511
FXUS02 KWBC 100640
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 AM EDT MON AUG 10 2026
VALID 12Z THU AUG 13 2026 - 12Z MON AUG 17 2026
...MULTI-DAY HEAVY RAINFALL THREAT EXTENDING FROM PARTS OF THE
MIDWEST TO THE OHIO VALLEY THIS WEEK INTO THE WEEKEND...
...HAZARDOUS HEAT FORECAST ACROSS MUCH OF THE SOUTH-CENTRAL AND
SOUTHEAST U.S. THROUGH NEXT WEEKEND...
..OVERVIEW
A PROGRESSIVE REGIME ACROSS NORTHERN AND EASTERN U.S. AND THE
RIDGING OVER SOUTH-CENTRAL U.S. WILL CONTINUE TO BRING A ACTIVE
PATTERN THROUGH THE WEEKEND INTO NEXT WEEK. THE RIDGE WILL MAINTAIN
HOT CONDITIONS THAT CAN POTENTIAL BECOME HAZARDOUS ACROSS THE
SOUTHERN PLAINS AND SOUTHEAST. MULTIPLE SHORTWAVES WILL EJECT
WITHIN THE AMPLIFIED NORTHERN FLOW, WHICH WILL SUPPORT
THUNDERSTORMS AND SHOWERS ACROSS THE NORTHERN TIER. SEVERAL DAYS OF
REPEATED RAINFALL WILL BRING 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 LATEST DETERMINISTIC AND ENSEMBLE GUIDANCE CONTINUES TO SHOW
GOOD AGREEMENT ON THE OVERALL SYNOPTIC PATTERN, INCLUDING THE
PERSISTENCE OF THE SOUTHERN U.S. RIDGE AND AN ACTIVE NORTHERN
STREAM REGIME. CONFIDENCE IS COMPARATIVELY HIGHER THROUGH THURSDAY
AND FRIDAY, WHILE UNCERTAINTY INCREASES INTO THE WEEKEND AS
INDIVIDUAL SHORTWAVES BECOME INCREASINGLY DIFFICULT TO RESOLVE.
THIS WILL LEAD TO CHALLENGES WITH FORECASTING THE AMPLITUDE AND
TIMING OF SMALL-SCALE FEATURES THAT MAY IMPACT FRONTAL BOUNDARIES
AND SENSIBLE WEATHER. THE ENSEMBLE GUIDANCE SEEMS TO ALLEVIATE
SOME OF THESE CHALLENGES. THEREFORE, A MULTI-MODEL APPROACH
THROUGH THE EARLIER PORTION OF THE PERIOD WERE INCORPORATED IN THE
FORECAST, WHILE PHASING IN THE ENSEMBLE MEANS BY THE WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
A PROGRESSIVE NORTHERN-STREAM FLOW PERSIST ACROSS THE NORTHERN TIER
AND EASTERN U.S. MULTIPLE SHORTWAVE DISTURBANCES WILL TRAVERSE THE
NORTHERN TIER THROUGH THE WEEKEND, AND WILL INTERACT WITH A SLOW-
MOVING FRONTAL ZONE EXTENDING FROM THE NORTHERN/CENTRAL ROCKIES
INTO THE CENTRAL PLAINS, MIDWEST, OHIO VALLEY, AND EVENTUALLY
ACROSS THE GREAT LAKES AND NORTHEAST. THE COMBINATION OF RICH LOW-
LEVEL MOISTURE, INSTABILITY AND REPEATED FORCING ALONG THE
BOUNDARY WILL SUPPORT PERIODIC CLUSTERS OF SHOWERS AND
THUNDERSTORMS, WITH LOCALLY HEAVY RAINFALL AND FLOODING CONCERNS.
WITH THE POTENTIAL FOR LOCALLY INTENSE RAINFALL RATES AND SLOW
MOVING STORMS REDEVELOPING OVER THE SAME AREA, A BROAD MARGINAL
RISK HAS BEEN HIGHLIGHTED IN DAY 4 (THURSDAY) EXCESSIVE RAINFALL
OUTLOOK (ERO) ACROSS PORTIONS OF THE CENTRAL PLAINS INTO MID-
MISSISSIPPI VALLEY, AND OHIO/TENNESSEE VALLEY, WHILE A SLIGHT RISK
HIGHLIGHTS PORTIONS OF THE OHIO VALLEY, MIDWEST, AND CENTRAL HIGH
PLAINS. THE FRONTAL BOUNDARY WILL REMAIN SLOW MOVING INTO THE
WEEKEND REINFORCING MULTIPLE DAYS OF SHOWERS AND THUNDERSTORMS
ACROSS THE SAME AREAS, BUT BY SUNDAY THE FRONTAL BOUNDARY WILL LIFT
INTO THE GREAT LAKES AND MID- ATLANTIC AND PORTIONS OF THE
NORTHEAST, PUSHING THE SHOWERS AND THUNDERSTORMS FURTHER NORTHEAST
INTO THE UPPER MIDWEST, NORTHEAST, AND MID- ATLANTIC.
ACROSS THE SOUTHWEST, GREAT BASIN, ROCKIES, AND INTERIOR
CALIFORNIA, A UPPER LEVEL TROUGH WILL MOVE INTO THE WEST BY LATE
WEEK, SUPPORTING LOW-LEVEL FLOW OF MONSOONAL MOISTURE, WHICH WILL
LEAD TO THE DEVELOPMENT OF SCATTERED TO NUMEROUS THUNDERSTORMS.
SOME STORMS WILL PRODUCE HEAVY RAINFALL OVER SHORT PERIODS,
DESPITE RELATIVELY MODEST STORM MOTIONS. REPEATED CONVECTION MAY
LEAD TO FLASH FLOODING IN VULNERABLE TERRAIN, INCLUDING BURN SCARS,
SLOT CANYON, AND URBANIZED AREAS. THEREFORE, A BROAD MARGINAL RISK
ON DAY 4 ERO HIGHLIGHTS MUCH OF THE AREA WITH A SLIGHT RISK OVER
PORTIONS OF THE ROCKIES/PLAINS AND PORTIONS OF THE FOUR CORNERS.
ACROSS THE SOUTHEAST, A PORTION OF THE FRONTAL BOUNDARY WILL DROP
SOUTHWARD INTO PORTIONS OF THE SOUTHEAST AND A SURFACE TROUGH WILL
DEVELOP AHEAD OF THE FRONT BY FRIDAY AND INTERACT WITH WARM MOIST
AIRMASS, WHICH WILL SUPPORT SCATTERED THUNDERSTORM DEVELOPMENT
THROUGH THE WEEKEND.
THE SOUTHERN PLAINS, GULF COAST AND SOUTHEAST WILL REMAIN UNDER
THE INFLUENCE OF THE PERSISTENT UPPER RIDGE. TEMPERATURES WILL
REMAIN WELL ABOVE NORMAL, WITH PORTIONS OF THE SOUTHERN PLAINS
REACHING THE LOWER 100S AND WIDESPREAD 90S EXTENDING EASTWARD
ACROSS THE SOUTHEAST. HIGH DEWPOINTS WILL KEEP HEAT INDICES
ELEVATED, RESULTING IN POTENTIALLY DANGEROUS HEAT CONDITIONS WHERE
THE HEAT PERSIST FOR SEVERAL CONSECUTIVE DAYS. MAJOR HEATRISK
CONDITIONS ARE EXPECTED ACROSS A BROAD PORTION OF THE REGION, WITH
LOCALLY EXTREME HEATRISK POSSIBLE.
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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