512
FXUS02 KWBC 271956
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 PM EDT MON OCT 27 2025
VALID 12Z THU OCT 30 2025 - 12Z MON NOV 03 2025
...HEAVY RAIN LIKELY FOR THE MID-ATLANTIC AND NORTHEAST THURSDAY
INTO FRIDAY...
..OVERVIEW
MODELS CONTINUE TO ADVERTISE AN AMPLIFIED AND ACTIVE UPCOMING
MEDIUM RANGE PATTERN WHICH FEATURES A COUPLE OF ROUNDS OF DEEP
TROUGHING WITH EMBEDDED UPPER LOWS OVER THE EASTERN U.S. AND A
BUILDING RIDGE OUT WEST. THE FIRST EASTERN UPPER LOW WILL BE OVER
THE MID-SOUTH BY THE START OF THE PERIOD ON THURSDAY, AND WILL LIFT
NORTHWARD ACROSS THE INTERIOR EAST AS ITS EASTERLY MOVEMENT GETS
BLOCKED BY A STRONG RIDGE OVER THE ATLANTIC. THIS BRINGS A RISK FOR
HEAVY RAINFALL TO PARTS OF THE MID-ATLANTIC AND NORTHEAST THURSDAY
INTO EARLY FRIDAY. ANOTHER SHORTWAVE ON THE BACKSIDE OF THE UPPER
LOW WILL DROP SOUTHWARD NEXT WEEKEND RENEWING AMPLIFIED TROUGHING
OVER THE EAST ONCE AGAIN EARLY NEXT WEEK. THE NORTHWEST WILL TREND
WETTER AND MORE ACTIVE FRIDAY AND SATURDAY AHEAD OF A SHORTWAVE
MOVING INTO THE REGION, WITH UPPER RIDGING BUILDING BACK IN AFTER.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODEL RUNS CONTINUE TO SHOW MORE FAVORABLE AGREEMENT THAN
THE PAST FEW DAYS WITH THE UPPER LOW IN THE OHIO/TENNESSEE VALLEYS
AND PIVOTING NORTHWARD THROUGH THE INTERIOR NORTHEAST THURSDAY-
FRIDAY, AS THE RESULTING SURFACE LOW MOVES ACROSS THE APPALACHIANS
AND VICINITY. SOME MODEL DIFFERENCES WITH THE TIMING AND TRACK OF
THE LOW AND FRONTS ARE NOW WITHIN MORE TYPICAL SPREAD FOR THE EARLY
MEDIUM RANGE PERIOD. BEHIND THIS, A COUPLE OF SHORTWAVES DROP INTO
THE NORTH-CENTRAL U.S. LATE WEEK AND INTO THE WEEKEND, ACTING TO
REINFORCE TROUGHING OVER THE EAST FOR EARLY NEXT WEEK. MODEL SPREAD
GROWS WITH THESE FEATURES, PARTICULARLY WITH THE AMPLITUDE OF
TROUGHING (06Z GFS ON THE SHALLOWER SIDE) AND ITS TIMING (00Z CMC
BECOMES FAST IN REACHING THE WESTERN ATLANTIC EARLY MONDAY. THE
RESULTING SURFACE LOW IN THE NORTHERN TIER WAS PARTICULARLY STRONG
INTO THE GREAT LAKES IN THE 06Z GFS BY NEXT MONDAY, AND IN GENERAL
THE 12Z MODELS SEEMED TO TREND A LITTLE WEAKER THAN THE PREVIOUS
MODEL CYCLE. THIS PATTERN FOR EASTERN U.S. TROUGHING MAY ALLOW FOR
A COASTAL LOW TO DEVELOP AS WELL, OR AT LEAST SURFACE TROUGHING.
FOR THE WEST, UPPER RIDGING WILL MOSTLY BE IN PLACE TO THE SOUTH
OF A SHORTWAVE MOVING THROUGH THE NORTHWEST AROUND THURSDAY AND
STRONG ZONAL FLOW THEREAFTER. MODELS SHOW GOOD CONSENSUS FOR THIS,
AND THEN WILL HAVE TO CONTINUE TO MONITOR THE PATTERN ACROSS THE
EASTERN PACIFIC BY EARLY NEXT WEEK AS MODEL SPREAD INCREASES.
