS THE ECMWF WHICH SHARPENS THE TROUGH AND DEVELOPS AN INTENSE
EAST COAST STORM. IT IS ALSO MUCH FASTER THAN THE REST OF THE MODELS
AND WOULD HAVE THE BIGGEST IMPACT LATE SATURDAY AND SATURDAY NIGHT
RATHER THAN LATE SATURDAY NIGHT AND SUNDAY. FOR NOW WE WILL GO WITH
THE MAJORITY AND BRING INCREASING CLOUDINESS IN LATE SATURDAY INTO
SATURDAY NIGHT AND CALL FOR A CHANCE OF SNOW INLAND AND RAIN OR SNOW
ALONG THE COAST LATE SATURDAY NIGHT AND SUNDAY. ONCE THE LOW MOVES 
OFF TO THE NE, HIGH PRESSURE WILL BRING ANOTHER BATCH OF COLD AIR 
INTO OUR AREA FOR THE BEGINNING OF NEXT WEEK.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
658 PM EST FRI DEC 18 2009

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO MOVE OFF TO THE NORTHEAST THIS 
EVENING ALLOWING A MASSIVE LOW PRESSURE SYSTEM TO FILL IN BEHIND 
THIS WEEKEND. THIS LOW PRESSURE WILL BE ARRIVING BY EARLY MORNING 
SATURDAY AND HEADING TO THE NORTHEAST THROUGHOUT THE DAY. THE LOW 
SHOULD PULL FAR ENOUGH TO THE NORTHEAST ON SUNDAY THAT WE WILL SEE A 
BRIEF RETURN OF HIGH PRESSURE ON SUNDAY. THE HIGH PRESSURE WILL GIVE 
WAY TO ANOTHER LOW PRESSURE SYSTEM MOVING IN FROM THE NORTHWEST ON 
MONDAY AND TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A 20Z SURFACE ANALYSIS SHOWS AN INTENSE AREA OF LOW PRESSURE OVER 
THE SOUTHEASTERN UNITED STATES WHILE HIGH PRESSURE CONTINUES TO SIT 
OVER THE NORTHEAST. WINDS WILL REMAIN FAIRLY CALM THIS EVENING BUT 
WITH TEMPERATURES WELL BELOW FREEZING WINDS CHILLS WILL BE IN THE 
SINGLE DIGITS TO THE TEENS. WHILE FOLLOWING THE STORM SYSTEM DOWN IN 
THE SOUTHEAST UNITED STATES WE BROUGHT THE ONSET OF PRECIPITATION IN 
WILL START LATE TONIGHT IN THE FAR SOUTHERN ZONES AND PROGRESSIVELY 
SPREAD TO THE NORTH DURING THE DAY.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
AS IF THINGS COULD NOT GET ANY MORE COMPLICATED WITH THIS MASSIVE 
LOW PRESSURE SYSTEM IT APPEARS AS THOUGH THE EARLY MORNING NAM 
LEAVES US HIGH AND DRY...HOWEVER 6 HOURS LATER, WE ARE ONCE AGAIN 
WET. BOTH THE NAM AND ECMWF HAVE BEEN PRETTY GOOD RECENTLY WITH 
THEIR INITIALIZATIONS FIELDS AND OVERALL PERFORMANCE, SO IT IS 
REALLY HARD TO DISCREDIT THEIR RECENT SOLUTIONS. WITH THAT BEING 
SAID, BELIEVE A BLEND OF THE TWO MODELS WOULD PROVIDE THE BEST 
SOLUTION FOR SNOWFALL AMOUNTS ACROSS THE REGION.

UPPER LEVEL DYNAMICS ADD TO THE DEEPENING OF THE LOW PRESSURE SYSTEM 
WHILE IT MOVES TO THE NORTHEAST. OUR CWA IS PLACED IN A GREAT REGION 
BETWEEN A COUPLED 250H JET STREAK TO SEE AN ENHANCEMENT OF UVM 
PROVIDING AN AREA OF MASS DIVERGENCE LEADING TO THE OFFSHORE LOW 
DEEPENING. THE INTERACTION WITH THE MID-LEVEL LOW IS A LITTLE MORE 
PRECARIOUS RIGHT NOW. BOTH MODELS ARE SHOWING SOME SLIGHT PHASING OF 
THE TWO REGIONS LATE SATURDAY WITH THE NAM BEING SLIGHTLY FASTER 
THAN THE EURO. THIS PHASING WOULD PROVIDE AN OVERALL SLOWING OF THE 
SYSTEM AND POSSIBLE OCCLUSION LEADING TO A GREATER CHANCE OF WRAP 
AROUND MOISTURE TO BE SLUNG OVER THE REGION ON SUNDAY. BOTH MODELS 
ALSO HINT AT A SLIGHT TROWAL EVENT WITH A DEFORMATION ZONE TO THE 
NORTHWEST OF THE PHILADELPHIA METRO AREA ALLOWING ENHANCED 
PRECIPITATION TO OCCUR. LOOKS LIKE THE HEAVIEST SNOW WILL BEGIN LATE 
SATURDAY EVENING THROUGH EARLY SUNDAY MORNING SOUTH OF I-95 CORRIDOR 
WHERE THE BEST OMEGA WILL BE MAINTAINED. 

THIS SYSTEMS TRACK HAS BEEN HANDLED FAIRLY WELL WITH PREVIOUS 
FORECASTS AND AMOUNT OF QPF. THIS SYSTEM WILL BE THE FIRST 
WIDE-SPREAD PLOW-ABLE SNOWFALL EVENT IN THIS EARLY SEASON. RECORDS 
SHOW THAT PHILADELPHIA HAS ONLY THREE SEPARATE OCCASIONS IN 
DECEMBER WITH DOUBLE DIGIT SNOWFALLS, 12/26/1909, 12/12/1960, AND
12/24/1966, COULD THIS BE THE FOURTH ONE? ACCUMULATIONS LOOK
STAGGERING WITH AT LEAST AN 8 INCH SNOWFALL IN THE METRO AREA WITH
LOCALLY HIGHER AMOUNTS SOUTH AND EAST OF THE CITY WHERE MESOSCALE
BANDING APPEARS TO HAVE THE BEST CHANCE TO FORM.

@CAPE turned me on to the Mt. Holly discos several years ago. Talented, insightful mets doing their thing up there. Whenever we have interesting LWX wx forecasted....I always check out Mt. Holly's disco to see their spin on it.

2 hours ago, GATECH said:

Nice shout out @jonjon  you have an awesome place with awesome beers.   Nice hats too, my current go to which I got in January.

image.jpeg.f1cd343978d2af746a9e1d06c46f6c6f.jpeg

Adding this to our daytrip list...  :) 

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2 minutes ago, stormtracker said:

Dammit man.  I can't even find one bottle here. 

Catch an Uber and head an hour east. The Winery. Good people. They have em' cold. So you can sip on one and get twisted on the return trip B)

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25 minutes ago, CAPE said:

Friday Happy hour- Sipping a 120 while monitoring 4 webcams from the Sierra Nevada, living vicariously.

@stormtracker

Picked up a 4 pack in Kent Island for 38 bucks. I been jonesin'.

120's are damn near impossible to find in NoVA. Maybe I need to hit up UberEats to see if they'll track it down FOR me....

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40 minutes ago, stormtracker said:

Apparently total wine and spirits has it in Montgomery county

Found quite a few locations within a few miles of you that supposedly have World Wide Stout. Cant go wrong with that. Nothing for the 120s.

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