990
FOUS11 KWBC 180834
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
334 AM EST SAT JAN 18 2025
VALID 12Z SAT JAN 18 2025 - 12Z TUE JAN 21 2025
..GREAT LAKES
DAYS 1-3...
STRONG LOW PRESSURE TRACKING THROUGH SOUTHEAST CANADA WILL ESCORT
A STRONG ARCTIC FRONT THROUGH THE GREAT LAKES TODAY THAT WILL
REVITALIZE THE LES MACHINE THROUGHOUT THE REGION TODAY. STRONG
NWRLY FLOW WITH EXCEPTIONAL CAA WILL TRIGGER LES BANDS FROM THE
U.P. OF MICHIGAN ON SOUTH ALONG THE WESTERN-MOST PORTIONS OF
MICHIGAN'S MITTEN. FARTHER EAST, A SLUG OF MOISTURE ALOFT WILL RUN
PARALLEL TO THE ARCTIC FRONT AS IT RACES EAST TODAY WITH THE
CHAUTAUQUA RIDGE AND THE TUG HILL THE MORE FAVORED LOCATIONS FOR
LOCALLY HEAVY SNOW BEGINNING THIS MORNING AND CONCLUDING BY
SATURDAY EVENING. WPC PROBABILITIES THROUGH 12Z SUNDAY SHOW
MODERATE-TO-HIGH CHANCES (50-70%) FOR SNOWFALL TOTALS >4" IN THE
TUG HILL WHILE THERE ARE LOW-TO-MODERATE CHANCES (30-50%) FOR >4"
SNOWFALL AMOUNTS FROM NORTHEAST OHIO TO ALONG THE CHAUTAUQUA
RIDGE. PORTIONS OF THE EASTERN MICHIGAN U.P. AND THE PORCUPINES
ALSO SPORT MODERATE CHANCES (40-60%) FOR SNOWFALL AMOUNT >4". AS
WINDS ACCELERATE OVER THE GREAT LAKES ON SUNDAY AND INVERTED
TROUGHING ENSUE OVER LAKE SUPERIOR, LES BANDS WILL INCREASE IN
BOTH COVERAGE AND INTENSITY IN THE USUAL SNOW BELTS OF THE
MICHIGAN U.P. AND THE NORTHERN MOST PORTIONS OF MICHIGAN'S MITTEN.
INCLUDING SUNDAY AND MONDAY, WPC PROBABILITIES DEPICTED HIGH
CHANCES (>70%) FOR SNOWFALL > THAN 8" ALONG THE EASTERN MOST AREAS
OF MICHIGAN'S U.P. AND JUST NORTH OF THE TRAVERSE CITY AREA.
SINGLE-BANDED LES LOOK TO EMERGE OFF OF LAKES ERIE AND ONTARIO
MONDAY EVENING AND GENERATE HEAVY SNOWFALL RATES OF 1-2"/HR THROUGH
THE DAY ON TUESDAY.
..COLORADO ROCKIES AND HIGH PLAINS
DAY 1...
MOUNTAIN SNOW WILL CONTINUE OVER THE EASTERN SLOPES AND FRONT RANGE OF
THE COLORADO AND NEW MEXICO ROCKIES, INCLUDING THE ADJACENT HIGH
PLAINS ALONG THE I-25 CORRIDOR TODAY. THE SHORTWAVE TROUGH TRACKING
SOUTH THROUGH THE INTERMOUNTAIN WEST THIS MORNING WILL GENERATE
SYNOPTIC-SCALE LIFT OVER COLORADO AND NORTHERN NEW MEXICO WHICH
WILL ALSO HAVE LOW-LEVEL, POST-FRONTAL UPSLOPE NERLY FLOW WITH A
1050MB DOME OF HIGH PRESSURE MOVING OVER MONTANA ON SATURDAY.
SNOWFALL RATES AROUND 1"/HR ARE POSSIBLE ALONG THE RATON MESA EARLY
SATURDAY AND WILL WORK THEIR WAY SOUTH ALONG THE SPINE OF THE
SANGRE DE CRISTO SATURDAY AFTERNOON. SATURDAY'S SNOW PROBS FOR >4"
ARE HIGH (60-80%) OVER THE FRONT RANGE FROM PIKES PEAK ON SOUTH TO
THE RATON MESA, WHILE AREAS ALONG I-25 HAVE LOW-TO-MODERATE
CHANCES (20-40%) FOR >4" OF SNOWFALL.
