837
FXUS02 KWBC 121802
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 PM EDT TUE AUG 12 2025
VALID 12Z FRI AUG 15 2025 - 12Z TUE AUG 19 2025
..OVERVIEW
DURING THIS PERIOD TROUGHING WILL BE PRESENT OVER THE WEST WITH
RIDGING OVER THE EAST INITIALLY BEFORE SLOW RETROGRESSION WESTWARD
OF THE ENTIRE PATTERN INTO EARLY NEXT WEEK. AS THIS PATTERN IS IN
TRANSITION, THE RIDGE IS EXPECTED TO BUILD INTO THE SOUTHERN
PLAINS/ROCKIES WITH TROUGHING DIPPING INTO THE NORTHEAST. THERE
WILL BE A STARK TEMPERATURE CONTRAST WITH COOL IN THE WEST AND
WARM/HOT IN THE EAST THAT WILL MODERATE AS THE NEW WEEK PROGRESSES.
WITH THE RIDGE AXIS SHIFTING WESTWARD SO WILL THE WARMING
TEMPERATURES. RAINFALL WILL FOCUS OVER THE NORTHERN TIER (UPPER
MIDWEST/GREAT LAKES) IN ASSOCIATION WITH THE STORM TRACK, ACROSS
THE SOUTHEAST, AND OVER THE SOUTHWEST. IN ADDITION, A MODESTLY
STRONG COLD FRONT WILL BRING APPRECIABLE RAIN TO THE PACIFIC
NORTHWEST ON FRIDAY/SATURDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST SUITE OF GUIDANCE REMAINS FAIRLY CLUSTERED THROUGH THE
EXTENDED PERIOD WITH THE BROAD UPPER RIDGE AND BOOKEND TROUGHS NEAR
EACH COAST. THERE CONTINUES TO BE TIMING DIFFERENCES WITH
INDIVIDUAL EMBEDDED SHORTWAVE BUT NOTHING EGREGIOUS FOR THIS TIME
PERIOD. THE NATIONAL HURRICANE CENTER IS TRACKING TROPICAL STORM
ERIN, WHICH MAY START TO GET CLOSE TO THE SOUTHEASTERN BOUNDARY OF
THE DOMAIN BY NEXT TUESDAY PER THE LATEST FORECAST. PLEASE SEE THE
NHC WEBSITE FOR THE MOST UP-TO-DATE INFORMATION.
..WEATHER/HAZARDS HIGHLIGHTS
OVER THE WEEKEND THERE ARE THREE REGIONS WHERE THERE MAY BE
EXCESSIVE RAINFALL AND ISOLATED AREAS OF FLASH FLOODING -- THE
UPPER MIDWEST, SOUTHERN APPALACHIANS/SOUTHEAST, AND THE SOUTHWEST.
SHOWERS AND THUNDERSTORMS WILL LIKELY FIRE UP ALONG AND AHEAD OF
AN APPROACHING COLD FRONT. PERSISTENT HIGH MOISTURE LEVELS OVER
THE SOUTHEAST, WHEN COMBINED WITH AFTERNOON HEATING, WILL TRIGGER
SHOWERS AND STORMS DEVELOPMENT DURING THE AFTERNOON. THE LAST AREA
(SOUTHWEST) WILL SEE AN INCREASE IN MOISTURE INTO THE REGION.
THOUGH AMOUNTS MAY BE LIGHT OVERALL, SOME STORMS WILL STILL BE
CAPABLE OF PRODUCING HEAVIER RAINFALL THAT MAY FALL OVER MORE
SENSITIVE AREAS (STEEP TERRAIN, IN/AROUND BURN SCARS, ETC.). FOR
THE REST OF THE PERIOD, RAINFALL MAY EASE A BIT IN THE SOUTHWEST
REMAIN WIDESPREAD ACROSS THE UPPER MIDWEST/GREAT LAKES AS THE
FRONTAL BOUNDARY STALLS ACROSS THE REGION.
VERY WARM TEMPERATURES WILL PERSIST OVER MUCH OF THE CENTRAL AND
EASTERN U.S. THIS WEEKEND, WITH MANY AREAS CLIMBING INTO THE 90S
WITH HEAT INDICES AROUND 100F. 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 INTO THE MID-
ATLANTIC. HIGH TEMPERATURES AND HUMIDITY WILL COMBINE TO MAKE FOR
VERY UNCOMFORTABLE CONDITIONS AS WELL OVER FLORIDA LATE THIS WEEK
AND ALONG THE GULF COAST INTO THE WEEKEND. WITH THE COLD FRONT
APPROACHING FROM THE NORTH, COOLER AIR FILTERING IN WILL PROVIDE
SOME DEGREE OF RELIEF FROM THE GREAT LAKES TO THE NORTHEAST. FOR
THE WEST COAST, THE WEEKEND WILL BE MUCH COOLER THAN SEASONAL
AVERAGE FOR AUGUST HOWEVER TEMPERATURES ARE EXPECTED TO SLOWLY
REBOUND AS THE TROUGHING EASES BACK WESTWARD. COASTAL AREAS MAY
ONLY SEE HIGHS INTO THE 60S AND LOW 70S WITH INLAND AREAS ONLY IN
THE 80S TO LOW 90S. EVEN THE SOUTHWEST WILL LIKELY SEE TEMPERATURES
A BIT COOLER THAN NORMAL -- 90S TO LOW 100S FOR THE DESERT CITIES
INSTEAD OF 100-110F+. HOWEVER, THE HEAT MAY START TO RETURN OVER
THE FOUR CORNERS REGION BY TUESDAY AS THE UPPER RIDGE MOVES INTO
THE AREA FROM THE EAST.
CAMPBELL/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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