916
FXUS01 KWBC 100815
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EST TUE DEC 10 2024
VALID 12Z TUE DEC 10 2024 - 12Z THU DEC 12 2024
...WIDESPREAD HEAVY RAIN THREAT EMERGING ACROSS THE CENTRAL TO
EASTERN GULF COAST REGION TODAY WILL SPREAD RAPIDLY UP THE ENTIRE
EAST COAST ON WEDNESDAY...
...ACTIVE LAKE EFFECT SNOWS TO BEGIN WEDNESDAY AND CONTINUE
THROUGH THURSDAY DOWNWIND OF THE LAKES...
...RECORD WARM MORNING LOWS LIKELY ALONG THE EAST COAST WEDNESDAY
MORNING...
...ARCTIC AIR TO SURGE SOUTH INTO THE NORTHERN PLAINS/UPPER
MISSISSIPPI VALLEY REGION LATE TUESDAY INTO WEDNESDAY...
...SANTA ANA WINDS ALONG WITH CRITICAL TO EXTREME FIRE WEATHER
DANGER ACROSS PORTIONS OF SOUTHERN CALIFORNIA...
THE UPPER-LEVEL FLOW PATTERN ACROSS MUCH OF NORTH AMERICA WILL
UNDERGO SIGNIFICANT AMPLIFICATION OVER THE NEXT FEW DAYS,
PRODUCING VARIOUS TYPES OF IMPACTFUL WEATHER ACROSS MAINLAND U.S.
THE MOST ACTIVE WEATHER IN TERMS OF PRECIPITATION AND WINDS WILL
BE THE PRIMARY FOCUS ALONG THE EAST COAST THROUGH THE NEXT COUPLE
OF DAYS. PRECIPITATION CURRENTLY FALLING ACROSS PORTIONS OF THE
SOUTHEAST IS IN ITS ORGANIZING STAGE AHEAD OF A DEVELOPING LOW
PRESSURE WAVE OVER THE MID-SOUTH ALONG A COLD FRONT. AS THE COLD
AIR BEHIND THE FRONT INTERACTS WITH A RAPIDLY AMPLIFYING UPPER
TROUGH, RAIN AND EMBEDDED THUNDERSTORMS WILL RAPIDLY EXPAND
NORTHEASTWARD DURING THE DAY WEDNESDAY AND UP THE ENTIRE EAST
COAST, PRODUCING A PERIOD OF WIDESPREAD HEAVY RAINFALL FROM THE
CENTRAL TO EASTERN GULF COAST, ACROSS THE SOUTHEAST, MID-ATLANTIC,
NORTHEAST AND NEW ENGLAND. WITH MUCH OF THESE AREAS CURRENTLY IN
MODERATE TO EXTREME DROUGHT CONDITIONS, THIS RAINFALL WILL BE
BENEFICIAL. STILL, GIVEN THE POTENTIAL FOR PERIODS OF HEAVY RAINS
OVER A SHORT PERIOD, THERE WILL BE A THREAT OF LOCALIZED FLASH
FLOODING, ESPECIALLY IN MORE URBANIZED REGIONS.
THE COLD FRONT ASSOCIATED WITH THIS RAPIDLY INTENSIFYING SYSTEM
WILL BECOME RATHER POTENT AS IT SWEEPS ACROSS THE EAST COAST
DURING THE DAY ON WEDNESDAY. THERE IS POTENTIAL FOR SOME VERY
STRONG THUNDERSTORMS TO FORM AHEAD OF THE FRONT TOGETHER WITH
HEAVY DOWNPOURS. MEANWHILE, DRASTICALLY COLDER AIR BEHIND THE
FRONT IS FORECAST TO PRODUCE ACCUMULATING SNOWFALL UP THE WESTERN
SLOPES OF THE APPALACHIANS ON WEDNESDAY TOGETHER WITH BLUSTERY
NORTHWESTERLY WINDS. THE SNOW WILL THEN SWEEP ACROSS INTERIOR NEW
ENGLAND THROUGH WEDNESDAY NIGHT INTO THURSDAY MORNING AS A POTENT
ELONGATED LOW PRESSURE SYSTEM RACES NORTHWARD INTO SOUTHEASTERN
CANADA.
