219
FOUS11 KWBC 212004
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 PM EST TUE JAN 21 2025
VALID 00Z WED JAN 22 2025 - 00Z SAT JAN 25 2025
..GREAT LAKES
DAYS 1-3...
UPPER TROUGHING CENTERED NEAR THE DAVIS STRAIT WILL SEND
SHORTWAVES AROUND ITS BASE ACROSS THE GREAT LAKES FOR THE NEXT
COUPLE OF DAYS, MAINTAINING THE LAKE-EFFECT SNOW WITH SOME BREAKS
IN BETWEEN EVENTS AND ACCENTUATED WITH A BROADER AREA OF LIGHT
SNOW. ONGOING HEAVY SNOW EAST OF LAKE ONTARIO INTO THE TUG HILL
WILL SLOWLY WEAKEN OVERNIGHT AS THE TROUGH AXIS PASSES THROUGH,
WHILE THE MULTI-BAND EVENT OVER THE UPPER GREAT LAKES CONTINUES IN
ADVANCE OF A SURFACE FEATURE. THAT AREA OF LOW PRESSURE WILL
TRAVERSE LAKE SUPERIOR AND HEAD EASTWARD THROUGH SOUTHERN CANADA,
SPREADING LIGHT SNOW OVER THE REGION TOMORROW INTO THURSDAY BEFORE
WEAKENING. 850MB TEMPERATURES ARE COLD (-20C AND LOWER) RESULTING
IN MORE THAN ENOUGH LAKE-850 DELTA-T WITH FLUFFY SNOW GIVEN THE
COLD AIR MASS.
THE HEAVIEST SNOW WILL BE ON D1 EAST OF LAKE ONTARIO AND ALSO OVER
NORTHWESTERN LOWER MI AND THE EASTERN U.P. ON SSW WINDS. WPC
PROBABILITIES FOR AT LEAST 8 INCHES OF SNOW OVER THE NEXT 72 HOURS
ARE HIGHEST IN THESE LOCATIONS (>40%) WITH A BROADER AREA OF >4"
PROBS >50% OVER THE NORTHWESTERN U.P. AND DOWNWIND OF LAKE ERIE
JUST SOUTH OF BUFFALO.
..NORTHERN ROCKIES/HIGH PLAINS
DAYS 1-3...
UPPER RIDGE AXIS OVER CA/OR WILL FAVOR NORTHERLY FLOW ACROSS THE
NORTHERN ROCKIES ONTO THE WESTERN HIGH PLAINS WITH A FEW WAVES OF
SNOWFALL OVER THE NEXT THREE DAYS. THOUGH MOISTURE IS RATHER
LIMITED, FAVORABLY-ENHANCED TERRAIN WILL HELP WRING OUT SEVERAL
ADDITIONAL INCHES OF THE LITTLE BELT AND BIG SNOWY MOUNTAINS INTO
THE BIGHORNS AND BLACK HILLS. LIGHTER SNOW IS EXPECTED FOR MUCH OF
THE REST OF THE REGION DAYS 1-2. THE NEXT SYSTEM ON D3 WILL FOCUS
OVER WESTERN MT AS THE 120-KT JET MOVES THROUGH. WPC PROBABILITIES
FOR AT LEAST 8 INCHES OF SNOW FOR THE PERIOD ARE HIGHEST OVER THE
AFOREMENTIONED MOUNTAINS.
..TEXAS, GULF COAST, AND SOUTHEAST
DAY 1...
...SIGNIFICANT AND HISTORIC WINTER STORM PUSHING THROUGH THE
SOUTHEAST/SOUTHERN MID-ATLANTIC TONIGHT...
