396
FXUS02 KWBC 200729
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
329 AM EDT SUN SEP 20 2026
VALID 12Z WED SEP 23 2026 - 12Z SUN SEP 27 2026
..MONSOON FLOODING THREAT FOR THE SOUTHERN HIGH PLAINS/ROCKIES
..MID-ATLANTIC/NORTHEAST CLOSED UPPER LOW/COASTAL STORM THREAT
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE FORECAST SPREAD HAS IMPROVED TO BOLSTER CONFIDENCE. THE
PATTERN EVOLUTION INTO AUTUMN WILL BE QUITE AMPLIFIED/BLOCKY AS
HIGHLIGHTED BY COOLING/UNSETTING/WET UPPER TROUGHS AND SURFACE
SYSTEMS OVER THE NORTHWEST AND ESPECIALLY THE EAST THAT SANDWICH
A SOUTHERN TIER/CENTRAL U.S. MEAN UPPER RIDGE. A MULTI- MODEL AND
ENSEMBLE MEAN/MACHINE LEARNING GUIDANCE COMPOSITE BLEND SEEMS TO
PROVIDE A GOOD FORECAST BASIS FOR CONSISTENT THREAT MESSAGING,
MAINLY IN LINE WITH WEATHER PARAMETER FORECASTS OF THE NATIONAL
BLEND OF MODELS. WPC PRODUCT CONTINUITY IS WELL MAINTAINED.
..WEATHER/HAZARDS HIGHLIGHTS
UPPER-LEVEL SUPPORT AND A SURFACE FRONTAL SYSTEM WITH A DEVELOPING
COASTAL LOW WILL LEAD TO MULTIPLE ROUNDS OF MODERATE TO HEAVY RAIN
IN THE EAST THIS WEEK. GENERALLY THE APPALACHIANS TO MID-ATLANTIC
COULD SEE HEAVY RAIN THROUGH MIDWEEK, TRANSITIONING TO THE
NORTHEAST LATE WEEK WITH SLOWED COASTAL STORM NORTHWARD TRACK. A
WPC EXCESSIVE RAINFALL OUTLOOK (LINKED BELOW) MARGINAL RISK AREA IS
DEPICTED OVER THE CENTRAL APPALACHIANS/MID-ATLANTIC WEDNESDAY. A
RELATIVELY STRONG SURFACE HIGH FOR SEPTEMBER SHOULD SET UP OVER
QUEBEC AND SPILL A COLD AIR DAMMING WEDGE SOUTH BEHIND THE FRONT,
YIELDING COLDER THAN AVERAGE TEMPERATURES ACROSS THE NORTHEAST/MID-
ATLANTIC, WITH HIGHS GENERALLY IN THE 60S AND UPPER 50S WEDNESDAY-
THURSDAY. THIS PATTERN SUPPORTS STRONG/GUSTY ONSHORE WINDS AND A
CONCERN FOR COASTAL FLOODING FOR THE NORTHEAST AND MID-ATLANTIC.
PACIFIC (INCLUDING POTENTIAL TROPICAL MOISTURE CONNECTION) AND
GULF MOISTURE ARE FORECAST TO COMBINE INTO THE SOUTHWEST NEXT
WEEK. RAIN AMOUNTS MAY BECOME HEAVY IN NEW MEXICO IN PARTICULAR,
AND FLOODING WILL BE POSSIBLE. A MARGINAL RISK AREA ERO IS IN
PLACE WEDNESDAY AND THURSDAY ALONG WITH AN EMBEDDED SLIGHT RISK
AREA WEDNESDAY. RAIN CHANCES WILL EXTEND NORTH ACROSS THE ROCKIES
TO THE HIGH PLAINS AND INTO THE PLAINS WEDNESDAY-FRIDAY.
ELSEWHERE, A WET PATTERN WILL REMAIN IN PLACE ACROSS FLORIDA
THROUGH THE PERIOD, PARTICULARLY FOR SOUTHERN PORTIONS OF THE
PENINSULA AND THE KEYS. MEANWHILE, HAZARDOUS HEAT IS FORECAST TO
LINGER ACROSS TEXAS/WEST GULF COAST THROUGH NEXT MIDWEEK, BUT THEN
GRADUALLY MODERATE AS THE WEEK PROGRESSES. MEANWHILE, INCREASINGLY
BLOCKY/AMPLIFIED FLOW OVER/NEAR THE LOWER 48 WILL INCLUDE
DEVELOPMENT OF A UNSETTLING/WET NORTHWEST U.S. MEAN UPPER TROUGH.
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, 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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