118
FXUS02 KWBC 220734
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
334 AM 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 AND HIGH SURF, AND
POTENTIAL BEACH EROSION. AN UPPER RIDGE PERSISTING IN THE SOUTH-
CENTRAL U.S. WILL PROMOTE WARM TEMPERATURES, WHILE A COUPLE OF
UPPER TROUGHS COME INTO THE NORTHWESTERN AND NORTH-CENTRAL U.S.
THROUGH THE PERIOD AND BRING ROUNDS OF PRECIPITATION TO THOSE
REGIONS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO AGREE THAT A COASTAL LOW WILL BE IN THE WESTERN
ATLANTIC FRIDAY INTO THE WEEKEND UNDERNEATH A STALLING UPPER LOW.
THE SURFACE LOW SHOULD BE RATHER DEEP, REACHING THE 980S OR AT
LEAST 990S (MB) AROUND SATURDAY. THE LOW WILL LIKELY BE PRETTY
STACKED AND SEEMS TO BE WARM CORE PER PHASE SPACE DIAGRAMS,
INDICATING THERE COULD BE A WARM SECLUSION AND/OR HAVE SOME
SUBTROPICAL CHARACTERISTICS. ITS POSITION FROM DAY TO DAY AT IT
MEANDERS IS MUCH MORE UNCERTAIN. THE EC AND UKMET DEVELOP THE LOW
FARTHER SOUTH IN THE ATLANTIC FRIDAY-SATURDAY AND REACH NEAR LONG
ISLAND BY SUNDAY, COMPARED TO THE FARTHER NORTHEAST GFS/AIGFS/CMC,
WITH THE EC-AIFS LOOKING LIKE A REASONABLE MIDDLE GROUND LIKE THE
EC MEAN. BY MONDAY-TUESDAY THE LOW SHOULD BE WEAKER BUT WITH
REMAINING QUESTIONS ON WHEN IT PULLS AWAY. ALL IN ALL THERE IS
STILL AMPLE SPREAD WITH THE DETAILS, WHICH COULD HAVE SENSIBLE
WEATHER IMPACTS LIKE WIND SPEED/DIRECTION AND HOW MUCH RAIN FALLS
ONSHORE OR 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. WILL
ALSO MENTION THAT HURRICANE POLO IN THE EASTERN PACIFIC STILL HAS
SOME MODEL SPREAD IN ITS TRACK, BUT NUMBER OF MODELS/ENSEMBLE
MEMBERS ARE DECREASING FOR HAVING IT CURVE INTO BAJA CALIFORNIA.
POLO'S TRACK WILL AFFECT POTENTIAL MOISTURE INFLOW INTO THE
SOUTHWEST.
THE WPC FORECAST USED A MODEL AND ENSEMBLE BLEND EVEN EARLY IN THE
FORECAST PERIOD, GIVEN THE SPREAD WITH THE EASTERN LOW. INCREASED
THE PROPORTION OF ENSEMBLE MEANS TO WELL OVER HALF BY DAYS 6-7 TO
MITIGATE THE INDIVIDUAL MODEL DIFFERENCES IN THE DETAILS OF THE
PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
THE SURFACE LOW IN THE WESTERN ATLANTIC MEANDERING 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 CURRENT
FORECAST SUPPORTS 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 BY MONDAY 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
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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