519
FOUS11 KWBC 201940
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 PM EST FRI FEB 20 2026
VALID 00Z SAT FEB 21 2026 - 00Z TUE FEB 24 2026
..PACIFIC NORTHWEST
DAYS 1-3...
CLOSED MID-LEVEL LOW WITH 500MB HEIGHTS BELOW THE 1ST PERCENTILE
ACCORDING TO NAEFS WILL SPIN SLOWLY OFF THE PACIFIC COAST THROUGH
THE WEEKEND. THIS POTENT LOW WILL SHED SPOKES OF VORTICITY
NORTHEAST WITHIN PERSISTENT WAA, LIFTING MOISTURE AND ASCENT
ONSHORE THE PACIFIC NORTHWEST. AT THE SAME TIME, AN INTENSIFYING
UPPER JET STREAK WILL BEGIN TO PIVOT NORTHEAST, AND WHERE IT LAYS
ABOVE THE MID-LEVEL WAA, AN IMPRESSIVE IVT PLUME (ATMOSPHERIC RIVER
OR AR) WILL SHIFT TOWARDS WA/OR WITH A HIGHER THAN 60% CHANCE OF
IVT EXCEEDING 500 KG/M/S. WHILE THIS EVOLUTION WILL DRIVE SNOW
LEVELS UPWARD FROM AROUND 4000 FT TO 6000 FT, KEEPING THE HEAVIEST
SNOW ABOVE MOST OF THE AREA PASSES, IT WILL RESULT IN HEAVY
SNOWFALL IN MUCH OF THE MOUNTAINOUS TERRAIN FROM THE
SHASTA/SISKIYOU REGION OF CA NORTHWARD ALONG THE CASCADES, INTO THE
OLYMPICS, AND EVENTUALLY REACHING THE FAR NORTHERN ROCKIES. THE
HEAVIEST SNOWFALL IS EXPECTED IN THE SHASTA/SISKIYOU REGION WHERE
3-DAY WPC PROBABILITIES FOR MORE THAN 12 INCHES ARE ABOVE 90%, WITH
1-3 FEET POSSIBLE IN THE HIGHEST ELEVATIONS. FARTHER NORTH, WPC
PROBABILITIES REACH ABOVE 70% FOR THE WA CASCADES AND OLYMPICS,
WITH THE HEAVIEST SNOWFALL LIKELY OCCURRING IN TWO ROUNDS: SATURDAY
AFTERNOON, AND AGAIN MONDAY MORNING.
..GREAT LAKES
DAYS 1-3...
TWO DISTINCT IMPULSES WILL BRING ROUNDS OF HEAVY SNOW TO PORTIONS OF
THE GREAT LAKES THROUGH THIS WEEKEND.
FOR TONIGHT INTO SATURDAY, A SURFACE LOW PRESSURE MOVING SLOWLY
EASTWARD FROM MICHIGAN INTO THE NORTHEAST WILL FILL THROUGH THE DAY,
LEAVING A LINGERING INVERTED TROUGH ORIENTED SE TO NW ACROSS THE
U.P. OF MICHIGAN. PERSISTENT LOW-LEVEL CONVERGENCE ALONG THIS
INVERTED TROUGH COMBINED WITH STEEPENED LAPSE RATES ALOFT BENEATH A
BROAD MID-LEVEL TROUGH WILL PROMOTE CONTINUED FAVORABLE ASCENT FOR A
NARROW CORRIDOR OF HEAVY SNOWFALL WITH SNOWFALL RATES ABOVE 1"/HR
POSSIBLE (30-50% CHANCE). THIS WILL BE A NARROW AXIS FOCUSED ACROSS
THE U.P., WEAKENING LATE D1, AND WPC PROBABILITIES INDICATE A HIGH
CHANCE (>70%) FOR MORE THAN 6 INCHES ACROSS THE KEWEENAW PENINSULA
AND THE HURON MOUNTAINS, WITH LOCALLY MORE THAN 12" POSSIBLE.
THIS TROUGH WEAKENS EARLY D2, BUT AS THAT OCCURS A MORE PRONOUNCED
SHORTWAVE TROUGH WILL DIG OUT OF CANADA ACROSS THE UPPER MIDWEST AND
INTO THE OHIO/TENNESSEE VALLEYS. WHILE SYNOPTIC ASCENT ACROSS THE
GREAT LAKES WILL BE MODEST DURING THIS EVOLUTION, THE FOLLOWING COLD
AIR ADVECTION (CAA) WILL CREATE AN ENVIRONMENT FAVORABLE FOR LAKE
EFFECT SNOW (LES) DESPITE ABUNDANT ICE COVER OVER THE LAKES. THE
HEAVIEST LES D2 IS EXPECTED ACROSS THE WESTERN U.P. AND WESTERN L.P.
