418
FOUS11 KWBC 162015
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 PM EST SUN FEB 16 2025
VALID 12Z SUN FEB 16 2025 - 12Z WED FEB 19 2025
..GREAT LAKES/NORTHEAST
DAYS 1-2...
A DYNAMIC WINTER STORM IS UNFOLDING TODAY WITH HEAVY SNOW ACROSS
NORTHERN MAINE, WHILE A PROTRUDING WARM NOSE OF >0C AIR AT LOW
LEVELS CAUSES PRECIPITATION TO FALL IN THE FORM OF SLEET AND/OR
FREEZING RAIN FROM CENTRAL MAINE AND THE NORTHERN APPALACHIANS TO
THE MAINE COAST. WPC'S SNOWBAND PROBABILITY TRACKER SHOWS THE HREF
GUIDANCE SUITE HAS MEMBERS THAT ARE PRODUCING AS MUCH AS 1-2"/HR
SNOWFALL RATES ACROSS NORTHERN MAINE THROUGH THIS EVENING. HEAVY
SNOW IS EXPECTED IN PARTS OF NY'S NORTH COUNTRY THIS EVENING, AND
ON THE WESTERN FLANK OF THE STORM AS IT TRACKS INTO MAINE TONIGHT.
WPC PROBABILITIES SHOW HIGH CHANCES (>70%) FOR SNOWFALL >8" IN THE
NORTH WOODS, CENTRAL AROOSTOOK, AND ST. JOHN VALLEY, WITH THE
LATTER OF THE THREE HAVING HIGH CHANCES (>70%) FOR OVER A FOOT OF
SNOW. A COUPLE ADDITIONAL INCHES OF SNOW ARE POSSIBLE IN THE
ADIRONDACKS AND THE REST OF VT AS THE STORM PULLS AWAY. MEANWHILE,
SOUNDINGS WILL BE MORE SUPPORTIVE OF FREEZING RAIN AND SLEET
FARTHER SOUTH WITH ANOTHER TENTH TO A QUARTER INCH OF ICE EXPECTED
FROM SOUTHERN AND CENTRAL NH/VT ON EAST THROUGH THE SOUTHERN TIER
OF MAINE. STRONG WIND GUSTS TOPPING 50 MPH COULD ADD FURTHER STRESS
TO TREES AND POWER LINES WITH HEAVY/WET SNOW OR ICE, KEEPING THE
POTENTIAL FOR ADDITIONAL POWER OUTAGES AND TREE DAMAGE AS A
POTENTIAL IMPACT THROUGH MONDAY MORNING.
ON THE BACKSIDE OF THE WINTER STORM, MUCH COLDER AIR RACES ACROSS
THE GREAT LAKES AND INTO THE CENTRAL APPALACHIANS, GIVING RISE TO
LAKE EFFECT SNOW BANDS AND UPSLOPE SNOW IN THESE REGIONS. FOR
THE POTOMAC HIGHLANDS OF EASTERN WV ON NORTH TO THE LAUREL
HIGHLANDS, UPSLOPE FLOW WILL GENERATE LOCALLY HEAVY SNOW TOTALS
WITH WPC PROBABILITIES SPORTING MODERATE-TO-HIGH CHANCES (50-70%)
FOR >6" IN THESE MOUNTAIN RANGES. SNOW WILL TAPER OFF IN THE
CENTRAL APPALACHIANS BY MIDDAY MONDAY, WHILE THE LAKE EFFECT SNOW
MACHINE LOOKS TO KEEP PRODUCING BANDS OF HEAVY SNOW THROUGH TUESDAY
AS AN UPPER LOW HEADS FOR THE EASTERN CANADIAN MARITIME AND AN
ELONGATED 500MB TROUGH AXIS MOVES IN OVERHEAD. LOW LEVEL FLOW
BACKS FROM NW TO WNW AND FAVOR THE TYPICAL LAKE BELTS, BUT MOST
NOTABLY OVER THE EASTERN U.P. OF MICHIGAN AND SOUTHEAST OF LAKE
ONTARIO. WPC PROBABILITIES FOR AT LEAST 8" OF SNOW OVER THE NEXT
FEW DAYS ARE HIGH (>70%) AND ARE MODERATE-TO-HIGH (50-70%) FOR 18
INCHES OF SNOW DOWNWIND OF LAKE ONTARIO.
