995
FXUS02 KWBC 071905
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
305 PM EDT SAT SEP 7 2024
VALID 12Z TUE SEP 10 2024 - 12Z SAT SEP 14 2024
...MULTI-DAY WESTERN TO CENTRAL GULF COAST STATES HEAVY
RAINFALL/FLOODING THREAT THROUGH EARLY-MID NEXT WEEK, WITH
POSSIBLE TROPICAL SYSTEM DEVELOPMENT BEING MONITORED BY NHC...
..OVERVIEW
WIDESPREAD AND PROTRACTED HEAVY RAIN/THUNDERSTORMS WITH FLOODING
ISSUES WILL MAKE WEATHER HEADLINES FOR THE WESTERN TO CENTRAL GULF
COAST STATES WITH INLAND RETURN RESURGENCE OF DEEP GULF MOISTURE
WITH A SLOWLY LIFTING WARM FRONT EARLY TO MID-LATER NEXT WEEK.
THIS THREAT COULD BE SIGNIFICANTLY ENHANCED WITH POSSIBLE TROPICAL
SYSTEM DEVELOPMENT AND APPROACH AS CURRENTLY MONITORED BY NHC.
ELSEWHERE, IT GENERALLY REMAINS THE CASE THAT THE BEGINNING OF
NEXT WEEK WILL BE FEATURED WITH AN UPPER LEVEL TROUGH EXITING THE
NORTHEAST U.S. AND A LARGE SURFACE HIGH. THE INITIALLY FALL-LIKE
AIRMASS WILL UNDERGO A MODERATION TREND GOING INTO THE MIDDLE TO
END OF THE WEEK WITH WIDESPREAD 80S FOR HIGHS RETURNING. OUT WEST,
THE PERSISTENT UPPER RIDGE AND WIDESPREAD ANOMALOUS WARMTH IS
FORECAST TO ABATE FOR THE SECOND HALF OF NEXT WEEK AS AN UPPER
TROUGH AND LIGHT TO MODERATE PRECIPITATION FOCUS WORKS ACROSS THE
WEST COAST, THE INTERMOUNTAIN WEST AND THEN EVENTUALLY OUT THROUGH
THE NORTHERN ROCKIES/PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL GUIDANCE STILL FEATURES GOOD OVERALL SYNOPTIC SCALE
AGREEMENT ACROSS THE NATION INTO TUESDAY/WEDNESDAY, WITH
DIFFERENCES SLOWLY INCREASING THROUGH LONGER TIME FRAMES. GUIDANCE
HAS SHOWN MEASURED CYCLE TO CYCLE UNCERTAINTY WITH THE AMPLIFYING
TROUGH OVER THE NORTHWESTERN U.S., BUT A FAVORED COMPOSITE HAS
TRENDED TOWARD THE MORE AMPLIFIED SIDE OF THE FULL ENVELOPE OF
SOLUTIONS. IMPORTANTLY, THE FORECAST SIGNAL CONTINUES TO INCREASE
IN FAVOR OF POSSIBLE TROPICAL SYSTEM DEVELOPMENT OVER THE GULF OF
MEXICO WITH LIKELY IMPACTS FOR THE WESTERN TO CENTRAL GULF COAST.
