291
FXUS02 KWBC 011856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI AUG 1 2025
VALID 12Z MON AUG 04 2025 - 12Z FRI AUG 08 2025
...MAJOR TO EXTREME HEAT THREATS INCREASING ACROSS PARTS THE
SOUTHWEST LATER NEXT WEEK...
..OVERVIEW
A COOLING UPPER TROUGH SET TO SETTLE INTO THE EASTERN THIRD OF THE
NATION WILL BE REINFORCED INTO NEXT WEEK BY DISTURBANCES DROPPING
SOUTHEAST ACROSS THE PLAINS. THIS IS 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 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. MEANWHILE, UPPER TROUGHING IS FORECAST TO PUSH
THROUGH THE NORTHWEST WITH FRONTS FORECAST TO MOVE INTO THE
NORTHERN ROCKIES/PLAINS TO FIRE LOCAL THUNDERSTORMS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE GENERALLY SHOWS GOOD AGREEMENT ON THE OVERALL LARGE
SCALE PATTERN EVOLUTION DURING THE MEDIUM RANGE PERIOD, BUT
UNCERTAINTY IN THE DETAILS AND TIMING OF SYSTEMS, ESPECIALLY ACROSS
THE NORTHWEST. EVEN EARLY IN THE PERIOD, THE UKMET GETS SOMEWHAT
OUT OF PHASE/SLOWER AND WAS NOT USED IN THE WPC FORECAST BLEND AT
ALL. BY WEDNESDAY AND AFTER, THE CMC WAS A BIT MORE AMPLIFIED INTO
THE NORTHERN PLAINS WITH ANOTHER SHORTWAVE. OTHERWISE, VERY GOOD
AGREEMENT WITH THE BUILDING RIDGE ACROSS THE SOUTHWEST NEXT WEEK.
THE WPC FORECAST WAS BASED ON A BLEND OF THE DETERMINISTIC (MINUS
THE UKMET) GUIDANCE FOR MONDAY AND TUESDAY, THEN INCREASING TO
ROUGHLY HALF GFS/ECMWF WITH ENSEMBLE MEANS. THIS MAINTAINS GOOD
AGREEMENT WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
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 ARE IN PLAY DAY 4/MONDAY AND DAY 5/TUESDAY FOR
THE SOUTHEAST INTO SOUTHERN PORTIONS OF THE MID-ATLANTIC.
FARTHER WEST, SHORTWAVES ROUNDING INTO THE EASTERN EDGE OF THE
UPPER RIDGE FROM THE ROCKIES/HIGH PLAINS ARE FORECAST TO INTERACT
WITH A DOWNSTREAM FRONTAL ZONE. BY EARLY NEXT WEEK, THERE IS A SOME
TREND FOR THE OHIO/TENNESSEE VALLEYS TO SEE INCREASING RAIN AND
STORMS. RAIN AND STORMS ARE GENERALLY FORECAST TO OVERSPREAD THE
EAST-CENTRAL U.S. TUESDAY AND THE EAST MID-LATER NEXT WEEK.
ELSEWHERE, LINGERING RAIN AND CONVECTION IS POSSIBLE OVER THE
INTERIOR NORTHWEST INTO MONDAY COINCIDENT WITH THE UPPER TROUGH.
LEAD MOISTURE AND INSTABILITY WILL BE ABOVE NORMAL FOR THE NORTHERN
ROCKIES/PLAINS. A MARGINAL RISK IS DEPICTED IN THE DAY 4/MONDAY
ERO FOR NORTHWESTERN MONTANA AS THE SHORTWAVE MOVES THROUGH AND
PROVIDES LIFT WITH A SECONDARY MARGINAL DOWNSTREAM ACROSS PARTS OF
THE DAKOTAS AND MINNESOTA. RAIN AND THUNDERSTORMS ARE EXPECTED TO
ALSO CONTINUE FROM SOUTHERN CENTRAL CANADA DOWN INTO THE NORTHERN
PLAINS TUESDAY WITH ANOTHER DAY 5 MARGINAL RISK ERO AREA, WITH
ACTIVITY LIKELY TO SPREAD OVER THE UPPER MIDWEST MID- 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.
COOLER THAN AVERAGE TEMPERATURES ARE LIKELY ON THE COOL SIDE OF
THE MAIN FRONTAL SYSTEM EARLY NEXT WEEK. THE SOUTHEAST AND MUCH OF
THE CENTRAL U.S. CAN EXPECT HIGHS OF 5-10 DEGREES BELOW AVERAGE,
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 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.
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 BY NEXT WEDNESDAY.
FLORIDA IS FORECAST TO SEE SEASONABLE TEMPERATURES IN THE 90S, BUT
WITH AMPLE HUMIDITY ALLOWING FOR SOME AREAS OF MAJOR HEATRISK THERE
AS WELL.
SANTORELLI/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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