831
FOUS11 KWBC 310710
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 AM EST SAT JAN 31 2026
VALID 12Z SAT JAN 31 2026 - 12Z 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...
SHARP MID-LEVEL TROUGH OVER THE MID-MS VALLEY EARLY THIS MORNING
WILL CLOSE OFF INTO A POTENT UPPER LOW OVER MIDDLE TN BY 12Z. THE
PATTERN OVER THE EAST COAST WILL FEATURE AN INCREASINGLY AMPLIFIED
PATTERN (E.G., STRENGTHENING S-SHAPED UPPER JET) THAT WILL SUPPORT
EXPLOSIVE CYCLOGENESIS OFF THE CAROLINA COAST THIS
EVENING/OVERNIGHT. WITH AN ARCTIC AIR MASS ALREADY IN PLACE, NEARLY
ALL OF THE PRECIPITATION WILL BE SNOW EVEN AT ONSET. THE SYSTEM
WILL QUICKLY LIFT UP THE COAST (OUTSIDE THE 40/70 BENCHMARK) AND
CLIP SOUTHEASTERN NEW ENGLAND AS IT RACES INTO ATLANTIC CANADA
TOMORROW.
FIRST PART OF THE SYSTEM IS UNDERWAY OVER THE SOUTHERN
APPALACHIANS WITH LIGHT TO MODEST SNOW OVER THE SMOKEYS INTO SW VA
BENEATH LOWER-LEVEL FGEN AND INCOMING HEIGHT FALLS/PVA. SNOW WILL
EXPAND SOUTHWARD TODAY OVER WNC AND UPSTATE SC AS WELL AS NORTHEAST
GA AS THE UPPER LOW TRACKS OVER ATL TO CHS BY THIS EVENING. TO ITS
NORTH, NEAR THE PATH OF THE DEVELOPING 850MB LOW, THE SNOW COULD
FALL HEAVY AT TIMES TODAY WITH 1"/HR RATES POSSIBLE (10-40% CHANCE
PER THE CAM GUIDANCE) INTO THE CHARLOTTE METRO. AS THE UPPER LOW
REACHES THE COAST AROUND 06Z SUN, BANDED SNOW COULD SINK
SOUTHEASTWARD INTO NORTHEASTERN SC (MYRTLE BEACH/THE GRAND STRAND).
BY THIS TIME, THE COASTAL LOW WILL HAVE BEGUN ITS RAPID
INTENSIFICATION, WHICH LEADS INTO THE OTHER PART OF THE SYSTEM.
WITH THE COASTAL LOW INTENSIFYING THROUGH THE 990S TO 970S MB, N
TO NE FLOW AT THE SURFACE OVER EASTERN AND NORTHEASTERN NC INTO
EXTREME SOUTHEASTERN VA WILL INCREASE AS SNOW CONTINUES TO FALL.
THE INCREASING 850MB NORTHEASTERLY/EASTERLY FLOW, TAPPING INTO THE
GROWING THETA-E RIDGE OFFSHORE, COUPLED WITH WAA AND STRENGTHENING
925-700MB FGEN, WILL SUPPORT >1"/HR RATES OVER EASTERN NC AFTER 00Z
SUN. DEFORMATION AXIS SHOULD PIVOT WEST OF THE SURFACE LOW AND THE
COLD CONVEYOR SETS UP ACROSS THE ATLANTIC AND INTO THE EASTERN
CAROLINAS TO SUPPORT THOSE RATES. CROSS-SECTIONS INDICATE A BROAD
REGION OF FAVORABLE CONDITIONS FOR CSI, OR EVEN CI (THUNDERSNOW),
WHICH IS NOT UNUSUAL IN HIGHLY DYNAMIC AND RAPIDLY INTENSIFYING
SYSTEMS. THE COLUMN IS QUITE COLD, AND SLRS SHOULD BE WELL ABOVE
CLIMO WITH A DEEP DGZ (>13:1 TO NEAR 20:1). THESE HEAVY SNOW RATES
WILL BE ACCOMPANIED BY STRONG WINDS THAT MAY GUST 35-50 MPH, HIGHER
AT THE COAST, SUGGESTING NEAR-BLIZZARD CONDITIONS IN MANY AREAS.