WHERE N/NW FLOW SUPPORTS WPC PROBABILITIES AS HIGH AS 30% FOR 4+
INCHES OF SNOW. THEN DURING D3, CAA WILL EXPAND EASTWARD BEHIND A
LOW PRESSURE OFF THE ATLANTIC COAST, PRODUCING MODERATE BANDS OF LES
INTO NW IN AND ALONG THE CHAUTAUQUA RIDGE WHERE WPC PROBABILITIES
INDICATE A LOW RISK (10-30%) FOR 4+ INCHES OF SNOWFALL.
..NORTHEAST
DAY 1...
SURFACE LOW PRESSURE WEAKENING OVER MICHIGAN WILL EXTEND A WARM
FRONT/OCCLUDED FRONT EASTWARD INTO NEW ENGLAND, ALONG WHICH A
SECONDARY LOW PRESSURE WILL DEVELOP EAST OF MASSACHUSETTS. ALONG
THIS BOUNDARY, WAA DOWNSTREAM OF A MID-LEVEL SHORTWAVE TROUGH
EJECTING EASTWARD, WILL EXPAND PRECIPITATION NORTHWARD AS A REGION
OF HEAVY SNOW AND MIXED RAIN/SNOW/FREEZING RAIN. AS THE ACCOMPANYING
WARM NOSE PUSHES NORTHEAST, PRECIPITATION WILL BEGIN AS HEAVY SNOW
WITH SNOWFALL RATES ABOVE 1"/HR LIKELY (60-80% CHANCE), ESPECIALLY
ACROSS THE ADIRONDACKS, GREENS, AND WHITES WHERE ELEVATION WILL
SUPPORT MORE SNOW. THIS HEAVY SNOW WILL PIVOT EASTWARD THROUGH
TONIGHT, EXITING THE MAINE COAST BEFORE 12Z SATURDAY. HOWEVER, AS
THE SURFACE LOW OFFSHORE DEEPENS AND MOVES AWAY, POST-LOW CAA IN ITS
WAKE WILL ALLOW LIGHT SNOW (WITH HIGHER SLRS DUE TO A COLDER
AIRMASS) TO CONTINUE MUCH OF SATURDAY BEFORE ENDING SATURDAY NIGHT.
ADDITIONAL ACCUMULATIONS AFTER 12Z SATURDAY ARE EXPECTED TO BE
MINIMAL, SO MOST OF THE SNOWFALL, FOR WHICH WPC PROBABILITIES
SUGGEST HAS A HIGH RISK (>70% CHANCE) OF EXCEEDING 4" IN THE HIGHER
ELEVATIONS OF CENTRAL NEW ENGLAND (MODERATE RISK ELSEWHERE FROM
UPSTATE NY THROUGH SW COASTAL ME), WILL OCCUR BEFORE DAYBREAK
SATURDAY.
SOUTH OF THIS HEAVY SNOW AREA, AN AXIS OF LIGHT FREEZING RAIN IS
LIKELY AS P-TYPE TRANSITION OCCURS WITHIN THE WAA REGIME. TOTAL ICE
ACCUMULATION SHOULD BE LIGHT, BUT STILL IMPACTFUL, AS WPC
PROBABILITIES SUGGEST A 50-90% CHANCE OF AT LEAST 0.01" OF ICE FROM
THE CATSKILLS AND INTO THE BERKSHIRES, LITCHFIELD HILLS, AND
SOUTHERN WORCESTER HILLS.
..CENTRAL APPALACHIANS AND MID-ATLANTIC
DAY 3...
*** NOR'EASTER DEVELOPS OFF MID-ATLANTIC COAST SUNDAY WITH IMPACTS
IN THE NORTHEAST THROUGH MONDAY ***
COMPLEX PHASING EVOLUTION BETWEEN A STRONG N/S SHORTWAVE AND S/S
DISTURBANCE MIGRATING EAST OUT OF THE ROCKIES WILL GENERATE A
SIGNIFICANT SLP MATURATION ALONG THE ATLANTIC SEABOARD WITH
APPRECIABLE IMPACTS POISED FOR A LARGE PORTION OF THE MID-ATLANTIC
AND NORTHEAST. TRENDS THE LAST 24HRS HAVE FAVORED A CLEANER PHASE
SCENARIO WITH THE 500MB HEIGHT PATTERN AMPLIFYING ONCE EAST OF THE
MISSISSIPPI, NEGATIVELY TILTING AS THE PATTERN EVOLVES DOWNSTREAM
INTO THE OHIO VALLEY AND EAST COAST. MODEL DISCREPANCIES ARE
BEGINNING TO SHRINK WITH THE MAJORITY OF ENSEMBLE MEMBERS NOW
SHOWING A MORE "TUCKED" SLP SOLUTION, ALBEIT LOCATION OF PRIMARY
COASTAL IS STILL BEING WORKED OUT AS IT REACHES THE LATITUDE OF
MD/DE WHICH WOULD IMPLY FAIRLY ROBUST IMPLICATIONS IN TERMS OF THE
POSITIONING OF THE CCB DEVELOPMENT AND ACCOMPANYING NORLUN
(INVERTED) TROUGH AXIS THAT WILL LIKELY DEVELOP DUE TO THE PHASING
PATTERN AND 500MB ULL PROGRESSION ACROSS THE CENTRAL AND SOUTHERN
MID ATLANTIC.
