219
FXUS02 KWBC 070627
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
227 AM EDT FRI AUG 7 2026
VALID 12Z MON AUG 10 2026 - 12Z FRI AUG 14 2026
...HEAT WAVE WANES IN SOUTHWEST EARLY NEXT WEEK, WHILE HEAT
THREAT EXPANDS ACROSS THE CENTRAL AND SOUTHEASTERN U.S....
...MULTI-DAY HEAVY RAINFALL POTENTIAL FOR OHIO VALLEY AND CENTRAL
APPALACHIANS EARLY NEXT WEEK...
..OVERVIEW
TWO DISTINCT TROUGHS, ONE OVER THE NORTHEAST PACIFIC AND ANOTHER
OVER HUDSON BAY WILL PROMOTE STORMY CONDITIONS FROM THE CENTRAL TO
EASTERN U.S. NEXT WEEK. MEANWHILE, AN UPPER RIDGE CENTERED OVER
THE SOUTHWEST WILL WEAKEN AS IT SHIFTS EAST INTO THE
SOUTHERN/CENTRAL PLAINS AND DEEP SOUTH WHERE ANOTHER HEAT WAVE MAY
DEVELOP.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE APPEAR TO BE IN
REASONABLY GOOD AGREEMENT REGARDING THE OVERALL SYNOPTIC EVOLUTION
OF THE 500 MB PATTERN DURING THE MEDIUM RANGE PERIOD. THE ECAIFS
IS THE ONLY OUTLIER, PARTICULARLY EARLY IN THE PERIOD, WITH IT
NOTABLY AMPLIFYING A WEST COAST TROUGH AND DISPLAYING A WEAKER
RIDGE IN THE SOUTHWEST COMPARED TO THE OTHER MODELS.
A GENERAL MODEL BLEND CONSISTING OF THE AVAILABLE DETERMINISTIC
GUIDANCE WAS USED IN THE DAYS 3 AND 4 BLENDS WITH GREATER WEIGHTING
GIVEN TO THE GFS AND EURO. THE GEFS AND ECENS WERE INTRODUCED TO
THE BLEND BEGINNING ON DAY 5 AND INCREASED IN WEIGHTING THROUGH THE
END OF THE PERIOD, TO MITIGATE GROWING DIFFERENCES IN THE
EVOLUTION OF THE EAST COAST TROUGH. THE CMCE WAS INTRODUCED TO THE
BLEND ON DAY 6 AND CONTINUED THROUGH THE END OF THE PERIOD AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
A LONG SURFACE FRONT DRAPED ACROSS THE NORTHERN TIER ON MONDAY WILL
SLOWLY DRIFT SOUTH OVER THE NEXT FEW DAYS. THUNDERSTORMS AND HEAVY
RAINFALL WILL FOCUS AROUND THIS BOUNDARY, WITH SOME POTENTIAL FOR A
MULTI-DAY HEAVY RAINFALL EVENT UNFOLDING OVER PARTS OF THE OHIO
VALLEY AND CENTRAL APPALACHIANS BETWEEN MONDAY AND WEDNESDAY.
TO THE SOUTH, A RIDGE IN THE SOUTHWEST WILL DEGRADE AND SHIFT
EASTWARD BEGINNING EARLY NEXT WEEK. THIS WILL LEAD TO RENEWED
MOIST, SOUTHERLY FLOW INTO THE SOUTHERN PLAINS, GULF COAST AND
SOUTHEAST, WHERE HEAT INDICES COULD REACH 105 TO 115 DEGREES IN
SOME PLACES FOR MULTIPLE DAYS. OVERNIGHT TEMPERATURES IN THE 70S
WILL OFFER LITTLE TO NO RELIEF FOR THOSE WITHOUT ADEQUATE COOLING
AND/OR HYDRATION. TEMPERATURES BEGIN TO COOL ACROSS THE NORTHERN
PLAINS UPPER MIDWEST AND GREAT LAKES NEXT WEEK AS THE SURFACE
FRONT DESCENDS INTO THE MIDWEST AND EAST COAST.
A RETREATING RIDGE TO THE EAST SHOULD REINVIGORATE MOIST SOUTHERLY
FLOW INTO THE SOUTHWEST, WHICH WILL LIKELY PROMOTE INCREASED
MONSOONAL ACTIVITY NEXT WEEK. ISOLATED INSTANCES OF FLASH FLOODING
WILL BE POSSIBLE, ESPECIALLY OVER VULNERABLE SURFACES SUCH AS SLOT
CANYONS AND DRY WASHES.
KEBEDE
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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