THE WINTER STORM RESPONSIBLE FOR SIGNIFICANT AND RECORD-BREAKING
SNOWFALL OVER PARTS OF THE NORTHWEST GULF COAST WILL CONTINUE
EASTWARD AND NORTHEASTWARD TONIGHT. COLD AIR MASS SUPPORTS SNOW ALL
THE WAY INTO THE FL PANHANDLE WITH A MIX OF SLEET/FREEZING RAIN
JUST TO THE SOUTH OVER THE EASTERN PORTIONS OF THE I-10 CORRIDOR
AND ALONG THE I-95 CORRIDOR FROM NEAR CHARLESTON SOUTHWARD TO SOUTH
OF JACKSONVILLE. FOR THE PERIOD AFTER 00Z TONIGHT, SNOW WILL
SPREAD QUICKLY INTO EASTERN NC (AND EVEN UP INTO SOUTHEAST MA/CAPE
COD/ISLANDS) WITH THE SOUTHEAST IN THE RRQ OF A 200KT JET EXITING
THE EAST COAST INTO ATLANTIC CANADA AND A STRONG BAROCLINIC ZONE
JUST OFFSHORE AS THE ARCTIC AIR HAS BEEN ENTRENCHED TO THE COAST.
QUESTION REMAINS HOW MUCH MIXING THERE WILL BE ON THE
SOUTHERN/SOUTHEASTERN SIDE (SOUTHEAST GA/COASTAL SC/NORTHERN FL)
AND HOW QUICKLY THERE MAY BE PTYPE TRANSITION. SO FAR FOR THIS
STORM, THINGS HAVE BEEN COLDER RATHER THAN WARMER SO HAVE NUDGED IN
THIS DIRECTION FOR THE FIRST FEW PERIODS OF THIS FORECAST
(STARTING 00Z TONIGHT). WITH THE LONG POSITIVELY-TILTED TROUGH AXIS
APPROACHING THE EAST COAST 00-06Z TONIGHT, BROAD SW FLOW WILL
CONTINUE TO FUNNEL MOISTURE UP AND OVER THE COLD DOME WITH ENHANCED
FGEN OUT OF SOUTHEAST GA NORTHEASTWARD TO THE NC OUTER BANKS.
THERE, WPC PROBABILITIES FOR AT LEAST 4 INCHES OF SNOW ARE >30%
AND EVEN >50% OVER EASTERN NC.
COLDER AIR WILL CONTINUE TO PUSH THROUGH THE FL PANHANDLE THIS
EVENING WITH A MIX CHANGING TO SNOW INTO THE TALLAHASSEE AREA WHERE
WPC PROBABILITIES FOR AT LEAST AN INCH OF SNOW ARE >50% (EXTENDING
NORTHEASTWARD ACROSS SOUTHEASTERN GA AND INCREASING TO >70%. TO
THE SOUTH/SOUTHEAST, A MIX OF SLEET/FREEZING RAIN WILL LIKELY
RESULT IN A ZONE OF ICING OVER NORTHEASTERN GA INTO
SOUTHEASTERN/COASTAL GA/SC (ROUGHLY TLH-CHS-JAX-GNV) WHERE ENOUGH
WAA ABOVE THE SURFACE MAY PREVENT A CHANGEOVER TO ALL SNOW UNTIL
PERHAPS THE END OF THE EVENT. WPC PROBABILITIES OF AT LEAST A
HUNDREDTH OF AN INCH OF ICE ARE >30% OVER NORTHERN FL INTO
SOUTHEASTERN GA AND UP TO CHARLESTON, SC. WITHIN THIS REGION, WPC
PROBABILITIES FOR AT LEAST 0.10" ICING ARE HIGHEST (>30%) BETWEEN
TLH AND JAX NORTHWARD TO AROUND BRUNSWICK, GA.
TRAVEL WILL BE SEVERELY IMPACTED TONIGHT IN MUCH OF THE REGION.
SEE OUR KEY MESSAGES FOR MORE INFORMATION THAT COVER THIS SYSTEM AS
WELL AS THE EXTREME COLD OVER MUCH OF THE EASTERN HALF OF THE
LOWER 48.
FRACASSO
...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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