880
FXUS02 KWBC 021845
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 PM EDT SAT AUG 2 2025
VALID 12Z TUE AUG 05 2025 - 12Z SAT AUG 09 2025
...MAJOR TO EXTREME HEAT THREATS INCREASING ACROSS PARTS THE
SOUTHWEST LATER NEXT WEEK...
..OVERVIEW
A REFRESHING UPPER TROUGH SET TO SETTLE INTO THE EASTERN THIRD OF
THE NATION WILL BE PERIODICALLY REINFORCED NEXT WEEK BY
DISTURBANCES DROPPING SOUTHEAST ACROSS THE PLAINS AND MIDWEST. THIS
WILL BE TO THE LEE AND ON THE EASTERN EDGE OF AN UPPER RIDGE OVER
THE SOUTHWEST WHICH IS FORECAST TO BUILD AND EXPAND BY THE MIDDLE
OF NEXT WEEK LEADING TO AN INCREASE IN HEAT THREATS. A WAVY STALLED
FRONT WILL SUPPORT HEAVY RAIN THREATS MAINLY NEAR THE COASTAL
SECTIONS OF THE SOUTHEAST EARLY-MID NEXT WEEK, BUT AS A BERMUDA
HIGH BEGINS TO BUILD WESTWARD, WET WEATHER IS FORECAST TO SPREAD
GRADUALLY NORTHWARD UP THE EASTERN U.S. THROUGH MID-LATER NEXT
WEEK, ALBEIT WITH SOME UNCERTAINTY WITH EXPANSION TIMING.
MEANWHILE, UPPER TROUGHING IS FORECAST TO PUSH THROUGH AND EASTWARD
FROM THE NORTHWEST WITH LEADING FRONTS FORECAST TO WORK OVER THE
NORTHERN ROCKIES/PLAINS AND MIDWEST TO FIRE LOCAL THUNDERSTORMS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
UPDATED 00/06Z DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN GOOD
AGREEMENT ON THE OVERALL SYNOPTIC PATTERN THROUGH THE MEDIUM RANGE
PERIOD, WITH RUN-TO-RUN CONSISTENCY SUPPORTIVE OF ABOVE AVERAGE
PREDICTABILITY AS WELL. UPPER-LEVEL HIGHS ARE EXPECTED TO BUILD
OVER THE SOUTHWESTERN U.S. AND SOUTHWESTERN ATLANTIC, WITH THE MAIN
UPPER-FLOW PUSHED NORTHWARD TOWARDS THE U.S.-CANADIAN BORDER OVER
THE EASTERN/CENTRAL U.S. SHORTWAVES APPROACHING FROM THE
NORTHEASTERN PACIFIC WILL SUPPORT MEAN UPPER-TROUGHING OVER THE
WEST COAST/NORTHWESTERN U.S., AND ROUND THE NORTHERN SIDE OF THE
UPPER-HIGH. THIS PATTERN WILL KEEP PRECIPITATION CHANCES NEXT WEEK
GENERALLY LIMITED TO THE NORTH- CENTRAL U.S. AHEAD OF THE UPPER-
TROUGH, AND ACROSS PORTIONS OF THE SOUTHEASTERN U.S./GULF COAST
UNDER AN UPPER- LEVEL WEAKNESS BETWEEN THE HIGHS AND AS A LINGERING
FRONTAL BOUNDARY FROM THE PASSAGE OF THIS WEEK'S STRONG COLD FRONT
OVER THE EAST REMAINS. GUIDANCE DOES SHOW MORE UNCERTAINTY WITH
EXACT COVERAGE AND ESPECIALLY RANGE IN POTENTIAL RAIN AMOUNTS IN
BOTH REGIONS. FOR NOW, BROUGHT UP QPF VALUES A BIT COMPARED TO THE
NBM, BUT THERE REMAINS A HIGHER CEILING. BOTH THE DETERMINISTIC AND
MEAN GUIDANCE SUGGEST THE PATTERN WILL BEGIN TO CHANGE HEADING
INTO NEXT WEEKEND AS UPPER- LEVEL ENERGY OVER THE NORTHEASTERN
PACIFIC HELPS TO DIG THE UPPER- TROUGH SOUTHWARD, WITH THE UPPER-
HIGH OVER THE SOUTHWEST WEAKENING. THIS SHOULD LEAD TO INCREASINGLY
HEAVIER AND MORE WIDESPREAD PRECIPITATION CHANCES OVER THE
NORTHERN TIER WHILE THE HEATWAVE OVER THE SOUTHWEST TO
SOUTH/CENTRAL PLAINS MAY BEGIN TO ABATE. THE UPDATED WPC FORECAST
USED A COMPOSITE BLEND OF THE DETERMINISTIC GFS, ECMWF, CMC, AND
UKMET GUIDANCE GIVEN THE GOOD AGREEMENT, WITH A CONTRIBUTION FROM
THE GEFS/ECENS ADDED FOR THE LATTER PART OF THE PERIOD WITH THE
REMOVAL OF THE TIME-LIMITED UKMET.
