448
FXUS02 KWBC 050648
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 AM EDT MON OCT 5 2026
VALID 12Z THU OCT 08 2026 - 12Z MON OCT 12 2026
...EXCESSIVE RAINFALL/FLASH FLOOD THREAT CONTINUES FOR CENTRAL
GULF COAST AND SOUTHEAST THROUGH FRIDAY...
..HEAT WAVE IN CALIFORNIA BEGINS TO WEAKEN ON THURSDAY
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUES TO SUPPORT A BROAD UPPER TROUGH ACROSS EASTERN
CANADA INTO EASTERN U.S. WHILE GREATEST SPREAD DEVELOPS OVER THE
WESTERN U.S. AS THE UPSTREAM EASTERN PACIFIC TROUGH INTERACTS WITH
THE WESTERN RIDGE. THE LATEST GUIDANCE CONTINUES TO DIFFER ON THE
TIMING AND AMPLITUDE OF THE TROUGH, ESPECIALLY TOWARDS THE WEEKEND.
THE FORECAST IS BASED PRIMARILY ON A MULTI-MODEL/ENSEMBLE
CONSENSUS, WITH INCREASING RELIANCE ON THE ENSEMBLE MEANS WITH
TIME TO MITIGATE DETERMINISTIC RUN-TO-RUN VARIABILITY. THIS
APPROACH SUPPORTED THE LARGE-SCALE AGREEMENT WHILE SMOOTHING SOME
OF THE DIFFERENCES WITHIN INDIVIDUAL SHORTWAVES, FRONTAL TIMING,
AND CONVECTIVE EVOLUTION..
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
THE BROAD MEAN TROUGH OVER EASTERN U.S. WILL REMAIN WELL
ESTABLISHED THROUGH THE PERIOD, WHILE A REINFORCING SHORTWAVE
ROTATING THROUGH THE BASE WILL SUPPORT ANOTHER SURFACE FRONTAL
PROGRESSION ACROSS THE MIDWEST, GREAT LAKES, AND NORTHEAST BRINGING
COOLER CONDITIONS BEHIND THE FRONT. FARTHER SOUTH, THE GULF
COAST/SOUTHEAST WILL REMAIN COMPARATIVELY WARM BENEATH PERSISTENT
SOUTHERLY FLOW AHEAD OF THE SLOW-MOVING FRONTAL BOUNDARY. DEEP
TROPICAL MOISTURE WILL CONTINUE TO INTERACT WITH THE BOUNDARY,
LEADING TO SHOWERS AND THUNDERSTORM DEVELOPMENT ACROSS THE
SOUTHEAST, GULF COAST, AND FLORIDA THROUGH SATURDAY. THE
COMBINATION OF INCREASING LOW- LEVEL MOISTURE, WEAK FRONTAL
PROGRESSION, AND LOCALLY FAVORABLE LOW- TO MID-LEVEL FLOW MAY LEAD
TO EXCESSIVE RAINFALL AND LOCALIZED FLOODING ALONG THE GULF COAST.
WITH THE POTENTIAL FOR REPEATED CONVECTION AND HIGH RAINFALL RATES,
WPC HAS PLACED A MARGINAL RISK ACROSS THE GULF COAST INTO EASTERN
TEXAS COAST AND PORTIONS OF WESTERN TEXAS IN THE EXCESSIVE RAINFALL
OUTLOOK FOR DAY4/THURSDAY. THE MARGINAL RISK CONTINUES FOR THE
GULF COAST INTO AND WESTERN TEXAS FOR DAY5/FRIDAY. BY SATURDAY,
THE HEAVIEST RAINFALL AXIS STARTS TO EXPAND INLAND ACROSS THE
SOUTHEAST. ON SUNDAY, A PORTION OF THE FRONTAL BOUNDARY WILL
GRADUALLY LIFT NORTHWARD ALONG THE EAST COAST, SPREADING SHOWERS
AND THUNDERSTORMS FROM THE SOUTHEAST INTO THE NORTHEAST.
ACROSS THE WEST, UPPER RIDGING WILL CONTINUE TO SUPPORT DRY AND
ANOMALOUSLY WARM TEMPERATURES THROUGH THURSDAY. THE STRONGEST HEAT
WILL PERSIST FOR PORTIONS OF CALIFORNIA AND SOUTHWEST, WHERE HIGHS
ARE EXPECTED TO REACH 90S TO LOW 100S. WARM OVERNIGHT TEMPERATURES
WILL ALSO LIMIT RELIEF FROM THE HEAT, LEADING TO HEAT-RELATED
ILLNESS CONCERNS ESPECIALLY FOR THOSE WITHOUT ADEQUATE COOLING AND
HYDRATION. THE RIDGE WILL GRADUALLY WEAKEN AS THE EASTERN PACIFIC
APPROACHES THE COAST BY FRIDAY. THIS WILL BRING PRECIPITATION
CHANCES ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES,
ESPECIALLY ON SATURDAY INTO SUNDAY AS THE TROUGH BECOMES MORE
AMPLIFIED. SHOWERS WILL CONTINUE TO EXPAND EASTWARD FROM THE
PACIFIC NORTHWEST/NORTHERN ROCKIES INTO PORTIONS OF THE MIDWEST BY
SUNDAY, WITH LOCALLY MODERATE TO HEAVY RAINFALL POSSIBLE ALONG
FAVORED TERRAIN AND FRONTAL ZONES. ADDITIONALLY, AS THE WESTERN
RIDGE WEAKENS, THE TROUGH WILL BRING COOLER TEMPERATURES THAT WILL
SPREAD ACROSS THE PACIFIC NORTHWEST INTO NORTHERN PLAINS THROUGH
THE WEEKEND.
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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