A GENERAL BLEND OF THE 00/06Z DETERMINISTIC GUIDANCE SERVED AS A
GOOD STARTING POINT FOR THE EARLY PART OF THE MEDIUM RANGE
FORECAST, AND EVEN INTO THE WEEKEND FORECAST WITH THE REASONABLE
LARGE SCALE AGREEMENT. DID INCREASE THE PROPORTION OF ENSEMBLE
MEANS TO AROUND HALF BY DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
REASONABLY STRONG SURFACE LOW PRESSURE SHIFTING FROM THE MID-
ATLANTIC INTO THE NORTHEAST THURSDAY INTO FRIDAY WILL DRAW TROPICAL
ATLANTIC MOISTURE INTO IT, CREATING A THREAT FOR MODERATE TO HEAVY
RAINFALL IN THIS REGION ALONG AND AHEAD OF THE LOW TRACK AND
ASSOCIATED COLD FRONT. WITH MODEST INSTABILITY IN PLACE, AND
SUFFICIENT FORCING AND DIVERGENCE WITHIN THE COUPLED JET IN THE
NEGATIVELY TILTED TROUGH, LOCALLY HEAVY RAIN RATES ARE POSSIBLE
WITH ISOLATED FLOODING CONCERNS. A MARGINAL RISK IS IN PLACE ON THE
DAY 4/THURSDAY ERO OVER PARTS OF THE MID-ATLANTIC AND NORTHEAST.
FROM EXTENSIVE COLLABORATION WITH WFOS, THE MARGINAL RISK WAS
TRIMMED OUT OF AREAS FARTHER INLAND, EVEN THOUGH HEAVY RAIN RATES
MAY REACH PARTS OF INTERIOR NEW YORK AND NEW ENGLAND AND THE
ANTECEDENT DRY GROUND CAN OFTEN ENHANCE RUNOFF. RAIN RATES SHOULD
STAY AT MORE MODERATE LEVELS BACK TOWARD THE LOWER GREAT LAKES
REGION CLOSER TO THE UPPER LOW WHERE THERE WILL BE LESS
INSTABILITY. HEAVY RAIN LOOKS TO BE MOVING THROUGH MAINE FRIDAY
MORNING AND THEN EXITING THE NORTHEAST, THOUGH LAKE EFFECT RAINS
ARE LIKELY BEHIND THE PRIMARY SYSTEM. BY THE WEEKEND, UPPER LEVEL
ENERGY AND FRONTAL SYSTEMS COULD LEAD TO ROUNDS OF LIGHT
PRECIPITATION, PRIMARILY RAIN, IN THE MIDWEST, GREAT LAKES,
OHIO/TENNESSEE VALLEYS, AND POSSIBLY REACHING THE CENTRAL GULF
COAST.
THURSDAY SHOULD BE A RELATIVELY DRY DAY FOR THE PACIFIC NORTHWEST,
BUT RENEWAL OF PRECIPITATION THAT COULD BE HEAVY IS POSSIBLE
FRIDAY INTO SATURDAY AS A MODERATELY STRONG ATMOSPHERIC RIVER TAKES
AIM AT THE REGION AHEAD OF A LARGER NORTHEAST PACIFIC LOW. THE
MARGINAL RISK IN THE DAY 5/FRIDAY ERO STILL LOOKS GOOD FOR THIS
REGION, BUT JUST TRIMMED OUT THE SOUTHERN PART OF THE RISK AREA DUE
TO SLOWER MOVEMENT OF THE AR SOUTHWARD. MOST PRECIPITATION IS
FORECAST TO STAY RAIN OTHER THAN SNOW IN THE HIGHEST PEAKS OF THE
OLYMPICS THROUGH FRIDAY, WITH PERHAPS MORE SNOW IN THE CASCADES.
ELSEWHERE, THE SOUTHWEST TO THE PLAINS SHOULD STAY MOSTLY DRY
THROUGH THE PERIOD UNDER THE RIDGE ALOFT.
THE SOUTHWESTERN U.S. CAN EXPECT WARMER THAN AVERAGE TEMPERATURES
UNDERNEATH UPPER RIDGING FOR MUCH OF THE PERIOD, EXPANDING THROUGH
MUCH OF THE WEST INTO THE CENTRAL U.S. BY THE WEEKEND. THE DESERT
SOUTHWEST CAN EXPECT HIGHS IN THE 90S, AROUND 5-15 DEGREES ABOVE
NORMAL. MEANWHILE, THE SOUTHEASTERN QUADRANT OF THE LOWER 48 SHOULD
SEE BELOW AVERAGE TEMPERATURES LATE THIS WEEK UNDER THE UPPER LOW,
WITH DAYTIME HIGHS ONLY INTO THE UPPER 50S/LOW 60S IN MUCH OF THE
SOUTHEAST AROUND 10-20 DEGREES BELOW AVERAGE. THESE COOL
TEMPERATURES SHOULD MODERATE INTO THE WEEKEND AS THE LOW LIFTS
THROUGH THE EAST, WITH TEMPERATURES RETURNING BACK CLOSER TO NORMAL
BY EARLY NEXT WEEK.
TATE/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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