718
FXUS02 KWNH 290642
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 AM EDT WED OCT 29 2025
VALID 12Z SAT NOV 01 2025 - 12Z WED NOV 05 2025
..OVERVIEW
LATEST GUIDANCE CONTINUES TO ADVERTISE AN AMPLIFIED UPCOMING
MEDIUM RANGE PATTERN ALOFT, AT LEAST THROUGH THIS WEEKEND, WHICH
FEATURES MEAN TROUGHING OVER THE EASTERN U.S. AND A BUILDING RIDGE
OUT WEST. A SHORTWAVE DROPS SOUTHWARD FROM THE UPPER MIDWEST ON
SATURDAY TO BRING RENEWED AMPLIFIED TROUGHING OVER THE EAST WITH
LATEST GUIDANCE CONTINUING TO TREND TOWARD MORE STREAM SEPARATION
WITH A POSSIBLE CUTOFF CLOSED LOW OVER OR NEAR THE GULF COAST BY
EARLY NEXT WEEK, ALBEIT WITH STILL SIGNIFICANT UNCERTAINTY. THE
TAIL END OF AN ATMOSPHERIC RIVER WILL KEEP THE NORTHWEST STILL WET
INTO SATURDAY, BUT DRIER INTO EARLY NEXT WEEK WITH UPPER RIDGING.
ANOTHER DEEP TROUGH MAY APPROACH THE WEST COAST BY AROUND WEDNESDAY
OF NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MAIN FORECAST CONCERN CONTINUES TO BE WITH THE SHORTWAVE
DROPPING SOUTHWARD FROM THE UPPER MIDWEST INTO SATURDAY, WITH
POSSIBLE CUTOFF CLOSED LOW DEVELOPMENT OVER THE MISSISSIPPI VALLEY
TO GULF COAST BY SUNDAY OR MONDAY. LATEST TREND IN THE MODELS
CONTINUES TO BE FOR THIS SCENARIO, BUT THE CMC CONTINUES TO
ADVERTISE A GENERAL PROGRESSIVE AMPLIFIED TROUGH THROUGH THE
REGION. THE ENSEMBLE MEANS ARE MORE AMPLIFIED THAN THE CMC IS BUT
STILL SOMEWHAT PROGRESSIVE BUT THERE IS ALSO A TON OF SPREAD IN THE
INDIVIDUAL MEMBERS ADVERTISING BOTH SCENARIOS. THERE IS ALSO
UNCERTAINTY IN WHETHER ANY SORT OF CLOSED LOW WILL LINGER NEAR THE
GULF COAST (LIKE THE ECMWF) OR LIFT BACK OFF THE SOUTHEAST COAST
(LIKE THE GFS). THE WPC FORECAST TONIGHT STUCK CLOSE WITH
CONTINUITY AND THE GFS/ECMWF SHOWING MORE STREAM SEPARATION, BUT
DID TREND MORE WITH ENSEMBLE MEANS LATE IN THE PERIOD AMIDST
SIGNIFICANT UNCERTAINTY. OUT WEST, THERE IS QUESTION ON THE TIMING
OF THE NEXT TROUGH TOWARDS THE COAST LATE PERIOD AND AN ENSEMBLE
MEAN BLEND SEEMED TO SUFFICE AS A STARTING POINT.
..WEATHER/HAZARDS HIGHLIGHTS
A DEPARTING STRONG SURFACE LOW OUT OF THE NORTHEAST/CANADIAN
MARITIMES WILL INDUCE LAKE EFFECT RAINS BEHIND IT. THE SHORTWAVE
DROPPING THROUGH THE MIDWEST MAY BRING SOME UNCERTAIN LIGHT RAIN
SHOWERS WITH IT, BUT ADDITIONAL RAINFALL MAY DEVELOP ALONG THE GULF
COAST WITH WEAK SURFACE LOW DEVELOPMENT ALONG A TRAILING FRONTAL
BOUNDARY IN THE GULF. RAIN MAY EXPAND IN COVERAGE ACROSS THE
SOUTHEAST AND EAST COAST EARLY NEXT WEEK, BUT WITH MUCH MORE
UNCERTAINTY AND HIGHLY DEPENDENT ON THE PATTERN EVOLUTION OVER THIS
REGION NEXT WEEK.
LOCALLY MODERATE TO HEAVY PRECIPITATION MAY LINGER INTO SATURDAY
ON THE BACK END OF A MODERATELY STRONG ATMOSPHERIC RIVER INTO THE
NORTHWEST LATE THIS WEEK. BUT BY SATURDAY, INSTABILITY SHOULD BE
LESS AND THE BETTER MOISTURE ANOMALIES WILL BE QUICKLY SHIFTING
EASTWARD SO NO MARGINAL RISK IS PLANNED AT THIS TIME ON THE ERO
SINCE FRIDAY SHOULD BE THE BIGGER DAY. MOST PRECIPITATION IS
FORECAST TO STAY RAIN OTHER THAN SNOW IN THE HIGHEST PEAKS OF THE
OLYMPICS AND THE CASCADES. THE REGION SHOULD TREND DRIER SUNDAY
WITH POSSIBLY ANOTHER INCREASE IN PRECIPITATION INTO EARLY NEXT
WEEK AGAIN. ELSEWHERE, THE SOUTHWEST TO THE PLAINS SHOULD STAY
MOSTLY DRY THROUGH THE PERIOD UNDER THE WARMING RIDGE ALOFT.
MUCH OF THE WEST CAN EXPECT WARMER THAN AVERAGE TEMPERATURES
UNDERNEATH UPPER RIDGING THROUGH THE PERIOD, EXPANDING INTO THE
CENTRAL U.S. SUNDAY AND BEYOND. MEANWHILE, THE EAST WILL BE MAINLY
NEAR OR JUST BELOW NORMAL TEMPERATURES UNDERNEATH MEAN UPPER
TROUGHING.
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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