459
FOUS11 KWBC 301835
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EST FRI JAN 30 2026
VALID 00Z SAT JAN 31 2026 - 00Z TUE FEB 03 2026
..SOUTHERN APPALACHIANS, MID-ATLANTIC, & SOUTHERN NEW ENGLAND
DAYS 1-2...
...A MAJOR WINTER STORM IS EXPECTED TO PRODUCE HEAVY SNOWFALL AND
BLIZZARD CONDITIONS ACROSS THE SOUTHERN MID-ATLANTIC...
THE SYNOPTIC EVOLUTION CONTINUES TO SUPPORT A MAJOR WINTER STORM,
PRIMARILY FOCUSED OVER THE CAROLINAS, BUT QUESTIONS ABOUT THE
DETAILS CONTINUE.
THE EVENT BEGINS THIS EVENING, AS SNOW BREAKS OUT ACROSS THE
SOUTHERN APPALACHIANS OF NC/TN. THIS INITIAL DEVELOPMENT OF SNOW
WILL BE IN RESPONSE TO INCREASING SYNOPTIC ASCENT WITHIN STRONG
MID-LEVEL DIVERGENCE DOWNSTREAM OF A PIVOTING SHORTWAVE DIGGING OUT
OF THE GREAT LAKES. AS THIS SHORTWAVE DIVES SOUTHWARD OUT OF THE
GREAT LAKES, IT WILL RAPIDLY DEEPEN INTO AN IMPRESSIVE CLOSED LOW
BY 12Z SATURDAY OVER THE TENNESSEE VALLEY, AND THEN CONTINUE TO
DIVE SOUTHEAST, REACHING THE GA/SC COAST BY 00Z SUNDAY. THIS WILL
PRODUCE EXTREME ANOMALIES OF MORE THAN -5 SIGMA WITH RESPECT TO
500MB HEIGHTS ACCORDING TO NAEFS ACROSS THE SOUTHEAST/GULF COAST,
INDICATIVE OF HOW RARE AND EXTREME THIS SETUP WILL BE. AS THE UPPER
LOW DEEPENS AND DROPS SOUTHWARD, FORCING WILL INTENSIFY IN RESPONSE
TO NOT ONLY THE MID-LEVEL DIVERGENCE NOTED ABOVE, BUT ADDITIONAL
ROBUST HEIGHT FALLS, AND INCREASING JET-LEVEL DIFFLUENCE AS A
DOWNSTREAM SUBTROPICAL JET STREAKS STRENGTHENS ACROSS THE GULF AND
THEN BEGINS TO ARC POLEWARD ALONG THE SOUTHEAST COAST. THIS WILL
HELP GENERATE SURFACE CYCLOGENESIS ALONG THE COAST OF THE
CAROLINAS, WITH DUAL LOW-PRESSURE SYSTEMS PROGGED, EACH ONE
DEEPENING ALONG THE INTENSE BAROCLINIC GRADIENT POSITIONED OFFSHORE
OWING TO THE RECENT EXTREMELY COLD AIR BLANKETED ACROSS THE EASTERN
CONUS.
THE SECONDARY SURFACE LOW, WHICH IS LIKELY TO BE THE MORE INTENSE
FEATURE AS IT EXPLOSIVELY INTENSIFIES SATURDAY NIGHT INTO SUNDAY
(MAYBE REACHING INTO THE 960S OFFSHORE) IS PROGGED TO PIVOT MORE
EAST THAN NORTHEAST ALONG THE COAST, SO THE HEAVY PRECIPITATION
SHOULD BE GENERALLY CONFINED TO THE CAROLINAS, SOUTHERN VA, AND
MAYBE CAPE COD AS IT PULLS AWAY. WHILE THERE IS CONTINUED
UNCERTAINTY INTO THE EXACT AMOUNTS OF PRECIPITATION DUE TO DRY AIR
ALOFT AND INTENSE MESOSCALE ASCENT THAT WILL DRIVE BANDS OF HEAVY
SNOW, THERE IS HIGH CONFIDENCE IN THIS OVERALL SYNOPTIC EVOLUTION,
RESULTING IN HIGH CONFIDENCE IN THE MOST IMPACTED AREAS.
