467
FOUS11 KWBC 182107
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
407 PM EST SAT JAN 18 2025
VALID 00Z SUN JAN 19 2025 - 00Z WED JAN 22 2025
..GREAT LAKES
DAYS 1-3...
DEEP LOW PRESSURE CENTERED OVER NORTHERN ONTARIO WILL MAINTAIN
CYCLONIC FLOW WITH ARCTIC COLD OVER THE GREAT LAKES THROUGH AT
LEAST TUESDAY. NWLY FLOW PREVAILS THROUGH SUNDAY BEFORE BACKING
WLY SUNDAY NIGHT THROUGH MONDAY. 72HR SNOW PROBABILITIES FOR >12"
ARE OVER 50% IN THE WESTERN U.P., NORTHERN AND SOUTHERN WESTERN
SHORES OF THE L.P. AND OVER 80% FOR THE EASTERN U.P.
THE SHIFT TO WESTERLY FLOW OVER THE EASTERN GREAT LAKES ALLOWS
SINGLE BANDING TO DEVELOP BY MONDAY AFTERNOON WITH HEAVY SNOW
PERSISTING INTO TUESDAY NIGHT FOR BUFFALO AND THE SOUTH TOWNS AS
WELL AS NORTHERN SECTIONS OF THE TUG HILL WHERE DAY 3 SNOW
PROBABILITIES FOR >8" ARE OVER 60% (80% FOR THE TUG HILL).
..SOUTH-CENTRAL PLAINS
DAY 2...
THE APPROACHING LONGWAVE TROUGH THAT WILL CAUSE WINTRY WEATHER
ALONG THE GULF COAST (SEE SECTION BELOW) WILL CAUSE SNOW BANDING
EAST FROM THE SOUTHERN CO/NORTHERN NM ROCKIES IN A SIMILAR MANNER
TO THE BANDING THAT OCCURRED TODAY EAST OF THE ROCKIES (NOT THE
HEAVY SNOW IN THE TERRAIN LAST NIGHT) ON MONDAY. DAY 2 SNOW
PROBABILITIES FOR >2" ARE 20-60% OVER SW KS EXTENDING INTO WESTERN
OK.
..CENTRAL APPALACHIANS, MID-ATLANTIC AND NORTHEAST
DAYS 1-2...
...SIGNIFICANT WINTER STORM TO PRODUCE A SWATH OF HEAVY SNOW FROM
THE CENTRAL APPALACHIANS THROUGH THE NORTHERN MID-ATLANTIC AND NEW
ENGLAND SUNDAY THROUGH SUNDAY NIGHT...
THE MAIN GUIDANCE CHANGES TODAY ON THE NORTHEAST WINTER STORM ARE
WITH A SLOWER TIMING. RAP BASED GUIDANCE (HRRR) HAS INCREMENTALLY
SLOWED WITH EACH RECENT RUN SINCE YESTERDAY WHILE THE NAM BASED
MODELS REMAIN ON THE SLOWER END. MEANWHILE A SLIGHTLY FARTHER EAST
SOLUTION IS SEEN FOR NEW ENGLAND IN THE EC AND 18Z HRRR MODELS
WHICH WOULD ALLOW HEAVIER SNOW A BIT FARTHER EAST THAN BEFORE.
THE ARCTIC COLD FRONT WILL PUSH OFF/TO ALONG THE NORTHEASTERN
SEABOARD TONIGHT WHILE STALLING OVER THE CAROLINAS AS THE SURFACE
WAVE TRACKS TOWARD CAPE HATTERAS THROUGH SUNDAY MORNING. THIS WAVE
RAPIDLY DEVELOPS AS IT TRACKS NORTH ALONG THE FRONTAL ZONE THROUGH
SUNDAY NIGHT, REACHING THE CANADIAN MARITIMES BY 12Z MONDAY. STRONG
UPPER- LEVEL DIVERGENCE INCREASES OFF THE MID-ATLANTIC COAST
THROUGH SUNDAY MORNING AS THE SWLY 250MB JET EXCEEDS 150KT WITH
DIFFLUENT LEFT- EXIT REGION AIDING THE RAPID SURFACE/COASTAL
DEVELOPMENT. AS 850-700MB WAA INCREASES OVER THE MID- ATLANTIC, IT
WILL CLASH WITH THE APPROACHING ARCTIC AIR- MASS TO THE NORTH,
RESULTING IN A BAND OF HEAVY SNOW THAT INITIALLY STARTS OUT OVER
THE ALLEGHENY HIGHLANDS EARLY SUNDAY MORNING, THEN SPREADS OVER THE
LAURELS IN PA ACROSS NORTHERN VA AND MD THROUGH MIDDAY (WHICH IS A
LATER TIMING BASED ON THE SLOWED GUIDANCE). EASTERN PA THROUGH
SOUTHERN NY SEE GREAT INCREASES IN 850-700MB FGEN THROUGH THE
AFTERNOON ALLOWING SNOWFALL RATES TO INCREASE THROUGH THIS SWATH.
