278
FXUS02 KWBC 222000
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT TUE SEP 22 2026
VALID 12Z FRI SEP 25 2026 - 12Z TUE SEP 29 2026
...IMPACTFUL COASTAL STORM MEANDERS NEAR THE MID-ATLANTIC AND NORTHEAST
LATE WEEK/WEEKEND...
..OVERVIEW
AN UPPER LOW WILL STALL ATOP THE MID-ATLANTIC AND NORTHEAST LATE
WEEK INTO THE WEEKEND, SUPPORTING A MEANDERING COASTAL SURFACE LOW.
THIS PATTERN WILL LEAD TO STRONG/GUSTY ONSHORE WINDS FOR MULTIPLE
DAYS, LEADING TO COASTAL FLOODING, RIP CURRENTS, HIGH SURF, AND
POTENTIAL BEACH EROSION. MEANWHILE, AN UPPER RIDGE PERSISTING IN
THE SOUTH-CENTRAL U.S. WILL PROMOTE WARM TEMPERATURES, WHILE A
COUPLE OF UPPER TROUGHS BRING ROUNDS OF PRECIPITATION TO PARTS OF
THE NORTHWESTERN AND NORTH-CENTRAL U.S. THROUGH THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO HAVE A DECENT HANDLE ON THE OVERALL LARGE SCALE
PATTERN THROUGH MOST OF THE MEDIUM RANGE PERIOD, THOUGH SOME
UNCERTAINTY REMAINS WITH SMALLER SCALE DETAILS. CASE IN POINT,
THERE IS STILL A FAIR AMOUNT OF SPREAD WITH COASTAL LOW DEVELOPMENT
IN THE WESTERN ATLANTIC LATE WEEK INTO THE WEEKEND UNDERNEATH A
STALLING UPPER LOW. THE EC AND ESPECIALLY THE UKMET DEVELOP THE LOW
FARTHER SOUTH IN THE ATLANTIC FRIDAY-SATURDAY, COMPARED WITH MOST
OTHER GUIDANCE SOURCES WHICH ARE FARTHER NORTH AND EAST. THE EC
CONTINUES TO DEPICT A TRACK THAT REACHES NEAR LONG ISLAND OR THE
JERSEY SHORE BY SUNDAY, WHILE THE FARTHER NORTHEAST
GFS/AIGFS/CMC/ICON TRACK THE LOW JUST OFF THE COAST OF NEW ENGLAND.
THE EC-AIFS, WHICH WAS A REASONABLE MIDDLE GROUND IN THE PREVIOUS
FORECAST, LOOKS MORE LIKE THE EC FOR ITS 12Z RUN. BY MONDAY-TUESDAY
THE LOW SHOULD BE WEAKER BUT WITH REMAINING QUESTIONS ON WHEN IT
PULLS AWAY AND FROM WHERE. GIVEN THERE IS STILL AMPLE SPREAD
BETWEEN TWO DISTINCT CAMPS, QUESTIONS REMAIN WITH RESPECT TO
SENSIBLE WEATHER IMPACTS LIKE WIND SPEED/DIRECTION AND HOW MUCH
RAIN FALLS ONSHORE VS. OFFSHORE.
ELSEWHERE, GUIDANCE SHOWS GOOD CONSENSUS ON THE UPPER RIDGE IN THE
SOUTH-CENTRAL U.S., THOUGH VARYING POSITIONS OF WEAK FRONTS AND
PRECIPITATION POTENTIAL CAUSE UNCERTAINTIES IN THE TEMPERATURES.
THE RIDGE LOOKS TO EXTEND NORTH AND TRAVERSE THE MIDWEST/GREAT
LAKES FRIDAY AND OVER THE WEEKEND, CONTRIBUTING TO THE BLOCKY
PATTERN AS IT STRETCHES INTO SOUTHEAST CANADA NORTH OF THE ATLANTIC
UPPER LOW. MEANWHILE A COUPLE OF TROUGH AXES WILL TRACK ACROSS THE
NORTHWESTERN TO NORTH-CENTRAL U.S. WITH TYPICAL SPREAD IN THEIR
TIMING AND DEPTH. GUIDANCE GENERALLY SHOWS ONE CROSSING THE PACIFIC
NORTHWEST AT THE START OF THE PERIOD FRIDAY, TRACKING ACROSS THE
NORTHERN TIER AND LIFTING INTO CENTRAL CANADA ON SUNDAY. THEN AN
UPSTREAM TROUGH IS FORECAST TO MOVE INTO THE WEST COAST SUNDAY AND
CONTINUE TRACKING EAST. BY MONDAY INTO TUESDAY MODELS SHOW VARYING
DEGREES OF STREAM SEPARATION THAT AFFECTS THE TROUGH'S TIMING.