THE COLUMN WILL BE EXTREMELY COLD, SO OTHER THAN POSSIBLY SOME
LIGHT RAIN ALONG THE COAST TO START THE EVENT, THIS WILL BE AN
ALL-SNOW SCENARIO WITH ABOVE-CLIMO SLRS, A RARITY FOR THIS PART OF
THE COUNTRY. AS NOTED ABOVE, THE SNOW BEGINS ACROSS THE
APPALACHIANS FRIDAY EVENING AND THEN EXPAND RAPIDLY TO THE SOUTH
AND EAST AS THE UPPER LOW DIVES TOWARDS THE GULF AND LOW PRESSURE
DEVELOPMENT OCCURS OFFSHORE. THIS EXPANSION OF PRECIPITATION WILL
BE DRIVEN PRIMARILY BY INCREASING 850MB EASTERLY FLOW, TAPPING INTO
THE GROWING THETA-E RIDGE OFFSHORE, WITH THE RESULTANT WAA LEADING
TO THE EXPANDING SNOW SHIELD, SOME OF THIS WAA COULD BE INTENSE AS
REFLECTED BY STRENGTHENING 925-700MB FGEN, WELL ALIGNED INTO THE
DEEP DGZ (>70% CHANCE OF AT LEAST 100MB OF DGZ DEPTH ACCORDING TO
THE SREF). THIS WILL SUPPORT NOT ONLY EXPANDING SNOWFALL, BUT
INTENSIFYING SNOWFALL SUCH THAT BY 00Z/SUNDAY AT LEAST MODERATE
SNOWFALL RATES SHOULD ENCOMPASS NEARLY THE ENTIRETY OF THE
CAROLINAS AND INTO NORTHEAST GA AND SOUTHERN VA.
AFTER 00Z SUNDAY IS WHEN THE HEAVIEST SNOW AND MOST NOTABLE IMPACTS
ARE EXPECTED AS THE LOW OFFSHORE DEEPENS RAPIDLY. THIS WILL PIVOT
WINDS TO MORE N/NE ACROSS THE REGION, AND AS A DEFORMATION AXIS
PIVOTS WEST OF THE SURFACE LOW AND THE COLD CONVEYOR SETS UP ACROSS
THE ATLANTIC AND INTO THE EASTERN CAROLINAS, MORE INTENSE ASCENT
AND GREATER MOISTURE SHOULD RESULT IN EXTREME (FOR THIS REGION)
SNOW RATES. CROSS-SECTIONS INDICATE A BROAD REGION OF FAVORABLE
CONDITIONS FOR CSI, OR EVEN CI (THUNDERSNOW), AND THE HREF SNOW-
RATE PROBABILITIES PEAK ABOVE 50% FOR 1"/HR SUGGESTING AT LEAST A
POTENTIAL FOR 2"/HR WITHIN A PIVOTING BAND SOMEWHERE IN EASTERN NC
OR SC, AND THIS IS ADDITIONALLY SUPPORTED BY THE WPC PROTOTYPE
SNOWBAND TOOL. THESE HEAVY SNOW RATES WILL BE ACCOMPANIED BY
STRONG WINDS THAT MAY GUST 35-50 MPH, HIGHER AT THE COAST AND IN
THE MOUNTAINS, SUGGESTING NEAR BLIZZARD CONDITIONS IN MANY AREAS.
WHILE UNCERTAINTY REMAINS INTO HOW DRY AIR IN THE MID- LEVEL MAY
IMPACT SNOW AMOUNTS ON THE BROAD SCALE, LOCALLY VERY SIGNIFICANT
SNOWFALL ACCUMULATIONS ARE LIKELY, ESPECIALLY WITHIN THESE BANDS,
DURING D2. BY SUNDAY AFTERNOON THE LOW WILL PULL AWAY BRINGING AN
END TO THE SNOWFALL AND LEAVING JUST COLD WINDY CONDITIONS IN ITS
WAKE.
THE EXCEPTION WILL BE ACROSS FAR SOUTHEAST MASSACHUSETTS AND ONTO
CAPE COD AND THE ISLANDS WHERE, DESPITE A SUBTLE SOUTHEAST TREND IN
TODAY'S MODEL GUIDANCE, PERIODS OF MODERATE SNOW ARE STILL EXPECTED
DUE TO ONSHORE FLOW AND SUFFICIENT SYNOPTIC ASCENT INTO THE
MOISTENING COLUMN. A PERIOD OF MODERATE SNOWFALL IS LIKELY, WITH
SOME LOCAL ENHANCEMENT SOUTH OF BOSTON AND ON THE OUTER CAPE DUE TO
OCEAN INFLUENCES, SUNDAY AFTN/EVE.