ONE QUESTION IN THE FORECAST, PER THE 00Z GUIDANCE, IS WHAT
HAPPENS IN BETWEEN THESE TWO MAIN DRIVERS OF HEAVIER SNOW AREAS;
I.E., IN THE I-85/95 CORRIDORS IN NC. SOME CAM GUIDANCE SHOWS AN
EXTREME MIN (NEAR ZERO SNOW) WHILE OTHER GUIDANCE SHOWS AT LEAST
SEVERAL INCHES. CAM GUIDANCE COULD BE OVERDOING THE MESOSCALE
RESPONSE OF OSCILLATORY SUBSIDENCE/LIFT SURROUNDING THE SYSTEM, BUT
IT CERTAINLY IS UNUSUAL TO SEE THIS MUCH SPREAD JUST BEFORE THE
START OF THE EVENT. TRIMMED DOWN THE AMOUNTS HERE FROM THE PREVIOUS
FORECAST BUT NOT TO THE EXTENT OF THE 00Z CAMS.
BY SUNDAY AFTERNOON THE LOW WILL PULL AWAY BRINGING AN END TO THE
SNOWFALL AND LEAVING JUST COLD WINDY CONDITIONS IN ITS WAKE. TO THE
NORTHEAST, DESPITE A TRACK JUST OUTSIDE THE 40/70 BENCHMARK, THE
EXPANSIVE SYSTEM WILL LIKELY CLIP FAR SOUTHEAST MASSACHUSETTS
(SOUTHEAST OF I-95) AND CAPE COD AND THE ISLANDS WHERE PERIODS OF
MODERATE SNOW ARE 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 AT LEAST 6 INCHES OF SNOW ARE >50% OVER MUCH
OF WESTERN NC, ACROSS THE BORDER TO UPSTATE SC, SOUTHEASTWARD TO
THE COAST, AND THE NORTHEASTWARD UP THE COAST INTO EXTREME
SOUTHEASTERN VA. LOWER PROBABILITIES AROUND 30% EXIST ALONG THE VA
BORDER AND OVER SOUTHWESTERN SC. MESOSCALE BANDS WILL LIKELY
ENHANCE SNOWFALL OVER SOME AREAS RESULTING IN >10-12" SNOW. A
BROADER AREA OF LIGHT SNOW IS EXPECTED SURROUNDING THE SYSTEM, WITH
WPC PROBABILITIES FOR AT LEAST 1" OF SNOW >50% AS FAR WEST AS
ATLANTA, SOUTH TO NEAR SAVANNAH, AND ON THE NORTH SIDE UP TO
RICHMOND, VA AND SALISBURY, MD ON THE DELMARVA. IN MA, WPC
PROBABILITIES FOR AT LEAST 4 INCHES OF SNOW ARE >30% OVER THE CAPE
AND MARTHA'S VINEYARD BUT >50% OVER NANTUCKET.
KEY MESSAGES ARE IN EFFECT FOR THIS STORM, AND ARE LINKED BELOW
(KEY MESSAGE #2).
..NORTHERN PLAINS THROUGH THE UPPER MIDWEST AND GREAT LAKES
DAYS 1-3...
AND ADVANCING WARM FRONT OVER THE WESTERN HIGH PLAINS THIS MORNING
WILL CONTINUE EASTWARD, BRINGING THE CHANCE FOR SOME SNOW AND
FREEZING RAIN AS MILDER PACIFIC AIR OVERRUNS THE COLD SURFACE. THE
SYSTEM WILL CONTINUE EASTWARD SUNDAY INTO THE WESTERN GREAT LAKES
AND THROUGH MI TO THE EASTERN GREAT LAKES MONDAY. AMOUNTS WILL BE
LIGHT, GENERALLY 1-3", AS THE SYSTEM REMAINS PROGRESSIVE. WPC
PROBABILITIES FOR AT LEAST 4" ARE AROUND 10% OVER PORTIONS OF THE
RED RIVER VALLEY (ND/MN BORDER) AND PERHAPS THE KEWEENAW PENINSULA
WIT SOME LAKE ENHANCEMENT AFTER THE FRONT MOVES TO THE EAST.
FRACASSO/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
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