316
FXUS02 KWBC 090643
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 AM EDT SUN AUG 9 2026
VALID 12Z WED AUG 12 2026 - 12Z SUN AUG 16 2026
...MULTI-DAY HEAVY RAINFALL THREAT EXTENDING FROM PARTS OF THE
MID- MISSISSIPPI VALLEY TO OHIO VALLEY NEXT WEEK...
...HAZARDOUS HEAT BUILDS ACROSS MUCH OF THE SOUTH-CENTRAL AND
SOUTHEAST U.S. THROUGH THE END OF NEXT WEEK...
..OVERVIEW
A PROGRESSIVE AND UNSETTLED REGIME ACROSS THE NORTHERN AND EASTERN
U.S. AND RIDGING OVER SOUTH-CENTRAL U.S. WILL CONTINUE INTO LATE
WEEK. THE UPPER RIDGE WILL BRING HAZARDOUS HEAT ACROSS THE
SOUTHEAST AND SOUTHERN PLAINS THROUGH SATURDAY. THE SHORTWAVE
EMBEDDED IN THE AMPLIFIED FLOW WILL SUPPORT THUNDERSTORMS AND
SHOWERS ACROSS THE NORTHERN TIER. MULTIPLE DAYS OF SLOW-MOVING
STORMS ACROSS PORTIONS OF MID-MISSISSIPPI AND OHIO VALLEY MAY LEAD
TO FLOODING CONCERNS. TROUGHING OVER THE WEST COAST/PACIFIC
NORTHWEST WILL REINFORCE SHOWERS AND THUNDERSTORMS ACTIVITY
STRETCHING ACROSS THE SOUTHWEST AND INTERMOUNTAIN WEST/GREAT
BASIN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LARGE-SCALE PATTERN IS REASONABLY WELL ESTABLISHED THROUGH THE
FIRST HALF OF THE PERIOD, WITH GOOD AGREEMENT AMONG THE LATEST
DETERMINISTIC AND ENSEMBLE GUIDANCE ON THE PERSISTENCE OF AN
ACTIVE NORTHERN- TIER FLOW AND RIDGING OVER THE SOUTH-CENTRAL U.S.
CONFIDENCE DECREASES WITH TIME CONCERNING THE AMPLITUDE AND EXACT
PLACEMENT OF SHORTWAVE TROUGHS CROSSING THE NORTHERN CONUS, WHICH
WILL IMPACT THE PLACEMENT OF FRONTAL BOUNDARIES AND AREAS OF HEAVY
RAINFALL. THE GFS CONTINUES TO REMAIN A OUTLIER WITH SOME OF THE
SMALL-SCALE FEATURES THAT IMPACT THE RAINFALL ACROSS EASTERN U.S.
FOR THE FORECAST, A PREFERENCE TOWARDS A MULTI-MODEL BLEND FOR THE
FIRST PORTION OF THE PERIOD WAS USED, WHILE INCORPORATING A HEAVIER
WEIGHT ON THE ENSEMBLE MEANS BY DAY 5.
..WEATHER/HAZARDS HIGHLIGHTS
ACROSS THE NORTHERN TIER A SERIES OF SHORTWAVE ENERGIES WILL EJECT
EASTWARD INTO THE BROAD TROUGHING OVER EASTERN U.S. THROUGH THE
PERIOD. THIS WILL PROMOTE UNSETTLED WEATHER AS THE ASSOCIATED SLOW
MOVING FRONTAL BOUNDARY DRAPES ACROSS PORTIONS OF THE
ROCKIES/PLAINS INTO THE GREAT LAKES/OHIO VALLEY AND ACROSS THE
NORTHEAST. THE WARM AND MOIST AIR MASS AHEAD OF THESE DISTURBANCES
WILL SUPPORT SUFFICIENT INSTABILITY AND LIFT FOR ORGANIZED
CLUSTERS, ESPECIALLY OVER THE OHIO VALLEY/MID-ATLANTIC INTO
PORTIONS OF THE NORTHEAST. HIGH RAIN RATES FROM THE SLOW MOVING
STORMS MAY LEAD TO FLASH FLOODING CONCERNS, WHICH IS HIGHLIGHTED IN
THE DAY 4 AND 5 EXCESSIVE RAINFALL OUTLOOKS (ERO). THE ERO SHOWS A
BROAD MARGINAL RISK ACROSS THE NORTHERN/CENTRAL PLAINS/ROCKIES
INTO THE MID-MISSISSPPI VALLEY, OHIO VALLEY/TENNESSEE VALLEY, AND
PORTIONS OF THE SOUTHEAST, WITH A SLIGHT RISK OVER PORTIONS OF THE
OHIO VALLEY/MID-ATLANTIC (FOR WEDNESDAY/DAY 4) AND MID-MISSISSPPI
VALLEY (FOR THURSDAY/DAY 5).
FOR THE REMAINDER OF THE WEEK INTO THE WEEKEND, THE SURFACE LOW
AND ASSOCIATED STATIONARY FRONT WILL LINGER OVER THE HIGH PLAINS
AND CENTRAL U.S. AS SUFFICIENT MOISTURE ACCUMULATES ALONG THE
BOUNDARY AND INSTABILITY INCREASES, DAILY THUNDERSTORM CHANCES WILL
CONTINUE. WITH THE POTENTIAL FOR ORGANIZED CONVECTION TO DEVELOP
AS SHORTWAVES ENERGY, THE FLASH FLOODING CONCERNS MAY CONTINUE.
ACROSS THE SOUTHWEST, AN ACTIVE CONVECTIVE PATTERN CONTINUES AS
THE RIDGING WEAKENS BY MIDWEEK AND MONSOONAL MOISTURE CONTINUES TO
PRODUCE THUNDERSTORMS THROUGH THE WEEK. WITH CHANCES FOR MULTIPLE
DAYS OF REPEATED SHOWERS AND THUNDERSTORMS, FLASH FLOODING CONCERNS
WILL INCREASE ACROSS PORTIONS OF THE SOUTHWEST, ROCKIES, INTERIOR
CALIFORNIA, AND GREAT BASIN, ESPECIALLY OVER BURN SCARS, URBAN
AREAS, SLOT CANYONS, AND STEEP TERRAIN.
THE RIDGE OVER SOUTHWEST WILL CONTINUE TO MOVE EASTWARD THROUGH THE
WEEK, BRINGING HAZARDOUS HEAT ACROSS THE SOUTHEAST, GULF COAST, AND
PORTIONS OF THE SOUTHERN PLAINS. WITH HIGH HUMIDITY FROM THE GULF,
HEAT INDICES MAY BECOME OPPRESSIVE AS WIDESPREAD MAJOR HEATRISK
WITH LOCALLY EXTREME HEATRISK LEVELS SPREADS ACROSS MUCH OF THE
AREA. PORTIONS OF THE SOUTHERN PLAINS WILL SEE HIGHS IN THE LOW
100S, WHILE THE SOUTHEAST WILL SEE MID TO UPPER 90S. HEAT- RELATED
IMPACTS COULD BECOME SIGNIFICANT WHERE THE COMBINATION OF HIGH
TEMPERATURES AND HUMIDITY PERSIST FOR SEVERAL CONSECUTIVE DAYS.
OUDIT
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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