WPC PROBABILITIES FOR THE EVENT ARE QUITE ROBUST FOR BOTH THE
APPALACHIANS AND EASTERN NORTH CAROLINA, WHERE THEY ARE ABOVE 50%
FOR 8+ INCHES, AND 30-50% FOR 12+ INCHES. THE GREATEST POTENTIAL
FOR MORE THAN 12 INCHES APPEARS TO BE EASTERN NC WHERE THE
DEFORMATION BAND MAY PIVOT, BUT A WIDESPREAD 4-8" SNOWFALL APPEARS
LIKELY FROM SOUTHERN VA THROUGH NORTHERN SC, WITH IMPACTFUL
ACCUMULATIONS EXPECTED IN AREAS LIKE RICHMOND, VA, CHARLOTTE AND
RALEIGH, NC, COLUMBIA, SC, AND EVEN INTO ATLANTA, GA. FARTHER
NORTHEAST, WPC PROBABILITIES ARE 30-50% FOR 4+ INCHES ACROSS THE
CAPE AND ISLANDS.
KEY MESSAGES ARE IN EFFECT FOR THIS STORM, AND ARE LINKED BELOW
(KEY MESSAGE #2).
..GREAT LAKES
DAY 1...
POTENT SHORTWAVE DIVING SOUTHWARD WITHIN BROAD CYCLONIC FLOW INTO
THE TENNESSEE VALLEY SATURDAY MORNING WILL RAPIDLY SHARPEN THE
EASTERN CONUS TROUGH LEAVING PRONOUNCED CAA ON NORTHERLY FLOW IN
ITS WAKE. THIS WILL RESULT IN CONTINUED LAKE EFFECT SNOW (LES),
ESPECIALLY IN THE FAVORED NORTH SNOW BELTS SOUTH OF LAKE ONTARIO
AND ESPECIALLY SOUTH OF LAKE MICHIGAN WHERE THE LONG FETCH OF THE
LAKE WILL BE MAXIMIZED TO PRODUCE A NARROW BAND OF HEAVY SNOWFALL.
ALTHOUGH THE LAKES ARE COOLING AND HAVE MUCH HIGHER ICE COVERAGE
THAN A WEEK OR TWO AGO, FRIGID 850MB TEMPERATURES MOVING OVERHEAD
WILL CREATE STRONG DELTA-TS TO SUPPORT SNOWFALL RATES THAT HAVE A
30-40% CHANCE (FROM THE HREF) OF EXCEEDING 1"/HR, GREATEST ACROSS
NW INDIANA. WHILE SOME LIGHT ACCUMULATIONS ARE LIKELY SOUTH OF LAKE
ONTARIO, WPC PROBABILITIES FOR 4+ INCHES ARE CONFINED TO NW IN
WHERE THEY REACH 30-50%.
..NORTHERN PLAINS THROUGH THE UPPER MIDWEST AND GREAT LAKES
DAYS 1-3...
A SHORTWAVE EMERGING FROM THE PACIFIC WILL CREST THE RIDGE OVER THE
PACIFIC NORTHWEST AND THEN DIVE SLOWLY SOUTHEAST INTO THE NORTHERN
PLAINS AND THEN AMPLIFY INTO A DEEPER TROUGH AS IT MOVES INTO THE
GREAT LAKES AND THEN ELONGATE TOWARDS THE TENNESSEE VALLEY. THIS
FEATURE WILL GENERALLY BE OF MODEST AMPLITUDE AND REMAIN
PROGRESSIVE, SO LARGE SCALE FORCING FOR ASCENT WILL BE MODEST AND
DRIVEN BY MID-LEVEL DIVERGENCE DOWNSTREAM OF THE TROUGH OVERLAPPING
MODEST WARM ADVECTION/ISENTROPIC ASCENT. THE RESULT OF THIS WILL BE
AXES OF BOTH LIGHT FREEZING RAIN AND SNOW IN MANY AREAS FROM
EASTERN MT THROUGH THE WESTERN GREAT LAKES. WPC PROBABILITIES FOR
2"+ OF SNOWFALL ARE AS HIGH AS 30-50% D2 ACROSS CENTRAL/NORTHERN
MN, AND SIMILAR FOR PARTS OF THE U.P. AND WESTERN L.P. OF MI D3.
FOR FREEZING RAIN, WPC PROBABILITIES ARE AS HIGH AS 30% FOR 0.1"
IN WESTERN ND ON D1, BUT ARE GENERALLY LESS THAN 10% ELSEWHERE
THROUGH THE PERIOD. HOWEVER, LIGHT FREEZING RAIN ACCRETING ABOVE
0.01" IS POSSIBLE FOR MUCH OF MONTANA AND THE DAKOTAS.
WEISS
...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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page