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A 00
UTC ECMWF/NAEFS ENSEMBLE MEAN BLEND ALONG WITH THE 13 UTC NATIONAL
BLEND OF MODELS AND WPC OVERNIGHT CONTINUITY. THIS SOLUTION WORKS
WELL WITH LATEST NHC GUIDANCE AND ALSO HAS GOOD COMPOSITE MODEL
SUPPORT OVER MUCH OF THE REST OF THE COUNTRY FOR NEXT WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
INCREASING TROPICAL MOISTURE OVER THE SOUTHWESTERN GULF OF
MEXICO/BAY OF CAMPECHE IN THE SHORT TERM IS EXPECTED TO BRING AN
INCREASING THREAT FOR HEAVY RAIN AND STRONG STORMS TO THE COASTAL
AREAS OF THE GULF COAST STATES THROUGH NEXT WEEK. THIS DISTURBANCE
IS ALSO BEING MONITORED BY THE NATIONAL HURRICANE CENTER FOR
POSSIBLE DEVELOPMENT OF A TROPICAL DEPRESSION OR STORM AS THE
SYSTEM GETS CLOSER TO THE TEXAS COAST. FOR THE DAY 4 PERIOD
TUESDAY, THE GUIDANCE GENERALLY KEEPS THE HEAVIEST RAIN CLOSE TO
THE COAST OR JUST OFFSHORE THE TEXAS COAST. OWING TO WET ANTECEDENT
CONDITIONS FROM HEAVY RAIN IN THE DAYS LEADING UP TO THIS, A
SLIGHT RISK REMAINS VALID FROM SOUTH TEXAS TO NEAR LAKE CHARLES,
WHERE A MULTIPLE INCHES OF RAINFALL WILL BE POSSIBLE FOR SOME OF
THESE AREAS. GOING INTO THE DAY 5 PERIOD WEDNESDAY, THERE IS A
DECENT OVERALL MODEL SIGNAL FOR A SWATH OF ENHANCED RAINFALL MOVING INLAND
ACROSS SOUTHEAST TEXAS AND INTO CENTRAL LOUISIANA, WITH
POTENTIALLY A SHARP WESTERN GRADIENT OF THE QPF INLAND FROM THE TEXAS
GULF COAST. A SLIGHT RISK REMAINS FROM THE CENTAL TEXAS COAST TO
NEAR BATON ROUGE. A MODERATE RISK UPGRADE WAS CONSIDERED AND MAY
BE NEEDED PENDING FUTURE NHC UPDATES.
OTHERWISE, THE TROUGH ARRIVING OVER THE WEST WILL LIKELY PRODUCE
MAINLY LIGHT TO MODERATE SHOWERS ACROSS PORTIONS OF THE PACIFIC
NORTHWEST AND INTO THE ROCKIES THROUGH THURSDAY NIGHT. THE HEAVIEST
QPF FROM THIS WILL LIKELY BE OVER NORTHERN WYOMING AND INTO
MONTANA, WITH SNOW FOR THE HIGHEST MOUNTAIN RIDGES. SHOWERS AND
SOME STORMS THEN REACH THE CENTRAL/NORTHERN PLAINS BY FRIDAY, WHILE
THE NORTHEASTERN QUADRANT OF THE NATION REMAINS DRY.
TEMPERATURES ARE EXPECTED TO BE UNSEASONABLY WARM BY SEPTEMBER
STANDARDS ACROSS MUCH OF THE NORTH-CENTRAL U.S., WITH HIGHS
RUNNING ABOUT 5 TO 15 DEGREES ABOVE AVERAGE FROM THE FRONT RANGE OF
THE ROCKIES TO THE WESTERN GREAT LAKES FOR MUCH OF THE WEEK. THE
HOT WEATHER EXPECTED ACROSS MUCH OF THE WEST COAST AND
INTERMOUNTAIN WEST DURING THE SHORT RANGE PERIOD IS EXPECTED TO
IMPROVE GOING INTO THE MIDDLE OF NEXT WEEK AS THE UPPER TROUGH
BUILDS SOUTHWARD AND HERALDS THE ARRIVAL OF A COLD FRONT, BRINGING
TEMPERATURES OF 5 TO 15 DEGREES BELOW NORMAL FOR PORTIONS OF THE
WEST COAST STATES AND INTO NEVADA. SLIGHTLY BELOW AVERAGE READINGS
ARE ALSO LIKELY FOR THE GULF COAST REGION (BUT STILL HUMID) OWING
TO INCREASED CLOUD COVER AND RAIN.
HAMRICK/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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