..PACIFIC NORTHWEST/ROCKIES/NORTHERN HIGH PLAINS
DAYS 1-3...
AN ACTIVE PACIFIC JET WILL DIRECT A STORM SYSTEM AND ITS ASSOCIATED
IVT TO THE SOUTH OF THE STORM INTO THE NORTHWESTERN U.S. THROUGH
MONDAY, FOLLOWED BY ANOTHER SYSTEM BY TUESDAY INTO WEDNESDAY. SNOW
LEVELS WILL DIP JUST BELOW PASS LEVEL AND OSCILLATE THERE THROUGH
MONDAY NIGHT. EAST OF THE CONTINENTAL DIVIDE A VERY COLD AIR MASS
WILL BE IN PLACE THANKS TO HIGH PRESSURE OVER CANADA THAT PUSHES
SOUTHWARD THROUGH THE PLAINS, SETTING UP UPSLOPE FLOW INTO WESTERN
MT. FOR THE FIRST SYSTEM, SUN-MON (THOUGH INTO TUE OVER WY), THE
HIGHEST SNOW TOTALS WILL BE OVER THE CASCADES EASTWARD INTO THE
CENTRAL IDAHO RANGES, WESTERN MT/WY AND INTO NORTHERN CO/SOUTHERN
WY. SEVERAL FEET OF SNOW ARE LIKELY IN THE HIGHER TERRAIN WITH ONLY
A BRIEF BREAK BETWEEN SYSTEMS. IVT VALUES EXCEEDING THE 90TH
PERCENTILE WILL MOVE THROUGH THE REGION TODAY, BUT THEN DROP AFTER
TONIGHT AS THE JET FLATTENS OUT. NEVERTHELESS, THE NEARLY
CONTINUOUS TERRAIN- ENHANCED SNOW WILL ACCUMULATE WELL OVER 1-2 FT
WITH WPC PROBS > 70% IN THE MOUNTAINS. SNOW WILL BE FAIRLY HEAVY
OVER WESTERN-CENTRAL MT ON THE UPSLOPE SIDE AS WELL, WHERE WPC
PROBS FOR AT LEAST 8" OF SNOW ARE >50% AROUND BILLINGS UP TO GREAT
FALLS.
THE NEXT SYSTEM WILL ENTER THE PACIFIC NORTHWEST STARTING TUESDAY
NIGHT WITH SOME PERIODS OF SNOW FOR THE CASCADES. SNOW WILL THEN
EXTEND INTO THE NORTHERN ROCKIES THROUGHOUT THE DAY ON WEDNESDAY.
WPC PROBABILITIES SHOWS MODERATE-TO-HIGH CHANCES (50-70%) FOR >6"
OF SNOWFALL FOR THE CASCADES, BLUE, AND SAWTOOTH MOUNTAIN RANGES.
..CENTRAL PLAINS/MID-MS VALLEY/MID-SOUTH
DAYS 1-3...
THE ANOMALOUS IVT RESPONSIBLE FOR PERIODS OF HEAVY SNOW IN THE
ROCKIES WILL ACCOMPANY A PERIOD OF 700MB WAA OVER THE CENTRAL
PLAINS. THE COMBINATION OF 700MB FGEN AND AN ACCELERATING 250MB
JET ALOFT WILL SUPPORT A STRIPE OF MODERATE SNOW FROM THE BLACK
HILLS ON SOUTH AND EATS THROUGH NE AND INTO THE LOWER MISSOURI
RIVER VALLEY TONIGHT AND INTO MONDAY. THIS BAND EVENTUALLY WEAKENS
TO WHERE MAINLY LIGHT SNOW IS EXPECTED IN THESE AREAS THROUGH
MONDAY AFTERNOON. BY MONDAY NIGHT, THE STRONGER 500MB SHORTWAVE
TROUGH TRACKING ACROSS THE CENTRAL ROCKIES WILL GRADUALLY DEEPEN
WHILE UPPER-LEVEL DIFFLUENCE INCREASES AT THE NOSE OF A 250MB JET
STREAK ROUNDING THE BASE OF THE CENTRAL ROCKIES TROUGH. BY EARLY
TUESDAY MORNING, THE AFOREMENTIONED JET STREAK WILL CO-LOCATE ITS
DIVERGENT LEFT-EXIT REGION WITH THE DIVERGENT RIGHT-ENTRANCE
REGION OF A STRENGTHENING JET STREAK OVER THE EASTERN U.S.. AS
SOUTHERLY AND MOIST 850MB WINDS INCREASE OVER TEXAS AND LOW-LEVEL
WAA RESULTS IN 850MB FGEN FROM THE OK/TX PANHANDLES TO AS FAR EAST
AS THE OZARKS AND OUACHITA MOUNTAINS, PERIODS OF HEAVY SNOW WILL
ENVELOPE THESE REGIONS WITH DETERIORATING TRAVEL CONDITIONS
THROUGHOUT THE DAY.
