739
FXUS02 KWBC 280716
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
316 AM EDT MON OCT 28 2024
VALID 12Z THU OCT 31 2024 - 12Z MON NOV 04 2024
..GENERAL OVERVIEW
AN INITIALLY ENERGETIC UPPER TROUGH AND MODERATE SURFACE LOW WILL
LIFT NORTHEASTWARD FROM THE MIDWEST THROUGH THE NORTHEAST
THURSDAY/FRIDAY OVERTOP A WARM AMBIENT UPPER RIDGE OVER THE
EASTERN-SOUTHEASTERN U.S.. AN ASSOCIATED COLD FRONT WILL SWING
THROUGH THE EAST-CENTRAL TO EASTERN U.S. TO FOCUS LINGERING SHOWERS
AND THUNDERSTORMS AND USHER IN MODERATING POST-FRONTAL HIGH
PRESSURE. THE TRAILING PORTION OF THE FRONT IS FORECAST TO
SLOW/DISSIPATE, BUT REMAIN A CONVECTIVE FOCUS TO EMINATE OUT FROM
THE SOUTH-CENTRAL U.S. WITH RETURN FLOW. MEANWHILE UPSTREAM, ROBUST
PACIFIC UPPER TROUGH ENERGY DIGS SHARPLY INTO AN UNSETTLED WEST,
WITH MODERATE RAINS AND SOME ELEVATION SNOWS OVER THE NORTHWEST,
AND MORE SPOTTY ACTIVITY FURTHERN INLAND AND DOWN THE COAST ACROSS
CALIFORNIA. THIS PATTERN MAY LEAD TO CLOSED TROUGH/LOW DEVELOPMENT
NEAR SOUTHERN CALIFORNIA/BAJA. WARM AND AMPLIFIED SUBTROPICAL
RIDGING OVER THE SOUTHEAST MAY PROVE DIFFICULT TO FULLY DISLODGE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
A REDUCTION OF FORECAST SPREAD IN GUIDANCE OVER THE PAST FEW
CYCLES HAS BOLSTERED FORECAST CONFIDENCE THROUGH MEDIUM RANGE TIME
SCALES TO ABOVE NORMAL LEVELS. PREFER A COMPOSITE OF THE LATEST
MODELS AND BEST CLUSTERED ENSEMBLE MEANS OVER TIME ALONG WITH THE
NATIONAL BLEND OF MODELS TO BEST EMPHASIZE THE MOST PREDICTABLE
FORECAST COMPONENTS AT THE EXPENSE OF THE LEAST. THIS SOLUTION,
DESPITE LINGERING ASSOCIATED FORECAST SPREAD, DOES ALLOW LESS
CERTAIN, BUT REASONABLE WEEKEND CLOSED LOW DEVELOPMENT NEAR
SOUTHERN CALIFORNIA/BAJA GIVEN FAVORABLE UPSTREAM UPPER RIDGE
AMPLITUDE. OVERALL, WPC PRODUCT CONTINUITY IS WELL MAINTAINED.
..WEATHER/HAZARDS HIGHLIGHTS
AHEAD OF A SHARPENING FRONT, A LONG FETCH OF RETURN FLOW FROM THE
GULF OF MEXICO APPEARS TO INITIATE AND SUPPORT A LINGERING THREAT
OF MODERATE TO HEAVY RAIN OVER THE LOWER THE MISSISSIPPI VALLEY AND
VICINITY ALONG WITH A POSSIBLE SEVERE WEATHER THREAT HOLDING INTO
THURSDAY. MAINTAINED A WPC EXCESSIVE RAINFALL OUTLOOK MARGINAL RISK
FOR THIS AREA, THOUGH THE ANTECEDENT CONDITIONS ARE QUITE DRY AND
MOST OF THE RAIN WILL HOPEFULLY BE BENEFICIAL.
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 RECENT ECMWF AIFS TRENDS)
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 TO WEST-CENTRAL U.S..
UPPER RIDGING TOGETHER WITH A PRE-FRONTAL LONG FETCH OF STRONG AND
GUSTY SOUTHERLY WINDS WILL TRANSPORT WARMTH FROM THE SOUTH THROUGH
THE NORTHEAST BEFORE MODERATING.
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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