696
FXUS02 KWBC 270744
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
344 AM EDT SUN SEP 27 2026
VALID 12Z WED SEP 30 2026 - 12Z SUN OCT 04 2026
...MAJOR SOUTH-CENTRAL TO EAST-CENTRAL U.S. HEAVY RAIN/FLOODING
THREAT WITH TROPICAL MOISTURE CONNECTIONS INTO MID-LATER WEEK...
..GUIDANCE/PREDICTABILITY ASSESSMENT
FORECAST SPREAD HAS DECREASED OVER THE PAST FEW CYCLES AND RECENT
GUIDANCE IS NOW SHOWING A REASONABLY SIMILAR LARGER SCALE PATTERN
EVOLUTION THROUGH THESE MEDIUM-RANGE TIME SCALES TO BOLSTER
BROAD THREAT CONFIDENCE, BUT NOT LOCAL FOCUS DETAILS. THIS IS DUE
TO NUMEROUS SMALLER SCALE EMBEDDED SYSTEM TIMING ISSUES AND
SYSTEM/CONVECTION INTERACTIONS. ACCORDINGLY FAVOR A BLEND OF BEST
CLUSTERED GUIDANCE OF THE GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS,
WITH EMPHASIS ON THE MODELS PAST MIDWEEK SLOWLY SHIFTING TO THE
ENSEMBLE MEANS LATER WEEK INTO NEXT WEEKEND IN LINE WITH WITH
UNCERTAINTY GROWTH FOR CONSISTENT THREAT MESSAGING AND PRODUCTS.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
A CLOSED UPPER TROUGH/LOW WITH WAVY FRONTAL SYSTEMS WILL SHIFT
SLOWLY EASTWARD FROM THE SOUTHWEST U.S. TO THE SOUTH-CENTRAL U.S.
MID-LATER WEEK IN SOUTHERN STREAM SPLIT FLOW. EXCESSIVE
RAINFALL/FLOODING THREATS OVER THE SOUTHWEST/SOUTHERN ROCKIES
STATES THROUGH MIDWEEK WILL FOCUS OVER THE SOUTH-CENTRAL U.S. AND
WITH GULF COASTAL FRONTAL GENESIS MID-LATER WEEK INTO NEXT WEEKEND.
THE SIGNIFICANT EPISODE PERIOD WILL BE FUELED BY TROPICAL MOISTURE
CONNECTIONS FROM CURRENT EAST PACIFIC HURRICANE POLO (SET TO
LANDFALL INTO MEXICO) AND ALSO WITH INCREASINGLY DEEP AND SUSTAINED
LEAD GULF INFLOW WITH SOME TROPICAL INFLUENCE. THIS EXPANSIVE
MULTI-DAY THREAT SHOULD PROVE SLOW TO PROGRESS OVER THE EAST-
CENTRAL U.S. LATE WEEK/NEXT WEEKEND BLOCKED BETWEEN UPPER RIDGE
DEVELOPMENTS OVER BOTH THE SOUTHWEST AND SOUTHEAST U.S..
ACCORDINGLY, HUGE WPC EXCESSIVE RAINFALL OUTLOOK (ERO) MARGINAL
RISK AND EMBEDDED SLIGHT RISK THREAT AREAS HAVE BEEN INTRODUCED FOR
DAY 4/WEDNESDAY AND DAY5/THURSDAY OVER THE SOUTH-CENTRAL U.S..
MEANWHILE, SYSTEMS WITHIN A MORE PROGRESSIVE/ZONAL MEAN NORTHERN
STREAM FLOW WILL SUPPORT PASSAGE OF A SERIES OF WAVY FRONTAL
SYSTEMS ACROSS THE U.S. NORTHERN TIER OF THE NATION FROM THE
NORTHWEST THROUGH THE NORTHEAST THIS WEEK. THESE WILL ACT TO
PROVIDE A NORTHERN RAINFALL SHIELD FOCUS FOR LIFTING MOISTURE AND
ALSO DELIVER PERIODS OF MODERATING POST-FRONTAL FALL TEMPERATURES.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page