658
FXUS02 KWNH 040547
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 AM EDT SUN OCT 4 2026
VALID 12Z WED OCT 07 2026 - 12Z SUN OCT 11 2026
...PERSISTENT HEAVY RAINFALL THREAT CONTINUES ACROSS THE GULF COAST
INTO SOUTHEAST/FLORIDA INTO THURSDAY...
..LONG DURATION LATE-SEASON HEAT WAVE EXPECTED FOR CALIFORNIA
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODELS GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT
REGARDING THE PERSISTENCE OF THE EASTERN U.S. TROUGHING THROUGH THE
PERIOD, BUT SPREAD INCREASES IN REGARD TO THE EVOLUTION OF THE
EAST PACIFIC TROUGH. SOME GUIDANCE SUPPORTS A MORE AMPLIFIED
WESTERN TROUGH AND QUICKER EROSION OF THE RIDGE, WHILE OTHER
SOLUTIONS MAINTAIN A STRONGER RIDGE, DELAYING COOLER CONDITIONS.
THIS WILL ALSO IMPACT THE TIMING AND INTENSITY OF PRECIPITATION
DEVELOPING ACROSS THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES.
ADDITIONALLY, DETERMINISTIC MODELS CONTINUE TO SHOW DIFFERENCES
WITH THE PLACEMENT OF THE FRONTAL BOUNDARY OVER THE GULF COAST INTO
THE SOUTHEAST AND FLORIDA, WHICH IMPACTS THE PLACEMENT OF THE
HEAVIEST RAINFALL AXIS.
A GENERAL MULTI-MODEL BLEND IS PREFERRED FOR THE FORECAST, WITH
INCREASING WEIGHT TOWARDS THE ENSEMBLE MEANS AND AI GUIDANCE
TOWARDS DAYS 5 THROUGH 7. THIS APPROACH SHOULD HELP MITIGATE THE
TENDENCY FOR INDIVIDUAL DETERMINISTIC RUNS TO BECOME OVERLY
AMPLIFIED WITH SMALLER-SCALE SHORTWAVE FEATURES, WHILE RETAINING
THE SIGNAL FOR THE WESTERN TROUGH.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
THE LARGE-SCALE PATTERN THROUGH THE PERIOD WILL FEATURE A
PRONOUNCED MEAN TROUGH OVER EASTERN U.S., RIDGING OVER WESTERN
U.S., AND TROUGHING OVER EASTERN PACIFIC. AT THE SURFACE, A SLOW-
MOVING FRONTAL BOUNDARY SHOULD REMAIN DRAPED FROM THE GULF COAST
INTO THE SOUTHEAST AND FLORIDA THROUGH THE WEEKEND. DEEP TROPICAL
MOISTURE POOLED ALONG THE BOUNDARY WILL SUPPORT REPEATED ROUNDS OF
SHOWERS AND THUNDERSTORMS, PARTICULARLY ACROSS FLORIDA AND ADJACENT
PORTIONS OF THE SOUTHEAST. TRAINING CONVECTION AND HIGH RAINFALL
RATES COULD PRODUCE LOCALLY EXCESSIVE RAINFALL, PARTICULARLY WHERE
STORMS REPEATEDLY OCCUR. THEREFORE, WPC EXCESSIVE RAINFALL
OUTLOOK CONTINUES TO HIGHLIGHT A MARGINAL RISK FOR PORTIONS OF
FLORIDA ON DAY 4/THURSDAY. THE GREATEST HEAVY-RAIN POTENTIAL
SHOULD
GRADUALLY SHIFT WITH THE POSITION OF THE FRONT, BUT FLORIDA REMAINS
THE FAVORED AREA FOR PROLONGED CONVECTION THROUGH THURSDAY. BY THE
WEEKEND, THE AXIS OF HEAVY RAINFALL SHIFTS EASTWARD ALONG THE GULF
COAST.
ACROSS THE MIDWEST INTO THE NORTHEAST, THE PERSISTENT UPPER TROUGH
SHOULD MAINTAIN GENERALLY COOLER CONDITIONS. PERIODIC SHORTWAVES
ROTATING THROUGH THE TROUGH MAY PRODUCES AREAS OF LIGHT SHOWERS,
PARTICULARLY NEAR FRONTAL BOUNDARIES. FARTHER WEST, UPPER RIDGING
SHOULD CONTINUE TO SUPPORT ABOVE AVERAGE TEMPERATURES. HIGHS IN
THE UPPER 90S TO LOWER 100S WILL REMAIN POSSIBLE ACROSS PORTIONS OF
THE SOUTHWEST AND SOUTHERN CALIFORNIA. WARM OVERNIGHT TEMPERATURES
WILL ALSO LIMIT RELIEF FROM THE HEAT, LEADING TO HEAT-RELATED
ILLNESS CONCERNS ESPECIALLY FOR THOSE WITHOUT ADEQUATE COOLING AND
HYDRATION. SEE WPC'S KEY MESSAGES FOR THE CALIFORNIA OCTOBER HEAT
WAVE FOR ADDITIONAL INFORMATION. THE RIDGE SHOULD GRADUALLY WEAKEN
AND SHIFT AS THE EASTERN PACIFIC TROUGH BECOMES MORE AMPLIFIED BY
FRIDAY. ADDITIONALLY, AS THE TROUGH CONTINUES TO MOVE INLAND,
PRECIPITATION CHANCES INCREASES INTO THE WEEKEND OVER PACIFIC
NORTHWEST INTO THE NORTHERN ROCKIES.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page