131
FXUS01 KWBC 210421
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1120 PM EST FRI DEC 20 2024
VALID 12Z SAT DEC 21 2024 - 12Z MON DEC 23 2024
...PERIODS OF MODERATE TO HEAVY RAINFALL NEAR THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA...
...RECORD WARMTH POSSIBLE ACROSS PARTS OF THE WEST SATURDAY AND
SUNDAY...
THE GENERAL FLOW PATTERN FAVORS AN UPPER LEVEL TROUGH ACROSS THE
EASTERN PACIFIC OCEAN, RIDGING ALOFT IN THE WEST, AND TROUGHING
ALOFT IN THE EASTERN UNITED STATES. THE CONSEQUENCE OF THIS
PATTERN WILL BE SOME RAINFALL ALONG THE WEST COAST, WARMTH ACROSS
THE INTERMOUNTAIN WEST, AND COLD ACROSS PORTIONS OF THE EAST.
STARTING OUT WEST, SKIRMISHES OF RAIN ALONG THE WEST COAST ARE
EXPECTED SATURDAY AS LOW PRESSURE SYSTEMS MOVE NORTHWARD OFFSHORE
THE WEST COAST. ON SATURDAY AND SUNDAY, WEAKENING FRONTS MOVE
EASTWARD, PUSHING A COUPLE BATCHES OF RAINFALL INTO THE THROUGH
THE PACIFIC NORTHWEST, NORTHERN INTERMOUNTAIN WEST, AND NORTHERN
CALIFORNIA, WITH SNOWFALL EXPECTED AT HIGHER ELEVATIONS. HIGH
TEMPERATURES ACROSS NORTHERN PORTIONS OF THE WEST WILL RISE INTO
THE 40S AND 50S, HIGH ENOUGH TO THREATEN RECORD HIGH TEMPERATURES
ON SATURDAY. ACROSS THE SOUTHWEST, HIGH TEMPERATURES SHOULD RISE
INTO THE 70S TO 80S SATURDAY AND 60S TO 70S ON SUNDAY, THREATENING
DAILY RECORD HIGH TEMPERATURES IN AND NEAR SOUTHERN ARIZONA AND
SOUTHERN CALIFORNIA.
MID-CONTINENT, A SEASONABLY STRONG AND COLD HIGH PRESSURE SYSTEM
MIGRATES FROM THE GREAT LAKES INTO THE EAST, BRINGING BELOW
AVERAGE TEMPERATURES NEAR AND TO ITS EAST. FOR SOME AREAS OF THE
EAST, IT SHOULD BE THE COLDEST TEMPERATURES THUS FAR THIS WINTER.
WHEN COMBINED WITH CYCLONIC FLOW AROUND A LOW MOVING OFFSHORE THE
EAST COAST, LAKE EFFECT SNOWFALL IS EXPECTED NEAR THE GREAT LAKES,
PORTIONS OF THE APPALACHIANS, NORTHERN MID-ATLANTIC STATES, AND
NEW ENGLAND WHICH SLOWLY FADES SATURDAY AND SUNDAY. WINTER
WEATHER ADVISORIES ARE IN EFFECT IN PATCHES ACROSS THE EASTERN
GREAT LAKES, CENTRAL/SOUTHERN APPALACHIANS, NORTHERN MID-ATLANTIC
STATES, AND COASTAL NEW ENGLAND WITH A VERY LOCALIZED WINTER STORM
WARNING IS IN PLACE FOR PORTIONS OF DOWNEAST MAINE THROUGH MIDDAY
SATURDAY TO HELP ADVISE ON THE MODERATE TO HEAVY SNOWFALL
EXPECTED. A LOW PRESSURE SYSTEM DEVELOPING ACROSS THE UPPER
MIDWEST AND GREAT LAKES SUNDAY INTO EARLY MONDAY IS EXPECTED TO
LEAD TO SNOWFALL WHICH INCREASES IN COVERAGE AND INTENSITY WITH
TIME FROM NORTH DAKOTA EASTWARD INTO MICHIGAN.
ROTH
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