758
FXUS02 KWBC 030604
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
204 AM EDT SAT OCT 3 2026
VALID 12Z TUE OCT 06 2026 - 12Z SAT OCT 10 2026
...PERSISTENT HEAVY RAINFALL THREAT CONTINUES ACROSS THE GULF COAST
INTO SOUTHEAST/FLORIDA INTO TUESDAY...
..LONG DURATION LATE-SEASON HEAT WAVE EXPECTED FOR CALIFORNIA
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL GUIDANCE CONTINUES TO SHOW A FAIRLY WELL-DEFINED
LARGE-SCALE PATTERN WITH THE RIDGING ACROSS WESTERN U.S. AND BROAD
TROUGHING EXTENDING FROM THE NORTHERN STREAM INTO EASTERN U.S.. BY
LATE- WEEK, THE PRIMARY UNCERTAINTY WILL BE THE EVOLUTION OF THE
WESTERN RIDGE AND THE INTERACTION WITH THE SHORTWAVE MOVING INTO
THE PACIFIC NORTHWEST, WHICH WILL IMPACT TIMING AND AMPLITUDE OF
PRECIPITATION AND COOLER TEMPERATURES. MOST MODELS SHOW A GOOD
AGREEMENT OF EASTWARD MOVEMENT OF THE RIDGE, BUT DIFFERS ON HOW
QUICKLY THE RIDGE SHIFTS AND THE STRENGTH OF THE PACIFIC TROUGH.
ACROSS THE SOUTHEAST, MODELS SHOW DIFFERENCES WITHIN THE TIMING AND
POSITION OF THE FRONTAL BOUNDARY OVER THE GULF COAST INTO FLORIDA,
WHICH WILL IMPACT THE LOCATION FOR THE HIGHEST RAINFALL AXIS.
THE LATEST ENSEMBLE GUIDANCE GENERALLY MAINTAINS THE LARGE-SCALE
PATTERN, WHILE FAVORING A SLOW EASTWARD MOVEMENT OF THE WESTERN
RIDGE. THEREFORE, THE FORECAST WAS BASED ON A MULTI-MODEL BLEND
THROUGH MIDWEEK, WITH A HEAVIER WEIGHT OF THE ENSEMBLE MEANS
TOWARDS LATE WEEK TO HELP MITIGATE THE DIFFERENCES.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
A BROAD UPPER TROUGH OVER EASTERN U.S. WILL PERSIST THROUGH THE
WEEK, REINFORCING UNSETTLED WEATHER ACROSS THE SOUTHEAST. THE
PRIMARY FOCUS FOR RAINFALL WILL REMAIN ALONG THE GULF COAST AND
INTO FLORIDA, WHERE A SLOW-MOVING FRONTAL BOUNDARY WILL INTERACT
WITH DEEP TROPICAL MOISTURE. THIS SETUP IS FAVORABLE FOR A
PROLONGED PERIOD OF SHOWERS AND THUNDERSTORMS ALONG THE BOUNDARY.
REPEATED ROUNDS OF CONVECTION MAY LEAD TO LOCALIZED FLASH FLOODING
RISK ACROSS PORTIONS OF NORTHERN FLORIDA THROUGH WEDNESDAY, WHICH
IS REFLECTED IN THE WPC EXCESSIVE RAINFALL OUTLOOK FOR
DAY4/WEDNESDAY. THE BOUNDARY IS EXPECTED TO REMAIN STALLED THROUGH
LATE WEEK, BRINGING DAILY SHOWERS AND THUNDERSTORMS THAT MAY
CONTINUE FLASH FLOODING RISK INTO THURSDAY.
FARTHER NORTH, A SERIES OF NORTHERN -STREAM SHORTWAVES WILL
PROGRESS EASTWARD FROM THE NORTHERN ROCKIES/PLAINS TOWARDS THE
MIDWEST AND NORTHEAST. THESE DISTURBANCES WILL REINFORCE THE
BROADER EASTERN TROUGH, WHICH WILL SUPPORT PERIODIC LIGHT SHOWERS
ALONG ASSOCIATED FRONTAL BOUNDARIES ACROSS THE UPPER MIDWEST/GREAT
LAKES INTO THE NORTHEAST. BEHIND THE FRONT, COOLER AIR WILL BRING
BELOW NORMAL TEMPERATURES FROM THE NORTHEAST INTO PORTIONS OF THE
MID- ATLANTIC/SOUTHEAST THROUGH WEDNESDAY.
ACROSS THE WEST, UPPER RIDGING WILL CONTINUE TO SUPPORT ABOVE
NORMAL TEMPERATURES, ESPECIALLY ACROSS CALIFORNIA AND DESERT
SOUTHWEST. DAYTIME HIGHS ARE EXPECTED TO REACH UPPER 90S TO LOW
100S, WITH MUCH OF SOUTHERN CALIFORNIA UNDER A MODERATE TO EXTREME
HEATRISK.THE RIDGE SHOULD GRADUALLY WEAKEN AND SHIFT EASTWARD BY
LATE WEEK, BUT THE PERSIST HEAT WILL BRING CONCERNS FOR HEAT-
RELATED ILLNESS, ESPECIALLY FOR THOSE WITHOUT ADEQUATE COOLING AND
HYDRATION. SEE WPC'S KEY MESSAGES FOR THE CALIFORNIA OCTOBER HEAT
WAVE FOR ADDITIONAL INFORMATION. BY LATE WEEK, SCATTERED SHOWERS
MAY DEVELOP FOR THE PACIFIC NORTHWEST AS THE NEXT SHORTWAVE
APPROACHES.
OUDIT
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
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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