037
FOUS11 KWBC 130906
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
406 AM EST SAT DEC 13 2025
VALID 12Z SAT DEC 13 2025 - 12Z TUE DEC 16 2025
..NORTH-CENTRAL PLAINS, MIDWEST TO THE CENTRAL APPALACHIANS
DAY 1...
LOW TO MID-LEVEL LOW IS OVER NORTH SHORE OF LAKE SUPERIOR WITH A
REINFORCING SHORTWAVE TROUGH OVER FAR NORTHEAST MT. THIS WAVE IS
RIDING A POWERFUL 140KT JET THAT EXTENDS ACROSS THE MIDWEST AND
THROUGH THE MID- ATLANTIC. INTENSIFYING FGEN (BOTH THROUGH WAA AND
THE RESULT OF THE UPPER JET STREAK POSITION) WILL BE SUFFICIENT TO
DRIVE OMEGA THROUGH THE SNOW GROWTH ZONE THROUGH THIS EVENING.
WITH STRONG LIFT OCCURRING INTO A DGZ THAT IS DEEPENING IN THE COLD
AIRMASS, PERIODS OF HEAVY SNOW ARE EXPECTED, ESPECIALLY WITHIN A
NARROW TRANSLATING BAND FROM IOWA THROUGH OHIO AND NORTHERN WV
TODAY. FORCING IS STRONG ENOUGH TO WARRANT A RISK FOR THUNDERSNOW
PARTICULARLY MIDDAY/EARLY AFTERNOON OVER CENTRAL IL/IN WHERE 1"/HR
RATES ARE POSSIBLE PER THE 00Z HREF.
THE BANDS RISE OVER THE ALLEGHENY PLATEAU THIS EVENING WHERE
OROGRAPHY ONCE AGAIN BRINGS A RISK FOR 1"/HR RATES. DAY 1 PWPF FOR
>6" ARE AROUND 10% IN CENTRAL IL/IN AND QUICKLY INCREASE FROM 40%
TO 70% ACROSS FAR SOUTHEAST OH THROUGH NORTH-CENTRAL WV. SNOW RATES
DROP OFF SUNDAY MORNING OVER THE CENTRAL APPALACHIANS, BUT THE
UPPER TROUGH DOES CROSS MIDDAY, SO CONTINUED UPSLOPE SNOW SHOWERS
CAN BE EXPECTED AT LEAST THROUGH THE DAY LIGHT HOURS.
..MID-ATLANTIC THROUGH SOUTHERN NEW ENGLAND
DAYS 1/2...
UPPER LOW STALLS OVER NORTHERN LAKE SUPERIOR TODAY BEFORE EJECTING
SOUTHEAST TONIGHT WITH THE AID OF A REINFORCING SHORTWAVE. THE
RESULTANT UPPER TROUGH AXIS REACHES THE NORTHEASTERN SEABOARD
SUNDAY EVENING WITH DOWNSTREAM SURFACE TROUGH THEN LOW DEVELOPMENT
OFF THE MID-ATLANTIC COAST SUNDAY MORNING. RIGHT ENTRANCE DYNAMICS
AID FGEN BANDING TO DEVELOP IN THE LEE OF THE CENTRAL APPS LATER
THIS EVENING, MOST LIKELY OVER NORTH-CENTRAL MD EAST THROUGH NJ
BEFORE THE SURFACE TROUGH/LOW OFFSHORE PROVIDES ADDITIONAL FORCING
FOR MORE INTENSE BANDING OVERNIGHT TO SHIFT SOUTH AND EAST. THIS
SYSTEM IS FAIRLY PROGRESSIVE, BUT THE FRONTAL FORCING IN
INCREASINGLY COLD AIR ALLOWS 0.75"/HR RATES IN THE MID-ATLANTIC,
EXTENDING TO SOUTHERN NEW ENGLAND EARLY SUNDAY. MARGINAL THERMALS
AT THE SOUTHERN EXTEND OF THE PRECIP SWATH TO BEGIN WITH QUICKLY
SHIFT TO ALL SNOW - THIS IS AIDED THE NIGHTTIME OCCURRENCE.
THIS EVENT SHOULD LAST NO MORE THAN 12 HOURS IN ANY GIVEN LOCATION,
AND THE EXACT PLACEMENT, TIMING, AND INTENSITY OF THE JET STREAK
AND OFFSHORE TROUGH WILL DETERMINE WHERE THE HEAVIER BANDS SETUP
AND PIVOT. DAY 1.5 PWPF FOR >6" ARE OVER 10% FROM JUST NORTH OF DC
THROUGH CAPE CO WITH A PEAK OF AROUND 30% FOR GREATER PHILLY.
..GREAT LAKES
DAYS 1-3...
AFOREMENTIONED LOW PRESSURE SYSTEM STALLING OVER LAKE SUPERIOR
TODAY EJECTS SOUTHEAST TONIGHT WITH A REINFORCING SHORTWAVE TROUGH
PASSAGE ON MONDAY. SUBTERRANEAN DGZ UNDER THE LOW TODAY MAKES FOR
COARSE/LOW SLR SNOW, BUT SOME WARMING THIS EVENING BRINGS BACK THE
DENDRITES AND 20:1 SLRS TO THE U.P.
DAY 1 PWPF FOR >6" ARE 40-80% OVER NWLY FLOW SNOW BELTS IN THE
EASTERN U.P. AND EAST OF GRAND TRAVERSE BAY. WLY FLOW SNOW BELTS
EAST OF LAKES ERIE/ONTARIO RESULT IN DAY 1 PWPF >6" OF 30-50% EAST
OF CLEVELAND TO THE CHAUTAUQUA RIDGE AND OVER 80% FOR THE TUG HILL
WHERE SINGLE BANDING LES SETS UP THIS EVENING. LULL EXPECTED
FOR SUNDAY NIGHT AS LOW LEVEL RIDGING SHIFTS EAST OF THE LAKES. BUT
THEN SHORTWAVE CROSSES MONDAY WITH A DECENT, BUT TRANSIENT SWATH OF
LAKE ENHANCED SNOW. LIGHT TO LOCALLY MODERATE SYNOPTICALLY DRIVEN
SNOW ACROSS THE GREAT LAKES REGION MONDAY WITH MORE SINGLE BANDING
IN WESTERLY FLOW OVER LAKE ONTARIO INTO THE TUG HILL WHERE DAY 3
PWPF FOR >6" IS OVER 80%.
..PACIFIC NORTHWEST
DAYS 2/3...
POTENT ATMOSPHERIC RIVER ARRIVES MONDAY MORNING TO WESTERN WA/OR
WITH SNOW LEVELS SKYROCKETING UP TO 9000FT OVER THE CASCADES. A
SHORTWAVE TROUGH PASSAGE OVER WA LATE MONDAY BRINGS SNOW LEVELS ON
THE NORTH CASCADES DOWN TO 5000FT, REACHING 4000FT ON TUESDAY.
LOWER PRECIP RATES ARE EXPECTED BEHIND THE TROUGH PASSAGE, BUT
MODERATE SNOW BRINGS DAY 3 PWPF FOR >6" IN THE 40-60% RANGE IN THE
HIGH NORTHERN WA CASCADES.
THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.
JACKSON
..EXTREME COLD KEY MESSAGES ARE IN EFFECT AND LINKED BELOW
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_1.PNG
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