746
FXUS02 KWBC 200655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT SUN OCT 20 2024
VALID 12Z WED OCT 23 2024 - 12Z SUN OCT 27 2024
..GENERAL OVERVIEW
THE WEATHER PATTERN ACROSS THE CONTINENTAL U.S. FOR THE MIDDLE OF
THE WEEK WILL BE FEATURED WITH A SURFACE HIGH OVER THE EASTERN
U.S., ACCOMPANIED BY ABOVE AVERAGE TEMPERATURES AND CONTINUED DRY
CONDITIONS FROM THE MID-ATLANTIC AND THE SOUTHEAST STATES. AN
INCOMING TROUGH FROM THE MIDWEST AND THE ASSOCIATED COLD FRONT WILL
HERALD THE ARRIVAL OF COOLER WEATHER TOWARDS THE END OF THE WEEK,
BUT IT WILL HAVE LIMITED MOISTURE TO WORK WITH SO RAINFALL AMOUNTS
FROM THE GREAT LAKES TO THE NORTHEAST WILL BE GENERALLY LIGHT TO
OCCASIONALLY MODERATE. MEANWHILE, THE NEXT PACIFIC STORM SYSTEM IS
EXPECTED TO APPROACH THE PACIFIC NORTHWEST LATE IN THE WEEK,
BRINGING A RETURN TO RAIN AND HIGH MOUNTAIN SNOW FROM NORTHERN
CALIFORNIA TO WASHINGTON STATE. AN UPPER RIDGE AND MILDER
TEMPERATURES ARE LIKELY AHEAD OF THIS PACIFIC STORM SYSTEM ACROSS
MUCH OF THE CENTRAL U.S.
..GUIDANCE/PREDICTABILITY ASSESSMENT
IT REMAINS THE CASE THAT MODEL SPREAD IS HIGHER THAN USUAL
THROUGHOUT THE ENTIRE FORECAST PERIOD, AND THUS BELOW AVERAGE
CONFIDENCE IN FORECAST SPECIFICS. THE MODELS ARE STILL STRUGGLING
WITH THE FLOW PATTERN ACROSS THE EASTERN PACIFIC AND INTO THE
PACIFIC NORTHWEST, AND THIS IN TURN AFFECTS THE AMPLITUDE AND
POSITION OF BOTH UPPER RIDGE OVER THE ROCKIES AND WESTERN HIGH
PLAINS, AND ALSO THE EVOLVING CLOSED LOW OFF THE NORTHWEST COAST
AND ITS EVENTUAL EVOLUTION AS IT TRACKS INLAND. CHANGES IN FUTURE
FORECASTS ARE A NEAR CERTAINTY AS THE WEATHER PATTERN COMES INTO
BETTER FOCUS IN FUTURE MODEL RUNS.
UPON EXAMINATION OF THE AVAILABLE GUIDANCE, THE GFS AND GEFS MEAN,
AND TO A SLIGHTLY LESSER EXTENT THE CMC, WERE GENERALLY IN BETTER
AGREEMENT WITH THE ML GUIDANCE FROM THE ECMWF, WHICH DIFFERED IN
MANY AREAS FROM THE OPERATIONAL ECMWF. THE GFS BASED GUIDANCE
APPEARED TO HAVE A BETTER OVERALL HANDLE ON THE FORECAST EVOLUTION,
SO THE FORECAST WAS HEDGED MORE IN THAT DIRECTION. SOME PREVIOUS
WPC CONTINUITY WAS ALSO USED FOR DAYS 3 THROUGH 6. THE GEFS AND
NAEFS ACCOUNTED FOR ABOUT 60-70% OF THE FORECAST BLEND BY NEXT
WEEKEND AMID THE HIGH MODEL SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
THE COLD FRONT CROSSING THE GREAT LAKES AND INTO THE NORTHEAST
WEDNESDAY INTO EARLY THURSDAY WILL LIKELY HAVE JUST ENOUGH
MOISTURE AND LIFT TO PRODUCE SOME MAINLY LIGHT TO MODERATE SHOWERS,
MAINLY NORTH OF THE INTERSTATE 70 CORRIDOR. IT SHOULD CONTINUE TO
REMAIN DRY AND MOSTLY SUNNY FOR AREAS FARTHER TO THE SOUTH ACROSS
THE MID-ATLANTIC AND THE SOUTHEAST U.S., WHERE THE VERY PLEASANT
FALL WEATHER WILL CONTINUE FOR A WHILE. THERE ARE CURRENTLY NO
RISK AREAS IN THE DAY 4 AND DAY 5 EXCESSIVE RAINFALL OUTLOOKS.
THE PATTERN WILL BECOME FAVORABLE FOR THE RETURN OF PRECIPITATION
TO THE PACIFIC NORTHWEST LATE THIS WEEK INTO THE WEEKEND. HOWEVER
THERE IS CONTINUED MODEL SPREAD FOR A SYSTEM EXPECTED TO DEVELOP
OVER THE EASTERN PACIFIC BY MIDWEEK AND LIFT NORTHEASTWARD
THEREAFTER. RAIN AND HIGH ELEVATION NORTHERN CASCADES SNOW COULD
COMMENCE AS EARLY AS LATE THURSDAY PER THE FAST SIDE OF THE SPREAD,
OR TAKE UNTIL LATE FRIDAY OR SO ON THE SLOWER SIDE. CURRENTLY
THIS LOOKS MORE LIKE A BROAD PRECIPITATION EVENT RATHER THAN A
FOCUSED ATMOSPHERIC RIVER, BUT SOME LOCALLY ENHANCED TOTALS WILL BE
POSSIBLE. LIGHTER PRECIPITATION IS FORECAST TO REACH THE NORTHERN
ROCKIES BY THE WEEKEND.
TEMPERATURES WILL FEEL MORE LIKE SEPTEMBER ACROSS AREAS FROM THE
CENTRAL U.S. INTO THE NORTHEAST MID-WEEK, WITH HIGHS RUNNING 10-20
DEGREES ABOVE AVERAGE FOR LATE OCTOBER AND POSSIBLY EVEN A LITTLE
HIGHER OVER PARTS OF THE UPPER MIDWEST/NORTHERN GREAT LAKES ON
TUESDAY. A COLD FRONT PUSHING RAPIDLY EASTWARD FROM THE NORTHERN
PLAINS WILL BRING A RETURN TO MORE SEASONABLE CONDITIONS FOR THE
END OF THE WEEK. FROM LATE WEEK INTO THE WEEKEND, A BUILDING
WESTERN U.S. UPPER RIDGE THAT PUSHES EASTWARD AHEAD OF THE PACIFIC
STORM SYSTEM SHOULD PROMOTE A WARMING TREND FIRST OVER THE
INTERMOUNTAIN WEST AND ROCKIES/WESTERN HIGH PLAINS, AND THEN
COVERING MUCH OF THE CENTRAL U.S. WHERE MANY AREAS SHOULD SEE HIGHS
ON THE ORDER OF 10-20 DEGREES ABOVE NORMAL.
HAMRICK
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM
RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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