051
FXUS01 KWBC 041945
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 PM EST MON DEC 04 2023
VALID 00Z TUE DEC 05 2023 - 00Z THU DEC 07 2023
...EXCESSIVE RAINFALL AND INSTANCES OF FLOODING ARE LIKELY ACROSS
PARTS OF WESTERN WASHINGTON OREGON AND NORTHERN CALIFORNIA OVER
THE NEXT FEW DAYS...
...MODERATE UPSLOPE SNOW POTENTIAL FORECAST ACROSS THE CENTRAL
APPALACHIANS TUESDAY AFTERNOON INTO WEDNESDAY...
...WARMING TREND INCREASES ACROSS THE GREAT PLAINS THROUGH
MIDWEEK...
DIFFLUENCE ASSOCIATED WITH A DEEP UPPER-LEVEL TROUGH WILL DIRECT
ANOMALOUS MOISTURE INTO THE PACIFIC NORTHWEST FOCUSED ALONG
SURFACE COLD AND WARM FRONTS. SNOW LEVELS WILL BE HIGH ENOUGH THAT
MOST OF THE PRECIPITATION THAT OCCURS WILL BE IN THE FORM OF RAIN.
THUS, HEAVY RAINFALL IS EXPECTED ACROSS MUCH OF WESTERN WASHINGTON
AND NORTHWEST OREGON BEGINNING TONIGHT. THE OLYMPIC MOUNTAINS WILL
BE PARTICULARLY HARD HIT WITH A NUMBER OF DYNAMIC AND MOISTURE
INGREDIENTS COMING TOGETHER TO PRODUCE SEVERAL INCHES OF RAINFALL
THERE IN PARTICULAR, BUT ALSO OVER THE NORTHERN CASCADES AND DOWN
THE COAST INTO NORTHWESTERN OREGON. THERE IS A CORRESPONDING
MODERATE RISK (AT LEAST 40%) OF EXCESSIVE RAINFALL LEADING TO
FLASH FLOODING OVER THE OLYMPICS FOR TONIGHT. THE PRIMARY HEAVY
RAIN THREAT SHIFTS INTO COASTAL PORTIONS OF SOUTHERN WASHINGTON
AND INTO OREGON ON TUESDAY WHERE A FEW MORE INCHES MAY ACCUMULATE.
A PAIR OF SLIGHT RISKS (AT LEAST 15%) OF EXCESSIVE RAINFALL ARE IN
EFFECT FOR THE AFOREMENTIONED COASTAL AREAS AS WELL AS UPSLOPE
PORTIONS OF THE NORTHERN CASCADES.
MEANWHILE, A DEEPENING POSITIVELY TILTED TROUGH SWINGING THROUGH
THE MIDWEST WILL PROMOTE SNOWFALL OVER PORTIONS OF THE CENTRAL
APPALACHIANS BEGINNING TUESDAY AFTERNOON. MODERATE SNOW IS
POSSIBLE OVER PORTIONS OF THE SOUTHERN ALLEGHENY AND APPALACHIAN
PLATEAU WITH LESSER AMOUNTS ELSEWHERE IN THE REGION. THINGS SHOULD
BEGIN TO WIND DOWN BY WEDNESDAY EVENING. UPSTREAM OF HERE, A LARGE
RIDGE WILL DEVELOP OVER THE CENTRAL PART OF THE COUNTRY AND
SUPPORT A WARMING TREND OVER THE NEXT SEVERAL DAYS. SOME HIGH
TEMPERATURE ANOMALIES IN THE NORTHERN/CENTRAL PLAINS WILL LIKELY
RANGE FROM 15-30 DEGREES ABOVE AVERAGE WITH SOME ISOLATED
DEPARTURES ECLIPSING THAT RANGE. THE HEAVY SNOW THREAT SHOULD
DIMINISH ACROSS NORTHERN NEW ENGLAND TONIGHT WHILE THE INCITING
SHORTWAVE ENERGY AND ASSOCIATED LOW PRESSURE SYSTEM MOVE OFFSHORE.
KEBEDE
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