842
FXUS02 KWBC 231930
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
330 PM EDT THU OCT 23 2025
VALID 12Z SUN OCT 26 2025 - 12Z THU OCT 30 2025
...HEAVY RAIN POSSIBLE ACROSS THE CENTRAL GULF COAST SUNDAY AND
MOVING NORTHEAST AS THE WEEK PROGRESSES...
..OVERVIEW
A SPLIT UPPER LEVEL FLOW PATTERN WILL BE IN PLACE ACROSS THE LOWER
48 INTO SUNDAY, WITH A SOUTHERN STREAM SHORTWAVE CROSSING THE
SOUTH-CENTRAL TO SOUTHEASTERN U.S. CAUSING A HEAVY RAIN AND
ISOLATED FLASH FLOODING THREAT. MEANWHILE, AN UPPER TROUGH OVER THE
WESTERN U.S. EARLY NEXT WEEK WILL HERALD A PATTERN CHANGE TO THE
REGION, WITH COLDER CONDITIONS AND WIDESPREAD SNOW FOR THE HIGHER
TERRAIN THROUGH MONDAY, AND PERIODS OF LIGHT TO MODERATE RAIN FOR
THE PACIFIC NORTHWEST COAST. THIS WESTERN U.S. TROUGH SHOULD PUSH
ENERGY SOUTHEASTWARD SOMEWHERE IN THE CENTRAL U.S. EARLY TO
MIDWEEK, BUT WITH AMPLE MODEL UNCERTAINTY. THIS FEATURE AND A
POSSIBLY DEVELOPING EAST COAST/WESTERN ATLANTIC LOW COULD PRODUCE
WIDESPREAD RAIN IN PORTIONS OF THE OHIO VALLEY, APPALACHIANS, AND
EAST COAST NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS IN REASONABLY GOOD AGREEMENT THROUGH THE EARLY
PART OF THE FORECAST PERIOD. THE SOUTHERN STREAM UPPER AND SURFACE
LOWS TRAVERSING THE SOUTH-CENTRAL U.S. SUNDAY COULD BE HANDLED BY A
MULTI-MODEL BLEND. THE SAME WAS TRUE FOR NORTHWESTERN U.S.
TROUGHING AND ANOTHER NORTHERN STREAM TROUGH IN THE EAST. HOWEVER,
AS NEXT WEEK PROGRESSES, MODEL GUIDANCE DIVERGES CONSIDERABLY WITH
THE TRACK OF A VORT MAX COMING OUT OF THE WESTERN TROUGH
POTENTIALLY DEVELOPING A CLOSED UPPER LOW. THE 00Z AND NEWER 12Z
CMC RUNS APPEAR TO BE OUTLIERS IN DIVING ENERGY FARTHER SOUTH
ACROSS THE SOUTH-CENTRAL PLAINS BY MONDAY AND TUESDAY COMPARED TO
OTHER GUIDANCE. WHILE THE CMC IS FARTHEST WEST AND THEREFORE NOT
PREFERRED, THERE IS SOME GUIDANCE THAT SUPPORTS THIS ENERGY MOVING
SOUTHEAST RATHER THAN BASICALLY STRAIGHT EAST LIKE EARLIER MODEL
CYCLES FAVORED, NAMELY THE 12Z GFS AND SOME AIFS RUNS. ANOTHER
COMPLICATING FACTOR IS THE TROUGHING IN THE EAST POTENTIALLY
RETROGRADING AND INTERACTING WITH THIS ENERGY OVER THE GREAT LAKES
OR SO. ALL THIS HAS IMPLICATIONS ON THE POTENTIAL DEVELOPMENT OF A
COASTAL LOW TOO. ECMWF AND EC ENSEMBLE MEMBERS HAVE BEEN HEAVILY
FAVORING A COASTAL LOW THAT COULD BECOME STRONG BY THE END OF THE
PERIOD, WHILE GFS AND GEFS DO NOT INDICATE A COASTAL LOW UNTIL
LATER THAT IS WEAKER. AI/ML MODELS ARE SPLIT ON IF AND WHEN ANY
NOTABLE COASTAL LOW DEVELOPS, SO THIS IS STILL AN AREA OF
SIGNIFICANT UNCERTAINTY IN THE FORECAST.
THE WPC FORECAST WILL OF COURSE FOLLOW THE NATIONAL HURRICANE
CENTER TRACK FOR MELISSA IN THE CARIBBEAN, WHICH BY THE MEDIUM
RANGE PERIOD WILL BE MUCH SLOWER THAN THE GFS RUNS THAT ACCELERATE
THE SYSTEM NORTHEASTWARD MUCH FASTER THAN CONSENSUS.