..WEATHER/HAZARDS HIGHLIGHTS
IT GENERALLY REMAINS THE CASE THAT A RATHER EXPANSIVE COOL AIR
MASS WILL SETTLE INTO THE EASTERN U.S. FOR THE FIRST WEEK OF
AUGUST. HIGH MOISTURE CONTENT AND INSTABILITY NEAR A FRONT ON THE
LEADING EDGE OF THIS AIRMASS WILL FOCUS SOME LOCALIZED HEAVY RAIN
TO RAISE FLASH FLOODING RISKS GIVEN WET ANTECEDENT CONDITIONS. WPC
EXCESSIVE RAINFALL OUTLOOK (ERO) MARGINAL RISK AREAS HAVE BEEN
MAINTAINED FOR DAY 4/TUESDAY AND DAY 5/WEDNESDAY FOR THE SOUTHEAST
THROUGH SOUTH-CENTRAL PORTIONS OF THE APPALACHIANS/MID-ATLANTIC.
FARTHER WEST, SHORTWAVES ROUNDING INTO THE EASTERN EDGE OF THE
UPPER RIDGE FROM THE ROCKIES/PLAINS ARE FORECAST TO INTERACT WITH A
DOWNSTREAM FRONTAL ZONE. BY EARLY NEXT WEEK, THERE IS A TREND FOR
THE NORTHERN PLAINS/UPPER MIDWEST/GREAT LAKES TO SEE INCREASING
RAIN AND STORMS. WPC DAY 4/5 MARGINAL RISK ERO AREAS ARE DEPICTED
FOR TUESDAY AND WEDNESDAY GIVEN LIKELY MOISTURE/INSTABILITY POOLING
WITH SHORTWAVE PASSAGE. ACTIVITY WILL SPREAD MORE ACROSS THE GREAT
LAKES AND MIDWEST LATER NEXT WEEK. MEANWHILE, THE FOUR CORNERS
STATES COULD SEE SOME INCREASING MONSOON SHOWERS UNDERNEATH THE
BROAD RIDGE, AMID THE RELATIVELY DRY MONSOON SEASON ESPECIALLY
ACROSS UTAH/ARIZONA. SOME LIGHT TO MODERATE RAINFALL CHANCES CAN
ALSO BE EXPECTED THROUGH NEXT WEEK OVER THE PACIFIC NORTHWEST UNDER
THE INFLUENCE OF AN UPPER-LEVEL TROUGH.
COOLER THAN AVERAGE TEMPERATURES ARE LIKELY ON THE COOL SIDE OF
THE MAIN FRONTAL SYSTEM OVER THE CENTRAL TO EASTERN U.S. NEXT WEEK
AND SLOWLY MODERATE THROUGH THE PERIOD. THE SOUTHEAST AND MUCH OF
THE CENTRAL U.S. CAN EXPECT HIGHS OF 5-10 DEGREES BELOW AVERAGE
INTO EARLY NEXT WEEK, WITH LOCALLY GREATER ANOMALIES, AS HIGHS ONLY
REACH THE 70S AND LOW 80S FOR PARTS OF THE SOUTHEAST. THESE
TEMPERATURES SHOULD GRADUALLY WARM CLOSER TO NORMAL AS THE WEEK
PROGRESSES. THE NORTHWEST WILL ALSO GENERALLY BE COOLER THAN
AVERAGE UNDER ROUNDS OF UPPER TROUGHING. MEANWHILE ACROSS THE
SOUTHWEST, DANGEROUS HEAT WILL BUILD THROUGHOUT THE WEEK WITH SOME
LOCATION HIGH TEMPERATURES AS HIGH AS 110-115F, EQUATING TO MAJOR
TO EXTREME HEATRISK. SOME RELATIVE RELIEF MAY COME BY NEXT SATURDAY
AS THE UPPER-HIGH BEGINS TO WEAKEN. TEMPERATURES WILL ALSO BE
WARMING TO ABOVE NORMAL INTO THE SOUTHERN AND CENTRAL HIGH PLAINS
AS THE UPPER RIDGE EXPANDS. SOME RECORD HIGH TEMPERATURES THERE
COULD BE CHALLENGED AND ECLIPSED THROUGH MID- LATER NEXT WEEK.
FLORIDA IS FORECAST TO SEE SEASONABLE TEMPERATURES IN THE 90S, BUT
WITH AMPLE HUMIDITY ALLOWING FOR SOME AREAS OF MAJOR HEATRISK THERE
AS WELL.
PUTNAM/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 (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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