065
FXUS02 KWBC 010658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT TUE OCT 1 2024
VALID 12Z FRI OCT 04 2024 - 12Z TUE OCT 08 2024
..OVERVIEW
FOR THE FRIDAY-TUESDAY PERIOD, LATEST MODELS AND ENSEMBLES
CONTINUE TO SHOW A PATTERN TRANSITION FROM PROGRESSIVE NORTHERN
TIER FLOW TOWARD AN AMPLIFYING EASTERN U.S./ATLANTIC COAST TROUGH
WHILE A MEAN RIDGE COVERING MUCH OF THE WEST EXTENDS INTO THE
PLAINS, PRODUCING AN EXTENDED PERIOD OF UNSEASONABLY WARM TO HOT
WEATHER. SEPARATE FRONTS AFFECTING THE NORTHEAST AND NORTHWEST
LATE THIS WEEK SHOULD GENERATE MAINLY LIGHT RAIN, BUT THE FRONT
AND POTENTIAL EMBEDDED SURFACE SYSTEM REACHING NEAR THE EAST COAST
NEXT WEEK COULD SUPPORT MORE ORGANIZED RAINFALL OVER THAT REGION.
FARTHER SOUTH, NOT MUCH HAS CHANGED REGARDING THE OVERALL FORECAST
EVOLUTION FAVORING LOW PRESSURE AND HEAVY RAINFALL POTENTIAL OVER
THE GULF OF MEXICO WITH SOME POCKETS OF ENHANCED MOISTURE POSSIBLY
EXTENDING INTO SOME AREAS ALONG THE GULF COAST, BUT WITH POOR
AGREEMENT/CONSISTENCY FOR DETAILS. THERE MAY BE MULTIPLE SURFACE
FEATURES TO FOCUS RAINFALL, INCLUDING ONE LIFTING FROM THE
NORTHWESTERN CARIBBEAN INTO THE GULF AND ANOTHER THAT MAY BE OVER
THE WESTERN GULF.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE AGREEMENT FOR NORTHERN STREAM FLOW LATE THIS WEEK INTO
THE WEEKEND HAS BEEN INCREMENTALLY IMPROVING, WITH FAIRLY STRONG
CLUSTERING AMONG MOST DYNAMICAL MODEL/ENSEMBLE SOLUTIONS OVER THE
PAST DAY BUT WITH A LINGERING STRAY SOLUTION OR TWO. FOR EXAMPLE,
THE 18Z GFS WAS A BIT ON THE SLOW SIDE WITH THE UPPER SHORTWAVE
PROGRESSING FROM THE EAST PACIFIC INTO THE UPPER MIDWEST, WHILE BY
SUNDAY THE THE NEW 00Z CMC CLOSES OFF AN EMBEDDED LOW IN A WAY NOT
DEPICTED IN OTHER GUIDANCE. TROUGH DETAILS BECOME MORE OF A
QUESTION MARK TOWARD THE EAST COAST BY NEXT MONDAY-TUESDAY. ECMWF
RUNS HAVE CONSISTENTLY CLOSING OFF AN UPPER LOW AROUND NEW ENGLAND
AND THE PREVIOUSLY OPEN GFS NOW SHOWS A CLOSED LOW IN THE 00Z RUN.
MACHINE LEARNING (ML) MODELS AND THE ECMWF AIFS MEAN KEEP THE
TROUGH MORE OPEN LIKE THE ENSEMBLE MEANS, THOUGH THE 00Z GEFS/12Z
ECENS MEANS EVENTUALLY IMPLY AN UPPER LOW OVER THE CANADIAN
MARITIMES AFTER TUESDAY. IN SPITE OF THE MORE OPEN UPPER TROUGH,
THE ML MODELS DO OFFER SOME SIGNAL FOR A SURFACE WAVE NEAR NEW
ENGLAND, JUST IN LESS PRONOUNCED FORM THAN THE SOLUTIONS WITH A
CLOSED UPPER LOW. ALSO WORTH KEEPING AN EYE ON, BY TUESDAY SOME ML
MODELS SHOW MORE POTENTIAL FOR A SHORTWAVE FROM HUDSON BAY
SOUTH/SOUTHWESTWARD VERSUS WHAT MOST DYNAMICAL GUIDANCE SHOWS.
THE FORECAST OVER AND NEAR THE GULF OF MEXICO CONTINUES TO HAVE LOW
PREDICTABILITY DUE TO A COMBINATION OF SMALLER-SCALE FEATURES. ONE
WAVE MAY TRACK INTO THE CENTRAL/EAST-CENTRAL GULF FROM THE
NORTHWESTERN CARIBBEAN WHILE ANOTHER FEATURE MAY EVOLVE OVER THE
WESTERN GULF, WITH THE SURFACE/QPF DETAILS ALSO POTENTIALLY
AFFECTED BY ENERGY ALOFT OVER TEXAS AND NEARBY AREAS. AS FOR THE
LATTER, THE 00Z GFS IS A NOTABLY STRONG SOLUTION WITH ITS UPPER
FEATURE OVER TEXAS. MINUS THE 12Z CMC WHICH WAS VERY FAST WITH ITS
CARIBBEAN/EASTERN GULF SYSTEM (AS SOME EARLIER RUNS WERE), RECENT
TRENDS IN GUIDANCE OVERALL HAVE BEEN TO HOLD LOW PRESSURE OVER THE
GULF FOR A LONGER TIME BEFORE IT TRACKS EASTWARD TOWARD FLORIDA.