..CENTRAL APPALACHIANS, MID-ATLANTIC AND NORTHEAST
DAYS 1-3...
...SIGNIFICANT WINTER STORM TO PRODUCE A SWATH OF HEAVY SNOW FROM
THE CENTRAL APPALACHIANS AND NORTHERN MID-ATLANTIC TO THE NORTHEAST
SUNDAY AND MONDAY...
AS MODEL GUIDANCE CONTINUES TO COME INTO BETTER AGREEMENT ON THE
OVERALL SYNOPTIC-SCALE SETUP, IT IS BECOMING CLEARER THAT A
SIGNIFICANT WINTER STORM IS LIKELY TO PRODUCE HEAVY SNOW SNOW FROM
AS FAR SOUTH AND WEST AS WESTERN KENTUCKY TO AS FAR NORTH AS
NORTHERN MAINE. AS THE ARCTIC FRONT APPROACHES SATURDAY NIGHT, THE
FRONT WILL BE DRAPED OVER THE MID-ATLANTIC WHILE AT THE SAME TIME,
STRONG UPPER-LEVEL DIVERGENCE ENSUES ALOFT COURTESY OF A ~150KT
250MB JET STREAK'S DIFFLUENT LEFT-EXIT REGION IS IN PLACE. AS
850-700MB WAA INCREASES OVER THE MID-ATLANTIC, IT WILL CLASH WITH
THE APPROACHING ARCTIC AIR-MASS TO THE NORTH, RESULTING IN A BAND
OF HEAVY SNOW THAT INITIALLY STARTS OUT OVER THE LAUREL HIGHLANDS
AND ALLEGHENY HIGHLANDS EARLY SUNDAY MORNING, THEN SPREADS OVER
NORTHERN MD AND SOUTHERN PA LATER ON THAT MORNING. AS THE 850-700MB
FGEN INCREASES THROUGHOUT THE DAY, SNOWFALL RATES WILL INCREASE
ACROSS EASTERN PA, NORTHERN NJ, AND THE LOWER HUDSON VALLEY THROUGH
SUNDAY EVENING. 00Z HREF DOES SUGGEST THERE ARE LOW-TO-MODERATE
CHANCES (20-50%) FOR 1"/HR SNOWFALL RATES DURING THE DAY ON SUNDAY.
BY 00Z MONDAY, THE 850MB LOW WILL TRACK OVER LONG ISLAND AND HEAD
FOR THE NEW ENGLAND COAST WITH THE AXIS OF HEAVY SNOW RESIDING
ALONG THE WESTERN FLANK OF THE 850MB CIRCULATION. HEAVY SNOW WILL
UNFOLD ACROSS PORTIONS OF COASTAL NEW ENGLAND SUNDAY NIGHT WHERE
SNOWFALL RATES >1"/HR ARE POSSIBLE. THE STORM RACES NORTHEAST PAST
NOVA SCOTIA BY MONDAY MORNING WITH LINGERING PERIODS OF SNOW
THROUGHOUT PARTS OF MAINE GRADUALLY TAPERING OFF BY MIDDAY MONDAY.
LATEST WPC GUIDANCE DEPICTS A SWATCH OF MODERATE-TO-HIGH CHANCES
(50-70%) FOR SNOWFALL >4" FROM CENTRAL WV ON NORTH AND EAST THROUGH
CENTRAL PA. FROM THE POCONOS ON NORTH AND EAST THROUGH THE LOWER
HUDSON VALLEY, THE BERKSHIRES, AND INTO BOTH THE WORCESTER HILLS
AND WHITE MOUNTAINS, THERE ARE MODERATE-TO-HIGH ODDS (50-70%) FOR
SNOWFALL >6", AS WELL AS MODERATE CHANCES (4-60%) FOR SNOWFALL >8".
