664
FXUS02 KWBC 250655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT SAT OCT 25 2025
VALID 12Z TUE OCT 28 2025 - 12Z SAT NOV 01 2025
..HEAVY RAIN POSSIBLE FOR THE EASTERN U.S. NEXT WEEK
..OVERVIEW
MODELS CONTINUE TO ADVERTISE AN AMPLIFIED AND ACTIVE UPCOMING
MEDIUM RANGE PATTERN. DEEP TROUGHING OVER THE CENTRAL U.S. TO START
THE PERIOD ON TUESDAY LOOKS TO CLOSE OFF AN UPPER LOW AS IT DROPS
SOUTH/SOUTHEASTWARD INTO THE MID-SOUTH. MEANWHILE, A RETROGRADING
UPPER LOW OVER THE NORTHEAST MAY INTERACT WITH THE SOUTHERN LOW
RESULTING IN POSSIBLY A LARGE CLOSED UPPER LOW (OR AT THE VERY
LEAST AMPLIFIED TROUGHING) INTO THE EAST NEXT WEEK AND POSSIBLE
COASTAL CYCLOGENESIS AND A HEAVY RAINFALL THREAT. UPPER RIDGING
WILL BUILD OVER THE INTERIOR WEST THROUGH THE PERIOD WITH WEAK
SHORTWAVES INTO THE PACIFIC NORTHWEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE SHOWS GOOD AGREEMENT THE FIRST DAY OR TWO OF
THE PERIOD, BUT QUICKLY DIVERGE WITH THE PATTERN SPECIFICS IN THE
EAST LATER NEXT WEEK. THERE IS GENERAL AGREEMENT ON SOME FORM OF
AMPLIFIED TROUGHING OR A CLOSED LOW OVER THE EAST BUT THE EVOLUTION
OF THAT LOW AND INTERACTIONS WITH THE RETROGRADING LOW OVER THE
NORTHEAST ARE HIGHLY VARIABLE. COMPARED TO A DAY AGO, GUIDANCE HAS
TRENDED SOUTH WITH AN UPPER LOW THAT FORMS OUT OF THE WEST-CENTRAL
U.S. TROUGH AROUND WEDNESDAY. THE GFS AND CMC ARE THE FARTHEST
SOUTH WITH IT NEAR THE GULF COAST LATER NEXT WEEK, AND THE ECMWF
(AND ECENS) ARE STILL ON THE NORTH SIDE WITH MUCH MORE INTERACTION
WITH ENERGY FROM THE NORTHEAST LOW. THIS OF COURSE, HAS MAJOR
IMPACT ON THE QPF AMOUNTS AND DISTRIBUTION ACROSS THE EAST NEXT
WEEK, AND THE WPC FORECAST MORE OR LESS STUCK CLOSE TO THE NBM FOR
THE SENSIBLE WEATHER GRIDS AMIDST SO MUCH UNCERTAINTY. COMPARED TO
WPC CONTINUITY, QPF IS FURTHER SOUTH/SLOWER TO EXIT THE EAST THIS
CYCLE. NEW 00Z GUIDANCE GENERALLY HOLDS WITH THEIR PREVIOUS RUNS
BUT BOTH THE GFS AND CMC ARE SLIGHTLY NORTH OF THEIR PREVIOUS
POSITIONS OF THE UPPER LOW OVER THE SOUTH. THE WPC FORECAST TONIGHT
WAS ABLE TO USE A MAJORITY DETERMINISTIC GUIDANCE THE FIRST HALF
OR SO OF THE PERIOD BUT QUICKLY TRANSITIONED TO HEAVILY WEIGHTED
WITH THE ENSEMBLE MEANS DAYS 5-7.
MEANWHILE, TROPICAL STORM MELISSA IN THE CARIBBEAN IS FORECAST TO
BE A SLOW MOVING MAJOR HURRICANE BY THE START OF THE MEDIUM RANGE
PERIOD NEAR OR OVER JAMAICA. ITS TRACK IS ALSO HIGHLY INFLUENCED BY
THE DEVELOPING TROUGH/LOW OVER THE EAST NEXT WEEK. THE TREND
CONTINUES TO BE FOR A TRACK WELL OFF THE EAST COAST, BUT MELISSA
MAY GET PICKED UP BY THE TROUGH/LOW AS IT EXITS THE NORTHEAST LATE
NEXT WEEK AND PULLED BACK IN TOWARDS THE CANADIAN MARITIMES. THE
CMC WAS MOST AGGRESSIVE WITH THIS SOLUTION WITH THE GFS CONTINUING
TO BE MUCH FASTER THAN CONSENSUS. MELISSA CONTINUES TO BE WORTH
MONITORING FOR ANY POTENTIAL CHANGES TO THE FORECAST. THE WPC
FORECAST WILL FOLLOW THE OFFICIAL FORECAST TRACK FROM THE NATIONAL
HURRICANE CENTER.
..WEATHER/HAZARDS HIGHLIGHTS
DEVELOPING LOW PRESSURE OVER THE MID-SOUTH BY TUESDAY WILL
CONTINUE TO SPREAD RAINFALL AHEAD OF IT THROUGH THE CAROLINAS AND
INTO THE MID-ATLANTIC TUESDAY INTO WEDNESDAY. FOR TUESDAY, QPF
AMOUNTS DO NOT SEEM HEAVY ENOUGH TO WARRANT A MARGINAL RISK ON THE
ERO EITHER IN THE EAST OR FARTHER WEST INTO THE OHIO VALLEY/MIDWEST
REGION. ON DAY 5/WEDNESDAY, AS THE UPPER LOW DEEPENS, IT MAY PULL
MORE TROPICAL ATLANTIC MOISTURE INTO THE CAROLINAS/MID-ATLANTIC
REGION AND BACK INTO THE SOUTHERN APPALACHIANS, BUT WITH A LOT OF
UNCERTAINTY ON THE AMOUNTS. GIVEN HOW SENSITIVE THE APPALACHIANS
ARE, OPTED FOR A MARGINAL RISK OVER THAT REGION FOR THE DAY 5 ERO.
AREAS CLOSER TO THE COAST WILL NEED TO CONTINUE TO BE MONITORED.
WITH POTENTIAL COASTAL LOW DEVELOPMENT NEXT WEEK, RAINFALL WILL
MOVE NORTHWARD WITH TIME, WITH HEAVY RAINFALL POSSIBLE, BUT STILL A
TON OF VARIABILITY ON THE AMOUNTS AND TIMING.
THE PACIFIC NORTHWEST SHOULD SEE ROUNDS OF RAIN AND MOUNTAIN SNOW
CHANCES THROUGH NEXT WEEK AS SHORTWAVES AND FRONTS MOVE THROUGH.
WEDNESDAY AND THURSDAY MAY HAVE A RELATIVE BREAK BEFORE A RENEWAL
OF PERHAPS HEAVY AMOUNTS LATE WEEK.
TEMPERATURES ACROSS THE WEST WILL TREND WARMER WITH TIME NEXT
WEEK, AS UPPER RIDGING BUILDS. TEMPERATURES ACROSS ESPECIALLY THE
CENTRAL AND NORTHERN HIGH PLAINS COULD BE 10 TO 20 DEGREES ABOVE
NORMAL BY NEXT SATURDAY. MEANWHILE, ACROSS THE SOUTH AND INTO THE
MID- ATLANTIC MAY BE WELL BELOW NORMAL UNDERNEATH A DEVELOPING
UPPER LOW, BUT MODERATE WITH TIME AS THE LOW LIFTS THROUGH THE
EAST.
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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