813
FXUS02 KWBC 101836
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT FRI OCT 10 2025
VALID 12Z MON OCT 13 2025 - 12Z FRI OCT 17 2025
...STRONG COASTAL LOW WITH SIGNIFICANT COASTAL FLOODING, BEACH
IMPACTS, HIGH WINDS AND HEAVY RAIN LINGERS FOR THE EAST COAST...
...HEAVY RAIN AND FLASH FLOODING REMAIN A THREAT FOR THE SOUTHWEST
EARLY NEXT WEEK GIVEN ANOMALOUS TROPICAL EAST PACIFIC MOISTURE...
..CALIFORNIA HEAVY RAIN THREAT WITH EARLY NEXT WEEK CLOSED LOW
..OVERVIEW
A POTENT COASTAL STORM IS FORECAST TO CONTINUE TO LIFT SLOWLY
NORTHWARD UP THE EAST COAST INTO EARLY NEXT WEEK. THIS COASTAL LOW
MAY BRING STRONG ONSHORE WINDS CAUSING COASTAL FLOODING, RIP
CURRENTS, BEACH EROSION, AND HEAVY RAIN TO THE MID-ATLANTIC AND
NORTHEAST. MEANWHILE, UPPER TROUGHING IN THE WEST WILL DRAW
TROPICAL MOISTURE AND REMNANT TROPICAL ENERGY NORTHWARD AND BRING
POTENTIALLY WIDESPREAD HEAVY RAIN AND SOME FLASH FLOODING INTO THE
SOUTHWEST EARLY NEXT WEEK. THIS TROUGH AND ANOTHER ROUND WITH A
CLOSED LOW/TROUGH INTO THE WEST WILL MAINTAIN COOLER THAN AVERAGE
TEMPERATURES AS WELL AS HEAVY PRECIPITATION CHANCES WITH FOCUS OVER
CALIFORNIA TO INCLUDE HIGHER ELEVATION SIERRA SNOWS. UPPER RIDGING
SHOULD PREVAIL FARTHER EAST IN THE CENTRAL U.S., ALLOWING FOR
UNSEASONABLY WARM TEMPERATURES, AND ROUNDS OF RAIN IN THE NORTH-
CENTRAL U.S. DIRECTED AROUND THE RIDGE MAY INCREASE LATER NEXT
WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE TODAY REMAINS IN OVERALL GOOD AGREEMENT ON THE
LARGER SCALE PATTERN EVOLUTION DURING THE MEDIUM RANGE PERIOD BUT
STILL WITH CONSIDERABLE UNCERTAINTY IN THE DETAILS. THERE IS BETTER
CONSENSUS FOR THE TRACK AND TIMING OF THE COASTAL LOW UP THE MID-
ATLANTIC/NORTHEAST COAST BY MONDAY, BUT DIFFERENCES IN HOW CLOSE
THAT LOW TRACKS TO THE COAST HAVE IMPORTANT IMPLICATIONS FOR INLAND
EXTEND OF HEAVIER RAINFALL. OUT WEST, A DEEP UPPER LOW WILL DROP
DOWN THE CA COAST AND EVENTUALLY SHIFT INLAND WITH SOME UNCERTAINTY
IN THE TIMING OF THAT. THE 06Z GFS WAS AN OUTLIER LATE PERIOD
SEEMINGLY STEMMING FROM THE EVOLUTION OF A SHORTWAVE INTO THE GREAT
LAKES REGION AND ITS DOWNSTREAM IMPACTS ON THE REST OF THE PATTERN
ACROSS THE CONUS. THE WPC FORECAST USED A DETERMINISTIC MODEL
BLEND FOR DAYS 3 AND 4, LEANING HEAVIER ON THE ECMWF AND CMC WITH
THE ENSEMBLE MEANS THEREAFTER. THIS ALSO MAINTAINED GOOD AGREEMENT
WITH THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A DANGEROUS COASTAL STORM WILL OFFER A WIDE ARRAY OF THREATS UP
THE EAST COAST INTO EARLY NEXT WEEK. BY TUESDAY, THE MAIN HEAVY
RAIN THREAT SHOULD FOCUS MORE FROM COASTAL MID- ATLANTIC TO LONG
ISLAND AND COASTAL NEW ENGLAND. THERE REMAINS AMPLE UNCERTAINTY
WITH THE INLAND EXTENT OF RAIN AMOUNTS GIVEN AN UNCERTAIN COASTAL
STORM EVOLUTION AND EJECTION. THERE COULD BE POTENTIAL HEAVY BANDS
OF RAIN, WHICH COMBINED WITH ANY URBAN AREA COULD ENHANCE FLOODING
ISSUES. GIVEN THE UNCERTAINTY OPTED TO MAINTAIN A WPC DAY 4/TUESDAY
MARGINAL RISK FOR THE COASTAL MID-ATLANTIC TO NORTHEAST. IN
ADDITION TO HEAVY RAIN THREATS, THE COMBINATION OF PERSISTENT AND
STRONG ONSHORE WINDS, HIGH SURF, AND ABOVE NORMAL TIDES MAY LEAD TO
SIGNIFICANT COASTAL FLOODING IMPACTS ALONG WITH STRONG RIP
CURRENTS AND POTENTIAL BEACH EROSION. SEE KEY MESSAGES BEING ISSUED
BY WPC FOR THE LATEST ON THIS SYSTEM. THE SYSTEM SHOULD PULL AWAY
FROM THE COAST BY TUESDAY OR WEDNESDAY.