SENSIBLE WEATHER PATTERN WILL LIKELY BEGIN EARLY SUNDAY MORNING
WITH A LIGHT PRECIP FIELD ENTERING THE CENTRAL AND SOUTHERN MID
ATLANTIC, ENCROACHING A RELATIVELY BENIGN ANTECEDENT AIRMASS WITH
THE LOWER PBL LIKELY TO BE MARGINAL OR JUST TOO WARM FOR SNOWFALL
UNTIL YOU GET FURTHER NORTH CLOSER TO THE MASON DIXON AND NORTHWEST
OF THE FALL LINE IN THE PIEDMONT WHERE WETBULB TEMPS ARE FORECAST
TO BE NEAR FREEZING AT PRECIP ONSET. FURTHER SOUTH OFF THE
CAROLINA COAST, SURFACE CYCLOGENESIS WILL MATERIALIZE WITHIN A
STRENGTHENING DIFFLUENT AXIS AHEAD OF THE AMPLIFYING MEAN TROUGH,
AND WITHIN THE LER OF A STRONG UPPER JET ROUNDING THE TROUGH BASE
ACROSS THE SOUTHERN MID ATLANTIC. AS THIS EVOLUTION MATERIALIZES
OVER THE COURSE OF SUNDAY, EXPECTATION IS FOR THE PRECIP FIELD TO
BLOSSOM WITH HEIGHT FALLS ENCROACHING THE REGION ALLOWING FOR
REPUTABLE DIABATIC COOLING TO AID IN LOWER PBL TEMPERATURES TO
COOL, THUS CHANGING THE PRIMARY HYDROMETEORS FROM A MIXTURE OF
LIQUID/SOLID, TO ALL SOLID, IMPLYING A SHIFT TO SNOWFALL WITH A
FAVORED COLLAPSE OF THE RAIN/SNOW LINE FROM NORTHWEST TO SOUTHEAST.
AS THIS OCCURS, EXPECTATION IS FOR RATES TO BEGIN PICKING UP UNDER
THE INFLUENCE OF AN ULL PASSAGE ACROSS VA LEADING TO HEIGHTENED
ASCENT NORTH OF THE CLOSED 500MB PROGRESSION WITH INCREASING
COVERAGE OF BANDING STRUCTURES AS THE DYNAMICAL PROCESSES BEGIN TO
MATURE. CROSS- SECTIONS FROM MOST OF THE NUMERICAL SUITE INDICATE
APPRECIABLE OMEGA ACROSS THE CENTRAL MID ATLANTIC OVER TO THE
DELMARVA AND POINTS NORTHEAST AS THE SYSTEM CONTINUES TO EVOLVE AND
THE CYCLONE DEEPENS RAPIDLY OFF THE MID ATLANTIC COAST.