THE WPC FORECAST OUTSIDE THE TROPICS BEGINS WITH A BLEND OF THE
00Z/06Z GFS, 00Z ECMWF, AND LESSER PROPORTION OF THE 00Z UKMET.
INTO THE MID AND LATE PERIOD, QUICKLY INCREASED THE PROPORTION OF
ENSEMBLE MEANS TO A LITTLE OVER HALF DAY 6 AND MORE DAY 7 GIVEN THE
INCREASING SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAINFALL IS EXPECTED ACROSS PORTIONS OF THE CENTRAL GULF
COAST REGION GOING INTO SUNDAY AS THE SOUTHERN STREAM SHORTWAVE
TRACKS EAST ACROSS THE REGION, ALONG WITH A SURFACE LOW PRESSURE
SYSTEM. MODELS INDICATE 1 TO 3 INCHES OF RAIN COULD BE RELATIVELY
WIDESPREAD ACROSS THE MID-SOUTH AND SOUTHEAST ON SUNDAY. THE
HEAVIEST RAINFALL RATES AND RAIN TOTALS ARE POSSIBLE ACROSS THE
CENTRAL GULF COAST, BUT THE RELATIVELY FAST MOVEMENT OF MCSS THERE
AND THE HIGH FLASH FLOOD GUIDANCE WILL PRECLUDE ADDING A SLIGHT
RISK FOR NOW, AND WILL MAINTAIN A MARGINAL RISK ACROSS THESE AREAS
FOR THE DAY 4 ERO. AS THIS LOW PRESSURE SYSTEM TRACKS EAST AND
ANOTHER MAY DEVELOP OFFSHORE, RAIN CHANCES ARE FORECAST TO SPREAD
INTO THE APPALACHIANS AND CAROLINAS INTO THE SOUTHERN MID-ATLANTIC
ON MONDAY. EXPANDED THE MARGINAL RISK IN THE DAY 5 ERO TO INCLUDE
NOT JUST THE COASTAL RAIN BUT BACK INTO THE SOUTH-CENTRAL
APPALACHIANS THAT CAN BE SENSITIVE TO HEAVY RAIN CAUSING FLASH
FLOODING. AS THESE FEATURES INTERACT WITH ADDITIONAL ENERGY TO THE
WEST, MORE RAIN COULD OVERSPREAD THE OHIO VALLEY AND APPALACHIANS
TO MID-ATLANTIC BY MIDWEEK, BUT FORECAST DETAILS ARE LIKELY TO
CHANGE GIVEN THE MODEL SPREAD AT THIS POINT.
TROUGHING ACROSS THE NORTHWEST AND THE TAIL END OF AN ATMOSPHERIC
RIVER WILL LEAD TO PRECIPITATION THERE, INCLUDING HIGHER ELEVATION
SNOW THAT WILL LIKELY BE HEAVY IN THE CASCADES AND PERHAPS INTO THE
NORTHERN ROCKIES SUNDAY INTO MONDAY, WITH 1 TO 2 FEET OF SNOW
POSSIBLE. ENERGY FROM THE WESTERN TROUGH SHOULD PUSH A FRONT
THROUGH THE NORTH-CENTRAL U.S. FOR RAIN CHANCES IN THE DAKOTAS AND
UPPER MIDWEST ESPECIALLY ON MONDAY. THIS RAIN LOOKS TO HAVE LOW
RATES GIVEN LACK OF INSTABILITY, AND SINCE THIS DOES NOT TEND TO BE
AN AREA THAT IS SENSITIVE TO FLOODING, HAVE REMOVED THE MARGINAL
RISK THAT WAS IN THE PREVIOUS DAY 5 ERO. GUSTY WINDS ARE POSSIBLE
IN THE NORTH-CENTRAL ROCKIES TO PLAINS EARLY NEXT WEEK WITH THIS
SYSTEM AS WELL.
COOLER WEATHER WILL BE IN PLACE ACROSS THE WEST EARLY NEXT WEEK,
ESPECIALLY THE NORTHWEST THROUGH MONDAY WHERE HIGHS ARE FORECAST TO
BE 10 TO 15 DEGREES BELOW AVERAGE. AFTER THAT THE REGION IS
FORECAST TO WARM CLOSER TO NORMAL. MEANWHILE, MUCH OF THE PLAINS
WILL BE NEAR TO ABOVE AVERAGE EARLY NEXT WEEK BEFORE A COOLDOWN
MIDWEEK AS COLDER HIGH PRESSURE BUILDS IN BEHIND A COLD FRONT. MUCH
OF THE EAST COAST REGION SHOULD GENERALLY BE SLIGHTLY BELOW
AVERAGE THROUGH MOST OF THE FORECAST PERIOD.
TATE
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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