999
FOUS11 KWBC 170624
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 AM EDT TUE MAR 17 2026
VALID 12Z TUE MAR 17 2026 - 12Z FRI MAR 20 2026
..GREAT LAKES SOUTHEAST THROUGH THE MID-ATLANTIC
DAY 1...
STRONG LOW PRESSURE WHICH PRODUCED THE BLIZZARD OVER THE UPPER
MIDWEST/WESTERN GREAT LAKES WILL BE WELL NORTHEAST INTO CANADA THIS
MORNING, WHILE ITS TRAILING ARCTIC COLD FRONT WILL BE POSITIONED
JUST OFF THE ATLANTIC SEABOARD TO START THE PERIOD. BEHIND THIS LOW
AND THE ASSOCIATED FRONT, STRONG CAA ON NW WINDS WILL BE WIDESPREAD
ACROSS THE GREAT LAKES, CENTRAL APPALACHIANS, AND MID-ATLANTIC
STATES, WHILE A LAGGING BUT POTENT UPPER TROUGH SWINGS THROUGH THE
OHIO VALLEY. THE OVERLAP OF THIS UPPER TROUGH AND THE POST-FRONTAL
NW FLOW WILL RESULT IN 3 AREAS OF MODERATE TO HEAVY SNOWFALL TODAY.
1) GREAT LAKES: CAA ON THE NW CYCLONIC FLOW WILL DROP 850MB TEMPS
TO AS LOW AS -20C (OR SLIGHTLY COLDER). THIS COLD AIR MOVING ACROSS
THE LAKES WILL LEAD TO VERY STEEP LAPSE RATES AND RISING INVERSION
DEPTHS DESPITE LAKE SURFACE TEMPERATURES THAT ARE GENERALLY +5C OR
LESS ACCORDING TO GLERL. THIS WILL SUPPORT EFFICIENT LAKE EFFECT
SNOW (LES) IN THE FAVORED W/NW SNOW BELTS, AND ALTHOUGH THE
DURATION OF ANY SINGLE BANDS MAY BE MODEST DUE TO THE MOVEMENT OF
THE MID- LEVEL TROUGH, HEAVY SNOW RATES IN EXCESS OF 1"/HR ARE
POSSIBLE (30-50%) WITHIN ANY LES BANDS. THE HEAVIEST ACCUMULATIONS
ARE LIKELY ACROSS THE TUG HILL PLATEAU AND THEN DOWN TOWARDS
SYRACUSE, WHERE WPC PROBABILITIES ARE HIGH (>70%) FOR AT LEAST 4
INCHES OF SNOW, WITH LOCALLY MORE THAN 8 INCHES POSSIBLE.
2) CENTRAL APPALACHIANS: THE PERSISTENT NW FLOW WILL GENERALLY
RESULT IN A DRYING COLUMN ACROSS THE AREA. HOWEVER, AS THE MID-
LEVEL TROUGH SWINGS OVERHEAD, IT WILL BRIEFLY PROVIDE SOME
ADDITIONAL SYNOPTIC ASCENT THROUGH HEIGHT FALLS/PVA, OVERLAPPING
FAVORABLE UPSLOPE FLOW INTO THE TERRAIN TO PRODUCE PERIODS OF
MODERATE TO HEAVY SNOW. THE NATURE OF THIS SNOW MAY BE MORE SNOW
"SHOWERY" THAT CONTINUOUS, LIMITING ACCUMULATIONS OVERALL. HOWEVER,
SNOWFALL RATES MAY AT TIMES REACH 1"/HR (10-30% CHANCE) LEADING TO
LOCALLY AS MUCH AS 4 INCHES OF SNOW (10-30% CHANCE) IN THE HIGHER
TERRAIN OF WV AND INTO THE LAUREL HIGHLANDS OF PA.
3) OHIO VALLEY TO THE MID-ATLANTIC: AS THE MID-LEVEL TROUGH SWINGS
OVERHEAD THIS AFTN/EVE, IT WILL LIKELY ENCOURAGE SOME BUBBLING OF
CONVECTIVE SNOW SHOWERS AND ISOLATED SNOW SQUALLS ACROSS THE
REGION. LAPSE RATES BECOME IMPRESSIVELY STEEP BENEATH THIS TROUGH,
AND THERE WILL BE JUST ENOUGH MOISTURE TO GENERATE NUMEROUS
CONVECTIVE SNOW SHOWERS WHICH WILL MOVE RAPIDLY EAST THROUGH THE
EVENING. THE SNSQ PARAMETER IS HIGH FOR OH/WV/PA, AND LESSER DUE TO
DRIER AIR FARTHER EAST. WHILE SNOW SQUALLS CAN'T BE RULED OUT,
THIS IS MORE LIKELY TO MANIFEST AS SCATTERED TO NUMEROUS CONVECTIVE SNOW
SHOWERS ACROSS THE AREA. ACCUMULATION FROM THESE WILL BE MINIMAL,
BUT BRIEF HEAVY SNOW RATES AND GUSTY WINDS COULD CAUSE RAPID
CHANGES IN VISIBILITY AND HAZARDOUS DRIVING LATER TODAY.
THE PROBABILITY FOR SIGNIFICANT ICING ACROSS THE COUNTRY IS LESS
THAN 10%.
WEISS
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