THE 12Z HREF MEAN HOURLY SNOWFALL HITS 1"/HR OVER THE NORTHERN HALF
OF NJ BY 00Z MONDAY WITH 1"/HR RATES IN A RATHER WIDE SWATH
TRACKING NORTH THROUGH THE NIGHT UNTIL IT CLEARS EASTERN MAINE AT
12Z. THE STORM RACES NORTH THROUGH NEW BRUNSWICK EARLY MONDAY
MORNING WITH LINGERING PERIODS OF SNOW THROUGHOUT PARTS OF MAINE
TAPERING OFF BY MIDDAY MONDAY.
DAY 1.5 WPC SNOW PROBABILITIES FOR >6" SNOW ARE 40-70% OVER CENTRAL
WV TERRAIN AND OVER SOUTHERN PA THROUGH MAINE WITH 50% PROBS FOR
>4" OVER FAR NORTHERN VA/NORTHERN MD, THE PHILLY AND NYC METROS AS
WELL AS A STRIPE OF SOUTHEAST NEW ENGLAND GENERALLY WEST FROM
PROVIDENCE, RI. HAZARDOUS DRIVING CONDITIONS ARE ANTICIPATED IN
THESE AREAS ON SUNDAY. WITH BITTERLY COLD TEMPERATURES SPILLING IN
FOR THE UPCOMING WORK-WEEK, SNOW AND INSTANCES OF RE-FREEZING/BLACK
ICE ARE LIKELY TO STICK AROUND FOR MUCH OF THE WEEK IN WAKE OF
THIS WINTER STORM.
..TEXAS, GULF COAST, AND DEEP SOUTH
...DISRUPTIVE WINTER STORM GROWING IN CONFIDENCE ACROSS THE
SOUTHERN U.S. NEXT WEEK...
DAYS 2/3...
EXCEPTIONALLY COLD/DRY AIR PLUNGES THROUGH TEXAS TONIGHT,
EXPANDING EAST OVER THE GULF COAST THROUGH SUNDAY NIGHT. THIS SETS
THE STAGE FOR WINTRY PRECIP TO DEVELOP IN SOUTH TEXAS MONDAY AS AN
APPROACHING TROUGH AXIS OVER THE FOUR CORNERS ALLOWS A LOW LEVEL
INVERTED TROUGH TO DEVELOP OVER THE WESTERN GULF, CAUSING AN
ONSHORE FLOW TO DEVELOP AND RIDE OVER THE LOW LEVEL COLD ALONG AND
INLAND OF THE LOWER TX COAST. THIS TROUGH CONTINUES TO DEVELOP
THROUGH MONDAY NIGHT WITH PRECIP EXPANDING UP THROUGH CENTRAL AND
INTO NORTH TEXAS AND SOUTHWEST LOUISIANA BY 12Z TUESDAY. SNOW CAN
BE EXPECTED OVER CENTRAL TX AND NORTH WHILE AN ICY WINTRY MIX CAN
BE EXPECTED OVER SOUTH-CENTRAL AND INTERIOR LOWER TX THEN ALONG THE
TX AND LA COASTS.
THE TROUGH AXIS REACHES THE TX COAST TUESDAY EVENING WITH RAPID
EASTWARD EXPANSION EXPECTED TO THE WINTRY MIX THROUGH THE DAY
TUESDAY, LIKELY REACHING THE FL PANHANDLE BY TUESDAY EVENING.
MODERATE TO LOCALLY HEAVY SNOW BANDING IS EXPECTED FROM ROUGHLY
NORTH OF THE HOUSTON METRO EAST ACROSS SOUTHERN LA INTO SOUTHERN MS
ON TUESDAY WITH NOTABLE SNOWFALL FOR THESE AREAS. DAY 3 SNOW
PROBABILITIES FOR >4" ARE 30-60% THROUGH THIS ZONE. THE CONCEPTUAL
MODEL IS FOR A STRIPE OF SLEET AND FREEZING RAIN TO BE SOUTH OF THE
SNOW. AS CURRENTLY DEPICTED THOSE STRIPES LOOK TO BOTH BE ON OR
INLAND FROM THE GULF COAST. DAY 3 ICE PROBABILITIES FOR >0.1" ARE
CURRENTLY AROUND 10% IN BOTH SOUTHERN LA AND JUST SOUTH OF I-10 IN
SOUTH-CENTRAL TX, NORTH OF CORPUS CHRISTI. DETAILS WITH P-PTYPE ARE
BETTER DONE WITH HIGHER-RES MODELS WHICH OFFER OUTPUT IN THE DAYS
1/2 TIMEFRAME, SO EXPECT GREATER DETAIL TO THESE WINTRY
ACCUMULATIONS AT THAT TIME.
PLEASE BE SURE TO VISIT WPC'S MEDIUM RANGE DISCUSSION AND OUR KEY
MESSAGES FOR MORE DETAILS ON THE IMPACTS THAT WILL EXTEND THROUGH
MUCH OF THE SOUTHEAST THROUGH WEDNESDAY.
JACKSON
..WINTER STORM KEY MESSAGES ARE IN EFFECT AS LINKED BELOW
SOUTHERN/GULF COAST WINTER STORM...
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_1.PNG
NORTHEAST WINTER STORM...
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_2.PNG
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