THERE ARE STILL SOME DIFFERENT SCENARIOS ON GUIDANCE AS TO WHERE
AND HOW LONG THE HEAVIEST BANDS OF SNOW TAKE SHAPE. WPC
PROBABILITIES ARE KEYING IN ON SOUTHEAST KS, SOUTHERN MO, AND AS
FAR EAST AS THE MISSISSIPPI RIVER BORDERING SOUTHEAST MO AND
WESTERN KY AS MOST LIKELY TO WITNESS HEAVY SNOW WHERE THERE ARE
HIGH CHANCES (>70%) FOR SNOWFALL AMOUNTS TOPPING 6". IN FACT, THERE
ARE LOW-TO-MODERATE CHANCES (30-50%) IN SOUTHERN MO FOR >12" OF
SNOWFALL. FARTHER SOUTH ACROSS NORTHERN OK, NORTHERN AR, AND
NORTHWEST TN, A DISRUPTIVE BLEND OF SNOW AND ICE WOULD MAKE FOR
TREACHEROUS TRAVEL CONDITIONS TUESDAY AND CONTINUING INTO TUESDAY
NIGHT. AS THE STORM TRACKS EAST INTO THE MID-SOUTH ON WEDNESDAY,
HEAVY SNOW WILL BLANKET AREAS FROM THE OH-MS RIVER CONFLUENCE ON
EAST INTO THE OHIO VALLEY. WPC PROBABILITIES DO DEPICT MODERATE
CHANCES (40-60%) FOR SNOWFALL TOTALS >4" IN THESE AREAS. FOR ICE
ACCUMULATIONS, THE OUACHITA MOUNTAINS SPORT LOW-TO-MODERATE CHANCES
(30-50%) FOR ICE ACCUMULATIONS >0.1" THROUGH WEDNESDAY MORNING.
WPC'S WSSI-P SHOWS LOW-TO-MODERATE CHANCES (30-50%) FOR MAJOR
IMPACTS (DANGEROUS OR IMPOSSIBLE TRAVEL CONDITIONS; WIDESPREAD
CLOSURES AND DISRUPTIONS) FOR NORTHEAST OK, SOUTHEAST KS, SOUTHERN
MO, AND FAR NORTHERN AR. AS HIGH AS 60% CHANCES EXIST FOR MODERATE
IMPACTS (HAZARDOUS DRIVING CONDITIONS; SOME CLOSURES AND
DISRUPTIONS) STRETCH AS FAR WEST AS WICHITA AND THE I-35 CORRIDOR
ON EAST TO NORTHERN TN AND WESTERN KY.
..CENTRAL APPALACHIANS/MID-ATLANTIC
DAY 3...
AS THE UPPER-LEVEL TROUGH DRIVING THE MID-SOUTH STORM SYSTEM TRACKS
EAST ON WEDNESDAY, MODEST PVA ALOFT COMBINED WITH 850-700MB WAA
WILL DIRECT THE SHIELD OF HEAVY SNOW IN THE MID-SOUTH TOWARDS THE
APPALACHIANS AND MID-ATLANTIC. WHAT GUIDANCE LARGELY AGREES UPON IS
THE SOUTHERN STREAM STORM SYSTEM TRACKING ENE TOWARDS THE SOUTHEAST
COAST WEDNESDAY AFTERNOON AND STEADILY STRENGTHENING BENEATH THE
DIVERGENT RIGHT-ENTRANCE REGION OF A STRENGTHENING 140KT 250MB JET
STREAK TO THE NORTH. THERE IS AN ANOMALOUS IVT TOPPING 500 KG/M/S
OVER THE SOUTHEAST THAT WILL HELP DIRECT PLENTY OF MOISTURE INTO
THE SOUTHERN MID-ATLANTIC. AS 850-700MB FGEN OCCURS OVER SOUTHERN
VA, BANDS OF HEAVY SNOW SHOULD TAKE SHAPE AND LEAD TO HAZARDOUS
TRAVEL CONDITIONS FROM SOUTHWEST VA AND THE CENTRAL APPALACHIANS
OF WV AND WESTERN VA TO THE VA TIDEWATER WEDNESDAY AFTERNOON.