NOTE THAT WPC PROBABILITIES FOR >12" ARE GENERALLY <10%,
INDICATING MOST AREAS ARE UNLIKELY TO RECEIVE A FOOT OF SNOWFALL,
ALTHOUGH LOCALIZED AMOUNTS IN THE ALLEGHENY HIGHLANDS AND PARTS OF
INTERIOR NEW ENGLAND CANNOT FULLY BE RULED OUT. LATEST WSSI SHOWS A
HEALTHY SWATH OF MODERATE IMPACTS FROM NORTHERN MD THROUGH THE
LOWER SUSQUEHANNA VALLEY, THE DELAWARE VALLEY, THE TRI-STATE AREA,
AND INTO PORTIONS OF SOUTHERN NEW ENGLAND. HAZARDOUS DRIVING
CONDITIONS ARE ANTICIPATED IN THESE AREAS ON SUNDAY. WITH BITTERLY
COLD TEMPERATURES SPILLING IN FOR THE UPCOMING WORK-WEEK, SNOW AND
INSTANCES OF RE-FREEZING/BLACK ICE ARE LIKELY TO STICK AROUND FOR
MUCH OF THE WEEK IN WAKE OF THIS WINTER STORM.
..SOUTHERN PLAINS & GULF COAST
...DISRUPTIVE WINTER STORM GROWING IN CONFIDENCE ACROSS THE
SOUTHERN U.S. NEXT WEEK...
DAY 3...
FOR A WINTER STORM TO UNFOLD FROM AS SOUTH AS THE SAN ANTONIO AREA
ON EAST TO THE CENTRAL GULF COAST, THE FIRST INGREDIENT IS FOR AN
EXCEPTIONALLY COLD AIR-MASS TO BE LOCKED IN PLACE. WITH THE ARRIVAL
OF THE ARCTIC AIR-MASS THIS WEEKEND, BONE-CHILLING TEMPERATURES
WILL BE ANCHORED IN PLACE BY A DOME OF HIGH PRESSURE THAT NAEFS
SHOWS IS ABOVE THE 97.5 CLIMATOLOGICAL PERCENTILE AS OF 12Z MONDAY
OVER THE LOWER MS VALLEY. BY 00Z TUESDAY, 850MB TEMPERATURES REMAIN
BELOW THE 2.5 CLIMATOLOGICAL PERCENTILE AND SUBFREEZING 850MB TEMPS
PROTRUDING AS FAR SOUTH AS THE GULF COAST. MEANWHILE, A POSITIVELY
TILTED 500MB TROUGH TRACKING THROUGH THE SOUTHWEST WILL WORK IN
TANDEM WITH THE SUBTROPICAL JET TO INCREASE UPPER-LEVEL DIVERGENCE
OVER TEXAS MONDAY AFTERNOON. IN ADDITION, SWRLY 850MB FLOW WILL
DELIVER LOW-LEVEL MOISTURE NORTHWARD WHILE AT THE SAME TIME, THE
850MB WAA OVER SOUTH TEXAS WILL OVERRUN THE ARCTIC AIR-MASS IN
PLACE OVER TEXAS. THIS WILL RESULT IN THE BEGINNING OF AN ICY
WINTRY MIX OVER SOUTH-CENTRAL TEXAS AND EVENTUALLY SPREAD EAST
TOWARDS THE UPPER TEXAS COAST AND LOWER MISSISSIPPI VALLEY BY EARLY
TUESDAY MORNING.
WPC PROBABILITIES SHOW MODERATE CHANCES (40-60%) FOR >0.01" OF ICE
ACCUMULATIONS IN SOUTH-CENTRAL TEXAS THROUGH 12Z TUESDAY, WHICH
WOULD RESULT IN SLICK AND DANGEROUS ROAD CONDITIONS FOR THE TUESDAY
MORNING COMMUTE. FARTHER NORTH, WPC PROBABILITIES SHOW LOW-CHANCE
ODDS (10-30%) FOR SNOWFALL >2" IN PARTS OF EASTERN TEXAS AND
WESTERN LOUISIANA. IT IS WORTH NOTING THAT THE SCOPE OF THIS
DISCUSSION GOES THROUGH 12Z TUESDAY, SO EXPECT SNOWFALL PROBABILITIES
TO INCREASE OVER THE NEXT 24 HOURS. PLEASE BE SURE TO VISIT WPC'S
MEDIUM RANGE DISCUSSION AND OUR KEY MESSAGES FOR MORE DETAILS ON
THE POTENTIAL IMPACTS THROUGHOUT THE SOUTH LATER THIS WEEK.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page