WITH A WARM SOUTHERLY FLOW STRENGTHENING AHEAD OF THIS POTENT
FRONT, THERE IS THE POTENTIAL FOR WIDESPREAD RECORD HIGH MORNING
LOW TEMPERATURES ON WEDNESDAY ACROSS THE SOUTHERN MID-ATLANTIC,
MID-ATLANTIC AND PORTIONS OF THE NORTHEAST. IN THE WAKE OF THIS
FRONT, MUCH COLDER AIR WILL STREAM ACROSS THE GREAT LAKES FROM
WEST TO EAST BEGINNING ON WEDNESDAY. THIS WILL IGNITE ACTIVE
LAKE-EFFECT SNOWS, INITIALLY DOWNWIND OF LAKES SUPERIOR AND
MICHIGAN ON WEDNESDAY AND THEN DOWNWIND OF LAKES ERIE AND ONTARIO
WEDNESDAY NIGHT INTO EARLY THURSDAY. BEFORE THESE LAKE-EFFECT
SNOWS DIMINISH BY EARLY FRIDAY, SNOWFALL TOTALS OF 1 TO 2 FEET ARE
POSSIBLE IN THE FAVORED SNOW BELT ACROSS PORTIONS OF NORTHWEST AND
WESTERN NEW YORK STATE, FAR NORTHWEST PENNSYLVANIA, FAR
NORTHEASTERN OHIO, THE UPPER PENINSULA OF MICHIGAN AND THE WESTERN
PORTIONS OF THE LOWER PENINSULA OF MICHIGAN.
THE ABOVE-MENTIONED LAKE-EFFECT SNOWS WILL BE DRIVEN BY ARCTIC AIR
THAT WILL BE FIRST SURGING EAST SOUTHEASTWARD LATE TUESDAY INTO
EARLY WEDNESDAY ACROSS THE NORTHERN PLAINS INTO THE UPPER
MISSISSIPPI VALLEY AND THEN EASTWARD TROUGH THE GREAT LAKES INTO
THE OHIO VALLEY ON WEDNESDAY. WHILE THERE ARE NOT EXPECTED TO BE
ANY RECORDS WITH THIS ARCTIC OUTBREAK, TEMPERATURES WILL BE MUCH
BELOW AVERAGE ON WEDNESDAY ACROSS THE NORTHERN PLAINS INTO THE
UPPER MISSISSIPPI VALLEY. THESE MUCH BELOW AVERAGE TEMPERATURES
WILL THEN PUSH FARTHER SOUTHEAST INTO THE GREAT LAKES AND OHIO
VALLEY REGION ON THURSDAY. ACROSS THESE REGIONS, HIGH
TEMPERATURES WILL BE 10 TO 25 DEGREES BELOW AVERAGE DURING THE
HEIGHT OF THE COLD TEMPERATURES DURING WEDNESDAY AND THURSDAY.
IN CONTRAST TO THE WET AND COLD CONDITIONS ACROSS PORTIONS OF THE
NORTH-CENTRAL TO EASTERN U.S., DRY CONDITION AND MILDER
TEMPERATURES ARE IN STORE ACROSS THE WEST COAST, GREAT BASIN AND
ROCKIES REGION. THE DRY AIR, LOW RELATIVE HUMIDITIES TOGETHER
WITH THE LATEST EPISODE OF SANTA ANA WINDS ACROSS SOUTHERN
CALIFORNIA WILL PRODUCE CRITICAL TO LOCALLY EXTREME FIRE WEATHER
DANGER. THESE FIRE WEATHER CONDITIONS WILL BE MOST PROMINENT IN
THE HIGHER TERRAIN AREAS TO THE NORTH AND EAST OF THE LOS ANGELES
TO SAN DIEGO REGION. WINDS OF 35 TO 45 MPH IN THE VALLEYS AND
GUSTS OF 50 TO 65 MPH IN THE MOUNTAINS WILL HELP FAN ANY FIRES
THAT DO DEVELOP QUICKLY AND MAY REDUCE VISIBILITY WITH BLOWING
SMOKE AND DUST ADDING TO TRAVEL CONCERNS IN THE REGION. ACROSS
THESE AREAS, RED FLAG WARNINGS ARE CURRENTLY IN EFFECT, AFFECTING
NEARLY 13 MILLION PEOPLE.
BY EARLY ON THURSDAY, THE NEXT ROUND OF COASTAL RAIN AND MOUNTAIN
SNOW IS FORECAST TO REACH NORTHERN CALIFORNIA AS THE NEXT PACIFIC
CYCLONE ARRIVES.
KONG/ORAVEC
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