MEANWHILE, HURRICANE POLO IN THE EASTERN PACIFIC HAS RAPIDLY
INTENSIFIED INTO A CATEGORY 5 HURRICANE TODAY, WITH CONTINUED
MONITORING FOR DOWNSTREAM IMPACTS LATER IN THE PERIOD. HOWEVER,
DESPITE POLO STILL HAVING SOME MODEL SPREAD IN ITS TRACK, THE
NUMBER OF MODELS/ENSEMBLE MEMBERS DEPICTING A CURVE INTO BAJA
CALIFORNIA ARE RAPIDLY DECREASING. A MORE SUPPRESSED TRACK WOULD
ULTIMATELY LIMIT THE AMOUNT OF MOISTURE THAT COULD BE DRAWN
NORTHWARD INTO THE SOUTHWEST AS A RESULT.
THE WPC FORECAST USED A DETERMINISTIC AND AI MODEL BLEND EARLY IN
THE FORECAST PERIOD, THEN INCORPORATED MORE ENSEMBLE MEANS AND
INCREASED THE WEIGHTING OF SAID MEANS TO 50 PERCENT BY DAYS 6-7 TO
MITIGATE THE INDIVIDUAL MODEL DIFFERENCES IN THE DETAILS OF THE
PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
THE MEANDERING SURFACE LOW IN THE WESTERN ATLANTIC WILL LEAD TO
BROAD ONSHORE FLOW ACROSS THE MID-ATLANTIC AND NORTHEAST FOR
MULTIPLE DAYS. THIS PERSISTENT PATTERN COULD LEAD TO COASTAL
FLOODING AND BEACH EROSION CONCERNS, ESPECIALLY WHEN COMBINED WITH
HIGH ASTRONOMICAL TIDES. EXACT PLACEMENT OF THE SURFACE LOW FROM
DAY TO DAY AND THUS ANY HEAVY RAIN IS MORE UNCERTAIN. THE LATEST
FORECAST CONTINUES TO OFFER SUPPORT THAT COASTAL NEW ENGLAND MAY
SEE HEAVY RAINFALL ON FRIDAY INTO THE WEEKEND. HOWEVER, STAY TUNED
FOR FORECAST UPDATES, AS SMALL SHIFTS IN THE LOW TRACK WOULD LEAD
TO SIGNIFICANT FORECAST SHIFTS IN RAINFALL AMOUNTS. SEE WPC'S KEY
MESSAGES FOR THIS COASTAL LOW FOR FURTHER INFORMATION.
PACIFIC MOISTURE IS FORECAST TO ADVECT AROUND THE WESTERN SIDE OF
THE SOUTH-CENTRAL U.S. UPPER RIDGE AND LEAD TO SOME RAIN ACROSS
PARTS OF THE CENTRAL U.S. ON FRIDAY. IF/WHERE ADDITIONAL RAIN FALLS
IN NEW MEXICO, THERE COULD BE FLOODING CONCERNS AFTER THE FORECAST
HEAVY RAINFALL EVENT IN THE SHORT RANGE CAUSES VERY WET ANTECEDENT
CONDITIONS. MEANWHILE FARTHER EAST AND NORTHEAST INTO THE PLAINS,
MODERATE TO LOCALLY HEAVY RAINFALL MAY BE POSSIBLE, BUT ON LESS
SENSITIVE GROUND. RAIN CHANCES PERSIST IN THE UPPER/MIDDLE
MISSISSIPPI VALLEY INTO SATURDAY. MEANWHILE, UPPER TROUGHING WILL
BRING PRECIPITATION TO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES,
INCLUDING HIGHER ELEVATION SNOW CHANCES, ON FRIDAY. SCATTERED
SHOWERS AND THUNDERSTORMS ARE AGAIN POSSIBLE IN PARTS OF THE
PLAINS/MISSISSIPPI VALLEY ON SUNDAY, BUT A MORE WIDESPREAD RAINY
PATTERN WITH POTENTIALLY HEAVIER AMOUNTS IS POSSIBLE MONDAY INTO
TUESDAY AS PACIFIC AND GULF MOISTURE COMBINE AND STREAM INTO THE
CENTRAL U.S. AHEAD OF TROUGHING IN THE WEST.
TEMPERATURES ARE FORECAST TO REMAIN COOLER THAN AVERAGE BY 5-10
DEGREES IN THE MID-ATLANTIC AND NORTHEAST INTO THE WEEKEND
UNDERNEATH THE UPPER LOW, AND HIGHS WILL GENERALLY BE IN THE 60S.
ON THE OTHER HAND, BROAD UPPER RIDGING OVER THE SOUTH-CENTRAL U.S.
COULD MAINTAIN HIGHS IN THE 90S FOR THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY. COOLER THAN NORMAL TEMPERATURES ARE LIKELY IN
THE NORTHWEST GIVEN TROUGHING ALOFT, WHICH SHOULD PUSH INTO THE
NORTHERN ROCKIES/HIGH PLAINS AFTER A WARMER THAN AVERAGE PERIOD
INTO FRIDAY.
TATE/MILLER
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES
ARE AT:
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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