716
FXUS02 KWBC 300651
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 AM EDT THU OCT 30 2025
VALID 12Z SUN NOV 02 2025 - 12Z THU NOV 06 2025
..OVERVIEW
SHORTWAVE ENERGY DIVING SOUTHWARD THROUGH THE MIDWEST WILL CLOSE
OFF AN UPPER LOW WHICH LOOKS TO TRAVERSE THE GULF COAST BEFORE
WEAKENING AND LIFTING OFF THE SOUTHEAST COAST AROUND NEXT TUESDAY.
MEANWHILE, NORTHERN STREAM ENERGY WILL SWING THROUGH THE GREAT
LAKES AT THE SAME TIME. OUT WEST, AN INITIAL WEAKER ATMOSPHERIC
RIVER SHOULD KEEP THE REGION SHOWERY, BUT A STRONGER AR LOOKS TO
MOVE INTO THE REGION BY THE MIDDLE OF NEXT WEEK BRINGING A THREAT
FOR MODERATE TO HEAVY RAINFALL AND MOUNTAIN SNOWS FOR PARTS OF
WASHINGTON, OREGON, NORTHERN CALIFORNIA, AND THE SIERRA NEVADA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MAIN FORECAST CONCERN CONTINUES TO BE WITH THE SHORTWAVE
TROUGH DROPPING SOUTHWARD, WITH POSSIBLE CUTOFF CLOSED LOW
DEVELOPMENT OVER THE MISSISSIPPI VALLEY TO GULF COAST ON SUNDAY
INTO MONDAY. THE GUIDANCE IS NOW IN AGREEMENT WITH THE PRESENCE OF
THIS SYSTEM, BUT DO SHOW CONSIDERABLE TIMING CONCERNS, EVEN AS
EARLY AS DAY 4 WITH HOW QUICKLY IT EXITS THE GULF COAST/SOUTHEAST
REGION. THE CMC IS THE WEAKEST WITH THIS LOW AND FASTER TO SWING
THROUGH THE SOUTHEAST, WITH THE GFS THE DEEPEST AND SLOWEST. THE
ECMWF IS A NICE MIDDLE GROUND, BUT STILL A BIT FAST COMPARED TO WPC
CONTINUITY AND THE ENSEMBLE MEANS. THE NEW 00Z GUIDANCE TONIGHT
(WHICH CAME IN AFTER THE INITIAL FORECAST BLEND) SHOWS A BIT FASTER
GFS SOLUTION, AND SLOWER CMC. THE ECMWF ALSO TRENDED SLOWER, BUT
NOW SHOWS ENERGY LINGERING OVER THE GULF FOR AN EXTRA DAY. SO THERE
REMAINS CONSIDERABLE UNCERTAINTY IN THE DETAILS OF THIS SYSTEM
WHICH OF COURSE HAS HUGE IMPLICATIONS ON RAINFALL DISTRIBUTION AND
AMOUNTS ACROSS THE SOUTHEAST. THE WPC FORECAST TONIGHT WAS BASED ON
A BLEND OF THE SLOWER 12Z GFS WITH THE ECMWF AND WPC CONTINUITY
WHICH RESULTED IN A POSITION IN BETWEEN THE ECMWF AND GFS.
OUT WEST, A WEAK SHORTWAVE WILL SWING THROUGH EARLY IN THE PERIOD,
WITH A MUCH STRONGER AND DEEPER TROUGH INTO THE WEST COAST AROUND
WEDNESDAY TO THURSDAY OF NEXT WEEK. THERE IS SOME TIMING
UNCERTAINTIES STILL WITH THIS SYSTEM WITH THE CMC FASTEST TO BRING
THE SYSTEM INLAND. THE WPC FORECAST WAS BASED ON A BLEND OF THE
MORE AGREEABLE GFS AND ECMWF WITH THE ENSEMBLE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
EXPECT RAINFALL TO DEVELOP ALONG THE GULF COAST WITH WEAK SURFACE
LOW DEVELOPMENT ALONG A TRAILING FRONTAL BOUNDARY IN THE GULF BY
SUNDAY. RAIN COVERAGE MAY EXPAND FOR THE SOUTHEAST AND EAST COAST
EARLY NEXT WEEK, BUT WITH MUCH UNCERTAINTY AND HIGHLY DEPENDENT ON
THE PATTERN EVOLUTION INTO THIS REGION. AT THIS POINT, MODELS ARE
NOT SHOWING MUCH MORE THAN MODERATE SHOWERS, BUT THIS COULD CHANGE
DEPENDING ON THE STRENGTH OF THE UPPER LOW. THE NORTHERN STREAM
ENERGY THROUGH THE GREAT LAKES MAY BRING LIGHT RAIN TO THIS REGION
EARLY IN THE PERIOD AS WELL.
THE NORTHWEST SHOULD TREND DRIER SUNDAY BEHIND AN INITIAL
ATMOSPHERIC RIVER INTO THE REGION EARLY IN THE PERIOD. ANOTHER
INCREASE IN PRECIPITATION EARLY WEEK IS EXPECTED, BUT A MORE
FAVORABLE AR PATTERN AND INCREASED MOISTURE LOOKS TO MOVE IN NEXT
WEDNESDAY WITH LOCALLY MODERATE TO HEAVY RAINFALL POSSIBLE AND SNOW
IN THE HIGHEST ELEVATIONS. ELSEWHERE, THE SOUTHWEST TO THE PLAINS
SHOULD STAY DRY THROUGH THE PERIOD UNDER AN UPPER RIDGE.
MUCH OF THE SOUTHWEST/INTERIOR WEST TO CENTRAL U.S. AND MIDWEST
WILL BE WARMER THAN AVERAGE WITH STRONG UPPER LEVEL RIDGING THROUGH
THE PERIOD. DAYTIME HIGHS COULD AVERAGE 10 TO 20 DEGREES ABOVE
NORMAL EACH DAY. MEANWHILE, BELOW NORMAL TEMPERATURES NEAR THE GULF
COAST/SOUTHEAST ASSOCIATED WITH THE UPPER CUTOFF LOW SHOULD
MODERATE AFTER MONDAY.
SANTORELLI
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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