153
FXUS02 KWBC 140659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT THU AUG 14 2025
VALID 12Z SUN AUG 17 2025 - 12Z THU AUG 21 2025
..OVERVIEW
A TROUGH/RIDGE/TROUGH PATTERN SUNDAY WILL RETROGRADE WESTWARD
THROUGH THE WEEK, ALLOWING STRONG UPPER RIDGING TO ONCE AGAIN PUSH
BACK INTO THE FOUR CORNERS REGION. ACROSS THE NORTHERN TIER, THE
JET STREAM WILL MAINTAIN A FAIRLY ACTIVE WEATHER PATTERN THROUGH
THE START OF THE WEEK BEFORE IT SHIFTS A BIT FARTHER SOUTHEAST. THE
VERY WARM TEMPERATURES ACROSS THE CORN BELT TO THE MIDWEST WILL
SLIP BACK SEVERAL DEGREES THROUGH THE PERIOD, BUT REMAIN NEAR TO
JUST ABOVE NORMAL FOR MID-AUGUST. MUCH OF THE WEST WILL SEE WARMING
TEMPERATURES THROUGH THE WEEK. RAINFALL WILL FOCUS OVER THE
NORTHERN TIER (UPPER MIDWEST/GREAT LAKES) THEN INTO THE MIDWEST AND
NORTHEAST/MID-ATLANTIC TUE-THU, ACROSS FLORIDA, AND OVER THE
SOUTHWEST/SOUTHERN ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THROUGH THE 12Z/18Z GUIDANCE, A CONSENSUS BLEND APPROACH WORKED
WELL FOR A STARTING POINT TO THE FRONTS/PRESSURES AND SENSIBLE
WEATHER (VIA THE 01Z NBM). THE FLOW ACROSS CANADA AND THE NORTHERN
TIER OF THE CONUS REMAINS IN FLUX, MODULATED BY SHORTWAVES EJECTING
OUT OF THE WESTERN TROUGHING THAT MAY ACT TO FLATTEN THE FLOW EAST
OF 100W AND HELP MAINTAIN A MORE PROGRESSIVE TROUGH OVER EASTERN
CANADA (AS ADVERTISED BY THE ECMWF AIFS ENSEMBLES 24 HRS AGO). END
RESULT IS MUCH LESS TROUGHING INTO THE MIDWEST THAN PREVIOUSLY
ADVERTISED (PENDING FUTURE MODEL RUNS) AND, ESSENTIALLY, A BUCKLE
IN THE COLD FRONT THAT WILL EVENTUALLY PROGRESS SOUTHEASTWARD.
COMPLICATING THAT FURTHER IS THE LIKELY RECURVATURE OF TC ERIN
ALONG 70W. THAT MAY ACT TO HOLD UP THE FRONT OVER THE ATLANTIC BUT
PERHAPS ACCELERATE IT TO ITS WEST SIDE BY MIDWEEK NEXT WEEK ONCE IT
STARTS GAINING LATITUDE. PLEASE SEE THE NHC WEBSITE FOR THE MOST
UP-TO-DATE INFORMATION AS ERRORS IN POSITION 5+ DAYS CAN BE
SIGNIFICANT.
..WEATHER/HAZARDS HIGHLIGHTS
THERE WILL BE THREE MAIN REGIONS WHERE EXCESSIVE RAINFALL AND
ISOLATED AREAS OF FLASH FLOODING MAY DEVELOP SUN/MON -- THE UPPER
MIDWEST/NORTHERN HIGH PLAINS, SOUTHEAST/NORTHERN FLORIDA, AND THE
SOUTHWEST/SOUTHERN ROCKIES. A CONTINUED SURGE OF MOISTURE INTO THE
SOUTHWEST COMBINED WITH DIURNAL HEATING MAY TRIGGER STORMS CAPABLE
OF PRODUCING HEAVIER RAINFALL THAT MAY FALL OVER MORE SENSITIVE
AREAS (STEEP TERRAIN, IN/AROUND BURN SCARS, ETC.). OVER THE
NORTHERN REGION, A WAVY FRONTAL BOUNDARY WILL ACT AS A FOCUS FOR
SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL THAT MAY FALL
OVER AREAS THAT COULD SEE HEAVIER RAINFALL LEADING INTO THE MEDIUM
RANGE PERIOD. SINCE THE EXACT PLACEMENT OF THE HEAVIEST QPF
REMAINS A BIT UNCERTAIN, HELD OFF ON INDICATING A SLIGHT RISK IN
THE ERO. FOR THE SOUTHEAST, PERSISTENTLY HIGH MOISTURE LEVELS WHEN
COMBINED WITH AFTERNOON HEATING, WILL TRIGGER SHOWERS AND STORMS
DEVELOPMENT BOTH DAYS AS THE REMNANT MOISTURE OF AN OLD FRONT
CONTINUE TO SAG SOUTHWARD.
A VAST PORTION OF THE CENTRAL AND EASTERN U.S. WILL REMAIN ABOVE
NORMAL FOR DAILY MAXIMUM TEMPERATURES THIS UPCOMING WEEK, WITH WITH
MANY AREAS CLIMBING INTO THE 90S (HEAT INDICES AROUND 100F)
SUNDAY. THIS WILL DRIVE HEATRISK VALUES INTO THE THE MODERATE
(LEVEL 2) TO MAJOR (LEVEL 3 OUT OF 4) CATEGORY FROM THE CORN BELT
THROUGH THE MIDWEST (SUN/MON). HIGH TEMPERATURES/DEWPOINTS ACROSS
THE LOWER MISSISSIPPI VALLEY AND FLORIDA WILL KEEP CONDITIONS MUGGY
AND UNPLEASANT INTO NEXT WEEK. ACROSS THE WEST, COOLER THAN NORMAL
TEMPERATURES WILL MODERATE AS THE TROUGHING EASES BACK WESTWARD.
ABOVE NORMAL TEMPERATURES WILL LIKELY RETURN TO THE FOUR CORNERS
REGION BY TUESDAY AS THE UPPER RIDGE MOVES INTO THE AREA FROM THE
EAST. THIS MAY BRING MORE WIDESPREAD MODERATE HEATRISK VALUES TO
THE REGION WITH TEMPERATURES BACK TO AROUND 110F IN THE LOWER
DESERTS.
FRACASSO
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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