148
FXUS02 KWBC 271857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT SUN OCT 27 2024
VALID 12Z WED OCT 30 2024 - 12Z SUN NOV 03 2024
...SEVERE WEATHER POSSIBLE WEDNESDAY WITH AN ISOLATED HEAVY RAIN
THREAT OVER PARTS OF THE CENTRAL/SOUTHERN PLAINS INTO THE MID-
MISSISSIPPI VALLEY...
..GENERAL OVERVIEW
AN AMPLIFIED UPPER TROUGH WILL EJECT OVER THE CENTRAL U.S. MIDWEEK
BEFORE LIFTING INTO/OVERTOP A WARM AMBIENT UPPER RIDGE OVER THE
EASTERN-SOUTHEASTERN U.S.. THIS WILL RESULT IN A WAVY AND SHARP
FRONT THROUGH THE MID-SECTION OF THE COUNTRY WHERE A COUPLE ROUNDS
OF MODERATELY HEAVY RAIN ARE FORECAST FROM THE EASTERN PLAINS
THROUGH THE MISSISSIPPI VALLEY AND MIDWEST MID-LATER THIS WEEK AND
INTO NEXT WEEKEND. THE TRAILING PORTION OF THE FRONT IS FORECAST TO
SLOW/DISSIPATE IN RESPONSE TO ROBUST RENEWED TROUGH ENERGY DIGGING
OUT OF THE NORTHEAST PACIFIC AND INTO THE WEST/SOUTHWEST.
SUBTROPICAL RIDGING OVER THE SOUTHEAST WILL MAINTAIN MILD/WARM
TEMPERATURES FOR MUCH OF THE LOWER 48 EAST OF THE ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODELS/ENSEMBLES SHOWED GOOD AGREEMENT THROUGH MOST OF THE
FORECAST PERIOD THOUGH THE 00Z CANADIAN/UKMET WERE DISPLACED FROM
THE BETTER CLUSTERING OF THE 06Z GFS/00Z ECMWF WITH THEIR ENSEMBLE
MEANS (AND 00Z NAEFS MEAN). USED A BLEND OF THE GFS/ECMWF FOR MUCH
OF THE FORECAST PERIOD WHICH MAINTAINED GOOD CONTINUITY. BY NEXT
WEEKEND, THE FLOW OVER THE PACIFIC AND INTO THE WEST REMAINS QUITE
UNCERTAIN DUE TO SOME VIGOROUS FEATURES IN THE MID-LATITUDES AS
WELL AS THE LIKELY FUTURE EXTRATROPICAL TRANSITION OF WHAT IS
CURRENTLY TROPICAL STORM 23W (KONG-REY). THOUGH NOT EVERY RECURVING
W PAC TROPICAL SYSTEM AMPLIFIES THE DOWNSTREAM FLOW INTO NOAM, THE
OVERALL PATTERN SEEMS QUITE ACTIVE AND THE MACHINE LEARNING MODELS
HAVE GENERALLY FAVORED A MORE AMPLIFIED AND SLOWER PATTERN BY NEXT
WEEKEND INTO THE SOUTHWEST. THOUGH CERTAINLY POSSIBLE, STUCK WITH
A FULLY ENSEMBLE MEAN-DRIVEN SOLUTION FOR NEXT SUNDAY THAT WAS JUST
A BIT QUICKER THAN THE ENSEMBLE MEANS BUT CURIOUSLY SLOWER THAN
THE DETERMINISTIC MODELS (WHICH ARE NOT TYPICALLY FASTER THAN THE
ENSEMBLE MEANS IN THESE CASES).
..WEATHER/HAZARDS HIGHLIGHTS
AHEAD OF A SHARPENING FRONT, A LONG FETCH OF RETURN FLOW FROM THE
GULF OF MEXICO APPEARS TO INITIATE AND SUPPORT AN ISOLATED AND LOW-
END THREAT OF MODERATE TO PERHAPS HEAVY RAIN FROM THE
CENTRAL/SOUTHERN PLAINS THROUGH THE MISSISSIPPI VALLEY AMID A
SEVERE WEATHER THREAT WEDNESDAY AND PERHAPS INTO THURSDAY.
MAINTAINED THE MARGINAL RISK IN THE ERO FOR THESE AREAS THOUGH THE
ANTECEDENT CONDITIONS ARE QUITE DRY AND MOST OF THE RAIN WILL BE
BENEFICIAL.
COOLING TEMPS MAY LEAD TO NEW AREAS OF FROST/FREEZE POTENTIAL BACK
IN THE POST-FRONTAL AIRMASS INTO MIDWEEK. THE TRAILING PORTION OF
THE FRONT IS THEN FORECAST TO STALL OVER THE SOUTHERN PLAINS WHERE
MODERATE TO HEAVY RAINFALL COULD LINGER AND THEN EXPAND
NORTHEASTWARD BY NEXT WEEKEND AS ROBUST UPPER TROUGH/CLOSED LOW
ENERGY DIGS UPSTREAM INTO THE WEST COAST TO RE-AMPLIFY THE FLOW
OVER THE LOWER 48 AND VICINITY. PRECIPITATION ASSOCIATED WITH THE
NEXT PACIFIC SYSTEM AND LONG-FETCH MOISTURE IS FORECAST TO RE-
FOCUS INTO THE WEST COAST LATER IN THE WEEK AND INTO NEXT WEEKEND,
WITH HIGH-ELEVATION SNOW REACHING INTO THE NORTHERN ROCKIES AND
MODEST RAINS REACHING DOWN THROUGH CALIFORNIA. HERE, RAINFALL COULD
BE HEAVIER (PER THE ECMWF AIFS) SHOULD A SLOWER/STRONGER SOLUTION
VERIFY. REGARDLESS, THE COLD FRONTAL SURGE AND POSSIBLE CLOSED LOW
DEVELOPMENT AT THE SOUTHERN BASE OF THE MAIN UPPER TROUGH WILL
BRING IN COOLER TEMPERATURES TO MUCH OF THE WEST.
UPPER RIDGING TOGETHER WITH A PRE-FRONTAL LONG FETCH OF STRONG AND
GUSTY SOUTHERLY WINDS WILL TRANSPORT WARMTH FROM THE SOUTH THROUGH
THE NORTHEAST THIS PERIOD. HIGH TEMPERATURES WILL THREATEN NEW
DAILY RECORD HIGH TEMPERATURES WED/THU FROM TX NORTHEASTWARD BEFORE
MODERATING.
FRACASSO/SCHICHTEL
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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