065
FXUS02 KWBC 070656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT SAT SEP 7 2024
VALID 12Z TUE SEP 10 2024 - 12Z SAT SEP 14 2024
...MULTI-DAY WESTERN GULF COAST STATES HEAVY RAINFALL/FLOODING
THREAT THROUGH EARLY-MID NEXT WEEK ALSO BEING MONITORED BY NHC...
..OVERVIEW
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 THE
WEEK AS AN UPPER TROUGH BUILDS IN ACROSS THE WEST COAST AND THEN
THE INTERMOUNTAIN WEST. HEAVY RAIN AND THUNDERSTORMS WILL CONTINUE
TO MAKE WEATHER HEADLINES FOR THE WESTERN GULF COAST AS ANOTHER
RESURGENCE OF GULF MOISTURE (CURRENTLY MONITORED BY NHC) MOVES
INLAND ACROSS TEXAS BY TUESDAY NIGHT INTO WEDNESDAY, BUT NOT MUCH
IN TERMS OF HEAVY RAINFALL ELSEWHERE ACROSS THE NATION WITH MAINLY
LIGHTER RAINFALL FOR THE NORTHWESTERN U.S. AND THE ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE FEATURES GOOD OVERALL SYNOPTIC SCALE
AGREEMENT ACROSS THE NATION ON TUESDAY, WITH THE GREATEST MODEL
SPREAD GENERALLY NORTH ACROSS SOUTHERN CANADA. THE GUIDANCE HAS
REMAINED CONSISTENT WITH THE AMPLIFYING TROUGH OVER THE
NORTHWESTERN U.S., WITH THE GFS A LITTLE QUICKER TO LIFT THE TROUGH
OUT ACROSS THE DAKOTAS ON FRIDAY. WITH THE DISTURBANCE APPROACHING
TEXAS, THE ENSEMBLE MEMBERS STILL VARY QUITE A BIT WITH LOW
PLACEMENTS AND INTENSITY, SO THIS IS SOMETHING TO CLOSELY MONITOR
IN THE DAYS AHEAD.
FOR THE WPC OVERNIGHT FORECAST, A BLEND OF THE DETERMINISTIC
GFS/CMC/UKMET/ECMWF WAS USED AS A BASELINE THROUGH WEDNESDAY, WITH
A LITTLE MORE WEIGHTING TO THE ECMWF GUIDANCE. ENSEMBLE MEANS WERE
ADDED GRADUALLY TO MAKE UP ABOUT 50% OF THE BLEND BY SATURDAY,
WHICH HELPED TO SMOOTH OUT INCREASING MESOSCALE DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
INCREASING TROPICAL MOISTURE OVER THE SOUTHWESTERN GULF OF
MEXICO/BAY OF CAMPECHE OVER THE NEXT FEW DAYS IS EXPECTED TO BRING
AN INCREASING THREAT FOR HEAVY RAIN AND STRONG STORMS TO THE
COASTAL AREAS OF THE TEXAS GULF COAST BY EARLY TO MIDDLE 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 THE GREATER CORPUS CHRISTI AREA TO
NEAR LAKE CHARLES, WHERE A FEW 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
ACROSS THE CENTRAL TEXAS GULF COAST. A SLIGHT RISK IS PLANNED FROM
THE GREATER HOUSTON METRO AREA TO NEAR BATON ROUGE, AND A MARGINAL
RISK EXTENDING EASTWARD TO THE GEORGIA COAST.
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
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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