841
FXUS01 KWBC 200801
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EST WED NOV 20 2024
VALID 12Z WED NOV 20 2024 - 12Z FRI NOV 22 2024
...BACK-TO-BACK POWERFUL PACIFIC STORM SYSTEMS TO IMPACT THE WEST
COAST THROUGH THE END OF THIS WEEK WITH HEAVY RAIN,
LIFE-THREATENING FLOODING, STRONG WINDS, AND HIGHER ELEVATION
MOUNTAIN SNOW...
...NEAR BLIZZARD CONDITIONS ARE POSSIBLE THROUGH THIS EVENING
ACROSS THE NORTHERN PLAINS...
...HEAVY SNOW IS LIKELY THROUGHOUT PARTS OF THE CENTRAL
APPALACHIANS BEGINNING ON THURSDAY, WITH A SEPARATE BURST OF
SNOWFALL POSSIBLE ACROSS NORTHEAST PENNSYLVANIA AND NEIGHBORING
REGIONS OF THE NORTHEAST THURSDAY NIGHT INTO FRIDAY...
THE ACTIVE NOVEMBER WEATHER PATTERN IMPACTING CONUS IS FORECAST TO
CONTINUE THROUGH THE END OF THIS WEEK AND BRING HAZARDOUS RAIN,
WIND, AND SNOW FOR SEVERAL REGIONS. A SIGNIFICANT PACIFIC STORM
SYSTEM AND STRONG ATMOSPHERIC RIVER HAVE ALREADY STARTED PUMMELING
THE WEST COAST AND NORTHWEST THIS MORNING. THE VERY DEEP LOW
PRESSURE SYSTEM CHURNING ABOUT 300 MILES OFF THE COAST OF
WASHINGTON IS RESPONSIBLE FOR HIGH WINDS IMPACTING MUCH OF
NORTHERN CALIFORNIA, OREGON, AND WASHINGTON. THESE WINDS HAVE
ALREADY PRODUCED NUMEROUS POWER OUTAGES, REPORTS OF TREE DAMAGE,
AND ARE EXPECTED TO CREATE BLIZZARD CONDITIONS THROUGHOUT THE
CASCADES. FORTUNATELY THESE WINDS ARE EXPECTED TO GRADUALLY
SUBSIDE BY MIDDAY AS THE LOW PRESSURE SYSTEM SWINGS AWAY FROM THE
REGION. HOWEVER, A CONTINUOUS PLUME OF AMPLE ATMOSPHERIC MOISTURE
CONTENT ENTERING NORTHERN CALIFORNIA THIS MORNING IS FORECAST TO
LINGER THROUGH THE END OF THE WEEK AND LEAD TO EXTREME RAINFALL
TOTALS. OVER 10 INCHES OF RAINFALL ACROSS THE NORTHERN CALIFORNIA
COAST AND INLAND MOUNTAIN RANGES ARE LIKELY TO INCREASE THE THREAT
OF LIFE-THREATENING FLASH FLOODING, ROCK SLIDES, AND DEBRIS FLOWS.
AS THIS CORRIDOR OF HEAVY RAINFALL LINGERS ALONG A STATIONARY
BOUNDARY EXTENDING INTO THE PACIFIC OCEAN, A SEPARATE AREA OF LOW
PRESSURE IS FORECAST TO DEVELOP AND RAPIDLY STRENGTHEN OFF THE
NORTHWEST COAST ON FRIDAY. THIS STORM WILL HELP AMPLIFY THE
ATMOSPHERIC RIVER STREAMING INTO NORTHERN CALIFORNIA THROUGH
FRIDAY MORNING, EXACERBATING THE FLOODING THREAT. WPC HAS ISSUED A
HIGH RISK (LEVEL 4/4) OF EXCESSIVE RAINFALL ON THURSDAY IN ORDER
TO FURTHER HIGHLIGHT THIS CONCERN. ADDITIONALLY, ANOTHER ROUND OF
STRONG WINDS ARE ANTICIPATED FROM THIS SECOND LOW PRESSURE SYSTEM
THROUGHOUT THE NORTHWEST TO END THE WEEK. RESIDENTS AND VISITORS
RESIDING OR TRAVELING BETWEEN NORTHERN CALIFORNIA AND WASHINGTON
ARE ADVISED TO CHECK ROAD CONDITIONS BEFORE VENTURING OUT, LISTEN
TO ADVICE FROM LOCAL OFFICIALS, REVIEW EMERGENCY PLANS, AND HAVE
MULTIPLE WAYS OF RECEIVING WARNINGS.
