505
FXUS01 KWBC 130748
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 AM EST FRI DEC 13 2024
VALID 12Z FRI DEC 13 2024 - 12Z SUN DEC 15 2024
...ATMOSPHERIC RIVER TO BRING VERY HEAVY RAINFALL AND POSSIBLE
FLOODING AS WELL AS HIGH ELEVATION MOUNTAIN SNOW TO THE WEST
COAST...
...HEAVY MOUNTAIN SNOW FORECAST FOR PORTIONS OF THE GREAT BASIN
AND NORTHERN ROCKIES SATURDAY...
...POTENTIALLY IMPACTFUL WINTRY MIX WITH FREEZING RAIN EXPECTED
ACROSS THE MIDDLE MISSOURI VALLEY AND UPPER MIDWEST SATURDAY...
AN ATMOSPHERIC RIVER EVENT WILL BRING VERY HEAVY RAIN, MOUNTAIN
SNOW, AND GUSTY WINDS TO PORTIONS OF SOUTHERN OREGON AND
NORTHERN/CENTRAL CALIFORNIA FRIDAY INTO SATURDAY. A SLIGHT RISK OF
EXCESSIVE RAINFALL (LEVEL 2/4) HAS BEEN ISSUED ALONG PORTIONS OF
THE COASTAL RANGES OF NORTHERN CALIFORNIA WHERE LOCALLY HEAVY
RAINFALL RATES OF 0.5" PER HOUR AND RAINFALL TOTALS OF 3-5", WITH
ISOLATED HIGHER AMOUNTS UPWARDS OF 7", MAY LEAD TO SOME INSTANCES
OF FLOODING DURING THE HEIGHT OF THE EVENT FRIDAY
EVENING/OVERNIGHT INTO SATURDAY MORNING. VERY HEAVY MOUNTAIN SNOW
IS EXPECTED AT HIGHER ELEVATIONS (GENERALLY OVER 5000-6000 FEET)
OF THE COASTAL RANGES AND FOR THE SIERRA NEVADA. WINTER STORM
WARNINGS HAVE BEEN ISSUED FOR FORECAST SNOWFALL TOTALS OF 1-2
FEET, LOCALLY HIGHER. IN ADDITION TO THE HEAVY PRECIPITATION,
STRONG, GUSTY WINDS ARE ALSO EXPECTED, PARTICULARLY FOR COASTAL
LOCATIONS. A BROADER AREA OF MORE MODERATE RAINFALL STRETCHES
ACROSS THE PACIFIC NORTHWEST AND SOUTH ALONG COASTAL CALIFORNIA.
SOME MODERATE TO HEAVY SNOW IS ALSO FORECAST FURTHER NORTH THROUGH
THE CASCADES WHERE 4-8", LOCALLY HIGHER, CAN BE EXPECTED. THE
SYSTEM WILL CONTINUE EASTWARD LATE FRIDAY AND INTO THE DAY
SATURDAY, SPREADING MOISTURE AND PRECIPITATION CHANCES FURTHER
INLAND OVER THE GREAT BASIN AND NORTHERN ROCKIES. A MIX OF RAIN
AND SNOW CAN BE EXPECTED AT LOWER ELEVATIONS WITH SNOW, HEAVY AT
TIMES, FOR HIGHER MOUNTAIN ELEVATIONS. WINTER STORM WATCHES HAVE
BEEN ISSUED FOR THE MOUNTAINS OF CENTRAL IDAHO WHERE THE HEAVIEST
SNOW IS EXPECTED WITH FORECAST TOTALS OF 6-12".
TO THE EAST, AN UPPER-LEVEL WAVE PASSING FROM THE ROCKIES AND OVER
THE PLAINS WILL HELP TO ORGANIZE A SURFACE FRONTAL SYSTEM AND
ENCOURAGE MOIST, SOUTHERLY RETURN FLOW FROM THE GULF OF MEXICO.
SHOWERS AND THUNDERSTORMS ARE FORECAST AHEAD OF AN EASTWARD MOVING
COLD FRONT ACROSS EASTERN PORTIONS OF THE CENTRAL/SOUTHERN PLAINS
ON FRIDAY. MORE WIDESPREAD STORMS WITH MODERATE TO LOCALLY HEAVY
RAINFALL ARE EXPECTED ON SATURDAY AS THE SYSTEM CONTINUES INTO THE
MIDDLE MISSISSIPPI/LOWER OHIO VALLEY. SOME POTENTIALLY IMPACTFUL
WINTER WEATHER IS FORECAST FURTHER NORTH ACROSS THE MIDDLE
MISSOURI VALLEY AND INTO PORTIONS OF THE UPPER MIDWEST WHERE WARM,
MOIST AIR OVERRIDING COLDER TEMPERATURES WILL LEAD TO A WINTRY MIX
FRIDAY AFTERNOON THROUGH SATURDAY. SNOW/SLEET ACCUMULATIONS SHOULD
REMAIN LIGHT, BUT SOME FREEZING RAIN ACCRETIONS ARE ALSO EXPECTED.
THESE ACCRETIONS MAY BE GREATER THAN 0.1" OVER EASTERN IOWA WHICH
COULD LEAD TO SOME TREE DAMAGE AND POWER OUTAGES. REGARDLESS, THE
WINTRY MIX WILL AT LEAST LIKELY LEAD TO SOME TRAVEL TROUBLES
ACROSS THE REGION.
ELSEWHERE, MOST LAKE EFFECT SNOW WILL BE TAPERING OFF FRIDAY
MORNING FOR THE GREAT LAKES EXCEPT DOWNWIND OF LAKE ONTARIO WHERE
AN ADDITIONAL 6-12" CAN BE EXPECTED THROUGH THE DAY FRIDAY. SOME
LIGHT TO MODERATE SNOW SHOWERS WILL ALSO CONTINUE THROUGH THE DAY
FRIDAY FOR THE CENTRAL ROCKIES AS A COLD FRONT MOVES THROUGH THE
REGION. HIGH TEMPERATURES WILL REMAIN COLD AND BELOW AVERAGE FOR
MUCH OF THE NORTH-CENTRAL AND EASTERN U.S. FOLLOWING A FRONTAL
PASSAGE. FORECAST HIGHS RANGE FROM THE TEENS AND 20S FOR THE
NORTHERN PLAINS, GREAT LAKES, AND INTERIOR NORTHEAST; THE 30S AND
40S FOR THE OHIO VALLEY AND MID-ATLANTIC/COASTAL NORTHEAST; AND
THE 50S ACROSS THE SOUTHEAST. CONDITIONS WILL MODERATE CLOSER TO
AVERAGE SATURDAY WITH HIGHS GENERALLY RUNNING 5-15 DEGREES WARMER.
FORECAST HIGHS ARE GENERALLY AT OR ABOVE AVERAGE ACROSS THE WEST,
WITH 40S AND 50S IN THE PACIFIC NORTHWEST, GREAT BASIN, AND
ROCKIES; THE 50S AND 60S IN CALIFORNIA; AND THE 70S IN THE DESERT
SOUTHWEST. CONDITIONS IN THE SOUTHERN PLAINS/TEXAS WILL BE SOME OF
THE WARMEST AND MOST ABOVE AVERAGE COMPARED TO THE REST OF THE
COUNTRY WITH HIGHS INTO THE 60S AND 70S.
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