244
FXUS02 KWBC 110659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT TUE AUG 11 2026
VALID 12Z FRI AUG 14 2026 - 12Z TUE AUG 18 2026
..SOUTH-CENTRAL TO SOUTHEAST U.S. HAZARDOUS HEAT THREAT
..SOUTHWEST/GREATASIN/ROCKIES MONSOONAL HEAVY RAIN THREAT
..NORTH-CENTRAL U.S. TO MIDWEST/MID-ATLANTIC HEAVY RAIN THREAT
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE FORECAST SPREAD IS TRENDING FAVORABLY LOWER OVER
MEDIUM-RANGE TIME SCALES. DESPITE LINGERING SYSTEM TIMING AND FOCUS
DIFFERENCES, OVERALL FORECAST CONFIDENCE HAS BROADLY IMPROVED WITH
RESPECT TO FLOW EVOLUTION AND INHERENT THREAT MESSAGING GIVEN THE
REASONABLY WELL DEFINED AND PERSISTENT SUMMER PATTERN. A FAVORED
COMPOSITE OF COMPATIBLE MODELS AND ENSEMBLES TENDS TO MITIGATE
SYSTEM VARIANCES CONSISTENT WITH INDIVIDUAL PREDICTABILITY TO
PROVIDE A SOLID FORECAST BASIS OVERALL CONSISTENT WITH THE NATIONAL
BLEND OF MODELS AND ACTS TO MAINTAIN GOOD WPC PRODUCT CONTINUITY.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
A PROTRACTED HEATWAVE WILL BROADLY LINGER FROM THE SOUTH-CENTRAL
TO SOUTHEAST U.S. UNDER THE INFLUENCE OF A PERSISTENT UPPER RIDGE.
TEMPERATURES WILL REMAIN WELL ABOVE NORMAL AS PORTIONS OF THE
SOUTHERN PLAINS REACH THE LOWER 100S, WHILE WIDESPREAD 90S EXTEND
EASTWARD ACROSS THE SOUTHEAST. HIGH DEW POINTS/HUMIDITY WILL KEEP
HEAT INDICES ELEVATED, RESULTING IN DANGEROUS HEAT CONDITIONS.
WIDESPREAD RECORD OVERNIGHT TEMPERATURES WILL PROVIDE LITTLE
RELIEF. MAJOR HEATRISK CONDITIONS ARE EXPECTED ACROSS A BROAD
PORTION OF THE REGION, WITH LOCALLY EXTREME HEATRISK POSSIBLE.
MEANWHILE, MONSOONAL MOISTURE AND FLOW EMBEDDED VORTS WILL CHANNEL
OVER THE SOUTHWEST/GREAT BASIN AND ROCKIES BETWEEN AN EASTERN
PACIFIC UPPER TROUGH AND THE WESTERN PERIPHERY OF THE SOUTHERN U.S.
UPPER RIDGE THIS PERIOD. THIS WILL LEAD TO THE DEVELOPMENT OF
SCATTERED TO NUMEROUS THUNDERSTORMS, PARTICULARLY OVER THE SOUTH-
CENTRAL ROCKIES STATES WHERE A WPC DAY4/FRIDAY EXCESSIVE RAINFALL
OUTLOOK (ERO) SLIGHT RISK AREA HAS BEEN INTRODUCED. THE DAY
4/FRIDAY AND DAY 5/SATURDAY EROS ALSO SHOW A BROAD SURROUNDING
MARGINAL RISK AREAS. SOME STORMS WILL PRODUCE EXCESSIVE RAINFALL
OVER SHORT PERIODS WHILE MOVING RATHER SLOWLY. REPEATED CONVECTION
MAY LEAD TO FLASH FLOODING IN VULNERABLE TERRAIN, INCLUDING BURN
SCARS, SLOT CANYONS, AND URBANIZED AREAS.
ELSEWHERE, PROGRESSIVE FLOW WILL PERSIST ACROSS THE U.S NORTHERN
TIER OF THE CENTRAL TO EASTERN U.S. OVERTOP THE POTENT SOUTHERN
U.S. UPPER RIDGE. MULTIPLE SHORTWAVES WILL CROSS THE REGION
THROUGH THE PERIOD AND INTERACT WITH A SLOW-MOVING AND WAVY FRONTAL
ZONE EXTENDING FROM THE NORTHERN/CENTRAL ROCKIES INTO THE CENTRAL
PLAINS, MIDWEST, OHIO/TENNESSEE VALLEYS AND INTO THE EAST. RICH
LOW-LEVEL MOISTURE, INSTABILITY, AND FORCING WILL SUPPORT PERIODIC
CLUSTERS OF SHOWERS AND STRONG THUNDERSTORMS WITH LOCALLY HEAVY
RAINFALL POTENTIAL AND FLOODING CONCERNS. THE DAY 4/FRIDAY ERO
HAS INTRODUCED A SLIGHT RISK THREAT AREA CENTERED OVER THE CORN
BELT GIVEN REPEAT CONVECTION POTENTIAL. THE DAY 4/FRIDAY AND DAY
5/SATURDAY EROS ALSO SHOW BROAD SURROUNDING MARGINAL RISK AREAS.
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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