PROBABILISTIC GUIDANCE IS SUGGESTING AN AREA FROM EASTERN KY AND
THE WV/WESTERN VA APPALACHIANS TO THE DELMARVA PENINSULA AS HAVING
THE BEST ODDS OF SEEING HEAVY SNOW. WPC PROBABILITIES SHOW A
GROWING AREA OF MODERATE-TO-HIGH CHANCE PROBABILITIES (50-70%) FOR
SNOWFALL >4" IN SOUTHWEST VA THROUGH WEDNESDAY EVENING, WITH HEAVY
SNOW SPREADING ACROSS SOUTHERN VA AND THE DELMARVA PENINSULA BY
WEDNESDAY EVENING. WITH THE STORM ALSO DEEPENING AS IT REACHES THE
COAST WEDNESDAY NIGHT, BLOWING SNOW AND HEAVY SNOWFALL RATES OF
1-2"/HR WOULD CAUSE NEAR WHITEOUT CONDITIONS, ESPECIALLY FOR THE
DELMARVA PENINSULA. THERE IS ALSO THE CONCERN FOR SIGNIFICANT ICING
AS WPC PROBABILITIES SHOW MODERATE-TO-HIGH CHANCES (50-70%) FOR
>0.01" OF ICE OVER CENTRAL NC AND NORTH-CENTRAL SC. THESE AREAS
WOULD BE MOST AT RISK FOR TREACHEROUS DRIVING CONDITIONS ON
WEDNESDAY.
HOWEVER, 500MB SKEWNESS PLOTS CONTINUE TO SHOW SOME SUBTLE
DIFFERENCE IN THE DEPTH/STRENGTH OF THE LARGE UPPER LOW OVER THE
MIDWEST AND HOW IT INTERACTS WITH THE LEAD SHORTWAVE TROUGH IN THE
SOUTHEAST. FARTHER SOUTHEAST, WHILE NOT AS PRONOUNCED THERE ARE
ALSO LINGERING DISCREPANCIES IN THE DEPTH/SPEED OF THE LEAD TROUGH
IN THE SOUTHEAST AS WELL. WHILE MOST ENSEMBLE GUIDANCE HAS STARTED
TO COME INTO FOCUS WITH SOUTHERN VA AND THE DELMARVA PENINSULA
BEING MOST FAVORED FOR HEAVY SNOW, A DEEPER/MORE PHASED UPPER-
LEVEL PATTERN WOULD ALLOW FOR HEAVY SNOW TO CREEP NORTHWARD UP
I-95 AND GET CLOSER TO THE MAJOR METRO CENTERS OF WASHINGTON D.C. AND
BALTIMORE. THERE ARE ALSO SOME SOLUTIONS THAT SHOW THE LEAD
SHORTWAVE COULD BE FLATTER AS WELL, AND MAKE NORTHERN NC AND FAR
SOUTHEAST VA THE FOCUS FOR HEAVY SNOW. RESIDENTS IN THE MID-
ATLANTIC SHOULD KEEP A CLOSE EYE ON THE FORECAST AS ANY SUBTLE
ADJUSTMENT IN SPEED/TIMING/PHASING OF THESE ATMOSPHERIC VARIABLES
COULD MEAN 50-100 MILE SHIFTS IN WHERE THE HEAVY SNOWFALL AXIS SETS
UP.
MULLINAX
...WINTER STORM KEY MESSAGES ARE IN EFFECT. PLEASE SEE CURRENT
KEY MESSAGES BELOW...
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_1.PNG
HTTPS://WWW.WPC.NCEP.NOAA.GOV/KEY_MESSAGES/LATESTKEYMESSAGE_2.PNG
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