SOME NEW 00Z SOLUTIONS ARE STILL OVER THE CENTRAL GULF BY NEXT
TUESDAY. THE UPDATED FORECAST REFLECTS WPC/NHC COORDINATED
CONTINUITY OVER THE WESTERN GULF WITH A TROUGH, AND CLOSE TO
CONTINUITY WITH THE SPOT LOW OVER THE CENTRAL/EASTERN GULF.
CONTINUE TO MONITOR OUTLOOKS FROM THE NATIONAL HURRICANE
CENTER FOR THE LATEST INFORMATION ON FEATURES OF INTEREST.
FOR THE MOST PART, AN OPERATIONAL MODEL BLEND SUFFICED FOR THE
EARLY PART OF THE FORECAST. THE 18Z GFS COMPONENT WAS SPLIT WITH
THE GEFS MEAN DUE TO THE FORMER BEING SLOW WITH THE NORTHERN TIER
PACIFIC SHORTWAVE. BY MID-LATE PERIOD, THE 12Z CMC WAS REMOVED DUE
TO ITS NONCONFORMING GULF SYSTEM WHILE THE BLEND TRANSITIONED
TOWARD A BLEND OF THE 18Z GFS/12Z ECMWF AND THEIR ENSEMBLE MEANS
DUE TO DECREASING CONFIDENCE IN DETAIL SPECIFICS.
..WEATHER/HAZARDS HIGHLIGHTS
VERY LITTLE HAS CHANGED OVER THE PAST DAY IN TERMS OF THE LOW
CONFIDENCE FOR WHERE AREAS OF HEAVY RAIN COULD EXTEND INTO SOME
COASTAL/INLAND AREAS NEAR THE GULF COAST DURING THE PERIOD. FOR THE
FRIDAY-SATURDAY TIME FRAME COVERED BY THE DAYS 4-5 EXCESSIVE
RAINFALL OUTLOOKS, THERE ARE MINORITY MODEL SOLUTIONS
SHOWING POCKETS OF ENHANCED RAINFALL ALONG PARTS OF THE
CENTRAL/EAST-CENTRAL GULF COAST AND/OR THE TEXAS COAST. HOWEVER
WHILE SEPARATE ENSEMBLE SYSTEMS DIFFER OVER WHERE THE BEST HEAVY
RAIN POTENTIAL WILL BE OVER THE GULF, THEY DO NOT EXTEND THEIR
BETTER PROBABILITIES TO LAND. THE COMBINATION OF POOR GUIDANCE
CLUSTERING/CONTINUITY AND HIGH FLASH FLOOD GUIDANCE VALUES ALONG
THE GULF COAST REGION CONTINUE TO FAVOR NOT DEPICTING ANY RISK
AREAS ON THE DAYS 4-5 EROS. RECENT GUIDANCE HAS BEEN SUGGESTING
THAT SOME HEAVY RAIN MAY EVENTUALLY SPREAD ACROSS FLORIDA BY EARLY
NEXT WEEK, PERHAPS AIDED BY A FRONT APPROACHING FROM THE NORTH.
FROM FRIDAY THROUGH THE WEEKEND, EXPECT LIGHTER RAINFALL ALONG
PORTIONS OF THE FRONTS SUPPORTED BY NORTHERN STREAM DYNAMICS. ONE
FRONT MAY PRODUCE AREAS OF LIGHT RAIN OVER THE NORTHEAST LATE THIS
WEEK WHILE A FRONT REACHING THE PACIFIC NORTHWEST AROUND FRIDAY
MAY PRODUCE SOME LIGHT RAIN AS WELL. A FRONTAL SYSTEM AND POSSIBLE
DEVELOPING EMBEDDED LOW MAY PRODUCE MORE ORGANIZED RAINFALL TOWARD
THE EAST COAST BY NEXT MONDAY-TUESDAY. COVERAGE AND MAGNITUDE WILL
DEPEND ON SYSTEM SPECIFICS THAT HAVE LOWER CONFIDENCE AT THIS TIME.
AN APPROACHING PACIFIC FRONT MAY BRING LIGHT RAIN TO THE NORTHERN
PACIFIC NORTHWEST EARLY NEXT WEEK.
THE STRONG AND PERSISTENT UPPER RIDGE COVERING THE WEST AND
EXTENDING INTO THE PLAINS WILL SUPPORT A LENGTHY PERIOD OF WELL
ABOVE NORMAL TEMPERATURES OVER MAY PARTS OF THE WESTERN/CENTRAL
U.S. HIGHS 10-20F OR SO ABOVE NORMAL WILL BE COMMON AND NUMEROUS
DAILY RECORDS APPEAR LIKELY FROM THE SOUTHERN HALF OF THE WEST
INTO PARTS OF THE HIGH PLAINS, ESPECIALLY FRIDAY-SUNDAY. EASTERN
U.S. TEMPERATURES WILL VARY IN THE NEAR TO ABOVE NORMAL RANGE UNTIL
THE EAST COAST TROUGH DROPS SOME HIGHS MODERATELY BELOW NORMAL NEXT
TUESDAY.
RAUSCH
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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