AREAS FURTHEST WEST FROM THE PRIMARY SURFACE LOW WILL, AT THE VERY
LEAST BE UNDER A THREAT FROM A MATURING NORLUN TROUGH THAT IS
PRETTY WELL-DEFINED WITHIN SEVERAL OF THE MAIN NWP OUTPUTS,
INCLUDING THE GLOBAL DETERMINISTIC. THIS AREA WILL BE A RELATIVELY
NARROW CORRIDOR OF HEAVY PRECIP WITH SIGNIFICANT ASCENT ALLOWING
FOR A BAND OF HEAVY SNOW TO DEVELOP AND SLOWLY PROGRESS EAST-
NORTHEAST THROUGH THE STORMS LIFE CYCLE. SOME GUIDANCE GOES AS FAR
AS A FULL "CAPTURE" AT THE MID-LEVELS WHICH ALLOWS FOR THE SURFACE
LOW OFF THE ATLANTIC COAST TO SLOW CONSIDERABLY AND TUCK CLOSER TO
THE COAST ALLOWING FOR A MORE PRONOUNCED COASTAL ENHANCEMENT TO BE
THROWN BACK FURTHER WEST WITH A ROBUST QPF DISTRIBUTION WITHIN A
DEFINED CCB AXIS THAT WILL DEVELOP TO THE WEST OF THE SURFACE
REFLECTION. THESE OUTPUTS ARE GENERATING THE MORE SIGNIFICANT
SNOWFALL ACCUMULATIONS ACROSS THE MID ATLANTIC TO SOUTHERN NEW
ENGLAND IN NWP OUTPUT. THAT IS ONLY ONE POTENTIAL OUTCOME HOWEVER,
AS CURRENT CLUSTER ANALYSIS INDICATES TWO OTHER VIABLE SCENARIOS
THAT STILL DELIVER SOLID SNOWFALL TOTALS, BUT NOT AS PRONOUNCED DUE
TO A LOWER INFLUENCE DIRECTLY FROM THE COASTAL. INVERTED TROUGH
AXIS IS MOST LIKELY TO BENEFIT AREAS WEST OF THE CHESAPEAKE BAY UP
INTO PA WITH THE COASTAL IMPACTS LIKELY TO BE FELT FROM COASTAL
DELMARVA UP THROUGH COASTAL NJ, EASTERN LI, AND SOUTHEAST NEW
ENGLAND. THESE AREAS HAVE SEEN AN APPRECIABLE UPTICK IN THE PROB
FIELDS FOR ALL REPUTABLE TOTALS, BUT ESPECIALLY >6", WHICH IS UP TO
40-80% ACROSS THE AFOREMENTIONED AREAS. THE AREAS WITH MORE
QUESTION MARKS ARE FURTHER WEST AND NORTHWEST AWAY FROM THE COASTAL
AREAS JUST DUE TO POTENTIALLY MISSING THE COASTAL ENHANCEMENT AND
LOSING SOME OF THE PRECIP TO THE MARGINAL AIRMASS PRESENCE. THAT
SAID, THIS SETUP IS FORECAST TO BE VERY DYNAMIC WITH APPRECIABLE
ASCENT WITHIN THE COLUMN WITH A FAVORABLE 850-500MB EVOLUTION
CAPABLE OF PRODUCING SNOWFALL RATES >1"/HR FOR HOURS, EVEN WITHIN
THAT NORLUN TROUGH AXIS THAT WILL DEVELOP.
THE GREATER CONFIDENCE FOR >6" IS DUE TO UPSLOPE SNOW ON THE
CENTRAL APPALACHIANS IN NW FLOW ON THE BACK SIDE OF THE SYSTEM
SUNDAY NIGHT. GREAT LAKES MOISTURE ENCOUNTERS THE TOPOGRAPHICAL
LIFT WITH DAY 3 SNOW PROBS FOR >6" 60-90% ABOVE ABOUT 1500FT TO
THE ALLEGHENY FRONT IN WV AND FAR WESTERN MD. MEDIUM CONFIDENCE
(40-70%) FOR >4" EXISTS FOR AREAS OF CENTRAL MD TO POINTS
NORTHEAST INTO EASTERN PA/WESTERN NJ/SOUTHERN NY/CT WITH THE BEST
CHANCE FOR AREAS >600FT ELEVATION. METRO AREAS WILL HAVE THE USUAL
UHI CONCERNS, HOWEVER STRONG RATES AND DIABATIC COOLING COULD VERY
WELL TIP THE SCALES HERE AND ENTICE HEAVY SNOWFALL WITH REPUTABLE
TOTALS WORTHY OF A HIGHER-END ADVISORY OR EVEN LOW-END WARNING WITH
THE BEST ACCUMULATION TIME FRAME TO OCCUR EARLY SUNDAY EVENING AND
OVERNIGHT WHEN DIURNAL ELEMENTS HAVE CONSIDERABLY LESS IMPACT.
POINT REMAINS THAT A POWERFUL SURFACE CYCLONE AND HIGHLY DYNAMIC
SETUP WILL IMPACT THE MID ATLANTIC THROUGH THE NORTHEAST SUNDAY AND
MONDAY WITH A POTENTIAL FOR AT LEAST MODERATE IMPACTS TO AFFECT
THE URBAN CORRIDOR FROM DC TO BOSTON, SURROUNDING SUBURBS TO THE
COAST.
WEISS/KLEEBAUER
...WINTER STORM KEY MESSAGES ARE IN EFFECT. PLEASE SEE CURRENT
KEY MESSAGES BELOW...
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_1.PNG
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