FOR THE CENTRAL U.S. THE MAIN WEATHER STORY WILL BE FOUND
THROUGHOUT THE NORTHERN PLAINS AS HEAVY SNOW AND GUSTY WINDS
CREATE NEAR BLIZZARD CONDITIONS TODAY. THESE HAZARDOUS WEATHER
CONDITIONS ARE RESULTING FROM A SLOW-MOVING AND GRADUALLY
WEAKENING LOW PRESSURE SYSTEM JUST NORTH OF THE MINNESOTA-NORTH
DAKOTA BORDER. THE GREATEST SNOWFALL AMOUNTS ARE FORECAST ACROSS
NORTH DAKOTA, EASTERN SOUTH DAKOTA, AND NORTHWEST MINNESOTA, BUT
WITH ADDITIONAL TOTALS TODAY GENERALLY UNDER 4 INCHES. WIND
IMPACTS SHOULD BE MORE WIDESPREAD AND EXTEND INTO EASTERN MONTANA
AND NEBRASKA AS MAXIMUM GUSTS COULD EXCEED 60 MPH THROUGH TONIGHT.
THIS AREA OF LOW PRESSURE IS ANTICIPATED TO RAPIDLY WEAKEN TONIGHT
AND LEAD TO CALMER CONDITIONS ON THURSDAY.
AFTER AN EXTENDED PERIOD OF DRY AND TRANQUIL WEATHER ACROSS THE
NORTHEAST, THE UPPER LEVEL SYSTEM EXITING THE NORTHERN PLAINS
TODAY WILL SLIDE EASTWARD AND PRODUCE A CHANCE FOR HEAVY
PRECIPITATION IN THE FORM OF BOTH RAIN AND SNOW. THE EVOLUTION OF
SURFACE FEATURES OVER THE NEXT FEW DAYS ARE FORECAST TO BEGIN WITH
A DEVELOPING STRONG AND COMPACT LOW PRESSURE SYSTEM OVER THE GREAT
LAKES TODAY, WHILE A COLD FRONT QUICKLY PUSHES EASTWARD TO THE
MID-ATLANTIC BY TONIGHT. SHOWERS AND MAYBE A RUMBLE OF THUNDER MAY
ACCOMPANY THIS COLD FRONT AS RAIN POSSIBLY MIXES WITH SNOW
SPREADING ACROSS THE GREAT LAKES. BY THURSDAY, A SEPARATE AREA OF
LOW PRESSURE FORMING ALONG THE AFOREMENTIONED COLD FRONT IS
EXPECTED TO DEEPEN AND LIFT NORTHWARD INTO THE NORTHEAST, WHILE
ALSO LEADING TO A BLOSSOMING PRECIPITATION SHIELD. RAIN IS MOST
LIKELY ACROSS NEW ENGLAND WHERE WARMER AIR SURGES FROM THE
ATLANTIC OCEAN, BUT THE HIGHER ELEVATIONS AND AREA DIRECTLY
UNDERNEATH THE COLD UPPER LOW PRESSURE SYSTEM MAY SEE
PRECIPITATION FALL AS HEAVY SNOW. PROBABILITIES FOR AT LEAST 4
INCHES OF SNOW BY FRIDAY NIGHT ARE HIGH (70-90%) ACROSS NORTHEAST
PENNSYLVANIA AND THE SOUTHERN CATSKILL MOUNTAINS OF NEW YORK.
IMPACTFUL SNOWFALL IS ALSO LIKELY TO BE EXPERIENCED THROUGHOUT THE
ALLEGHENY MOUNTAINS OF WEST VIRGINIA, MARYLAND, AND PENNSYLVANIA
THROUGH THE END OF THE WEEK DUE TO A LONGER DURATION FAVORABLE
UPSLOPE SNOW SETUP. TOTAL SNOWFALL AMOUNTS IN THESE HIGHER
ELEVATIONS COULD ADD UP TO A FOOT.
ELSEWHERE, HIGH PRESSURE BUILDING INTO THE SOUTH-CENTRAL U.S. WILL
CREATE DRY CONDITIONS FROM THE LOWER MISSISSIPPI VALLEY TO MUCH OF
THE PLAINS, ROCKIES, AND SOUTHWEST. THE TEMPERATURE OUTLOOK
FEATURES ONE FINAL DAY OF WIDESPREAD 60S AND 70S ALONG THE EAST
COAST BEFORE A STRONG COLD FRONT KNOCKS AFTERNOON HIGHS BELOW
AVERAGE THROUGH THE START OF THE WEEKEND. THE COLDEST TEMPERATURES
WHEN COMPARED TO CLIMATOLOGY OVER THE NEXT FEW DAYS ARE FORECAST
ACROSS THE NORTHERN PLAINS (HIGHS IN THE 20S) AND OHIO VALLEY
(HIGHS IN THE 30S AND 40S).
SNELL
GRAPHICS AVAILABLE AT
HTTPS://WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP
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