EARLY NEXT WEEK, ANOTHER ROUND OF TROPICAL MOISTURE AND ENERGY IS
FORECAST TO ENTER THE SOUTHWEST AS NEWLY FORMED RAYMOND IN THE
PACIFIC FOLLOWS IN THE WAKE OF PRISCILLA. PRECIPITABLE WATER VALUES
ARE LIKELY TO BE NEAR MAX VALUES FOR THIS TIME OF YEAR, WITH THE
SOUTHWEST ALSO IN THE RIGHT ENTRANCE REGION OF THE UPPER JET FOR
GOOD DYNAMICAL SUPPORT FOR HEAVY RAIN. HOWEVER, A LIMITING FACTOR
IN TERMS OF FLASH FLOODING COULD BE SOMEWHAT LIMITED INSTABILITY
UNDER WIDESPREAD CLOUDS AND RAIN, WHICH COULD LIMIT RAIN RATES.
ALSO, THE CURRENT FORECAST SHOWS THE GREATEST RAINFALL TOTALS TO
THE SOUTHEAST OF WHERE THE HEAVIEST RAIN COULD FALL IN THE SHORT
RANGE. THUS CONTINUE TO HOLD OFF ON ANY MODERATE RISKS AT THIS
TIME, BUT A SLIGHT RISK IS IN PLACE ACROSS PORTIONS OF ARIZONA AND
NEW MEXICO FOR THE DAY 4/MONDAY EXCESSIVE RAINFALL OUTLOOK.
ELSEWHERE, A MOISTURE PLUME/ATMOSPHERIC RIVER IS FORECAST TO SHIFT
SOUTHWARD ACROSS CALIFORNIA EARLY NEXT WEEK AHEAD OF A COLD FRONT
TO PRODUCE HEAVY RAINFALL AND MOUNTAIN SNOWS FOR CALIFORNIA. WHILE
IT COULD BE RELATIVELY FAST- MOVING, SOME INSTABILITY COULD BE
PRESENT AND RAINFALL RATES COULD REACH AN INCH PER HOUR, SO HAVE A
MARGINAL RISK OF EXCESSIVE RAINFALL FOR PARTS OF CALIFORNIA FOR THE
WPC DAY 4/5 EROS CENTERED ON MONDAY/TUESDAY. LIGHTER MOUNTAIN SNOW
WILL ALSO SPREAD ACROSS THE INTERMOUNTAIN WEST AND ROCKIES
ASSOCIATED WITH THE AMPLIFIED UPPER TROUGHING. FARTHER EAST, ROUNDS
OF PRECIPITATION ARE POSSIBLE IN THE PLAINS TO UPPER MIDWEST AND
GREAT LAKES REGION WITH DOWNSTREAM SYSTEM/ENERGY TRANSLATIONS NEXT
WEEK OUT FROM THE WEST/ROCKIES AS LEAD MOISTURE AND INSTABILITY
POOL WITH GENESIS OF SEVERAL WAVY FRONTAL SYSTEMS ON THE NORTHERN
PERIPHERY OF A WARMING SOUTH- CENTRAL U.S. UPPER RIDGE.
IT STILL REMAINS GENERALLY THE CASE THAT COOLER THAN AVERAGE
TEMPERATURES ARE FORECAST PARTICULARLY FOR HIGHS IN THE WEST
THROUGH NEXT WEEK UNDERNEATH RENEWING TROUGHING. MEANWHILE, UPPER
RIDGING IN THE CENTRAL U.S. WILL LEAD TO WARMER THAN AVERAGE
TEMPERATURES. HIGHS IN THE 70S REACHING AS FAR NORTH AS THE DAKOTAS
SUNDAY WILL BE 15-20 DEGREES ABOVE AVERAGE. TEMPERATURES THERE
SHOULD COOL BEHIND A COLD FRONT INTO THE WORKWEEK, BUT TEMPERATURES
OF 10 TO 15 DEGREES ABOVE NORMAL WILL LAST SEVERAL DAYS FARTHER
SOUTH, AS UNSEASONABLY WARM HIGHS IN THE 90S CONTINUE FOR TEXAS AND
LOUISIANA. WARMER THAN AVERAGE TEMPERATURES ARE FORECAST TO
STRETCH INTO THE MIDWEST. SOME COOL HIGHS ALONG THE EAST COAST
EARLY WEEK SHOULD MODERATE CLOSE TO NORMAL AS THE WEEK PROGRESSES.
SANTORELLI/SCHICHTEL
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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