745
FXUS21 KWNC 261812
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 26 2023
SYNOPSIS: A HEAT WAVE IS EXPECTED TO CONTINUE ACROSS THE LOWER MISSISSIPPI
VALLEY AND SOUTHEAST THROUGH EARLY WEEK-2 BEFORE TEMPERATURES MODERATE. A
MID-LEVEL RIDGE IS FORECAST TO STRENGTHEN OVER THE WEST DURING THE FIRST WEEK
OF AUGUST, LEADING TO AN INCREASING CHANCE OF EXCESSIVE HEAT FOR THIS REGION.
ANTECEDENT DRYNESS, LITTLE TO NO RAINFALL DURING THE NEXT WEEK, AND THE
LIKELIHOOD OF ABOVE-NORMAL TEMPERATURES THROUGH AT LEAST EARLY AUGUST SUPPORTS
A RAPID ONSET DROUGHT RISK ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY, GREAT
PLAINS, AND PACIFIC NORTHWEST.
HAZARDS
HIGH RISK OF EXCESSIVE HEAT FOR PARTS OF THE SOUTHEAST, LOWER MISSISSIPPI
VALLEY, AND EASTERN TEXAS, THU, AUG 3.
MODERATE RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHEAST, LOWER MISSISSIPPI
VALLEY, AND SOUTHERN GREAT PLAINS, THU-SAT, AUG 3-5.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHERN AND WESTERN
U.S.,THU-WED, AUG 3-9.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE EAST COAST, THU-MON, AUG 3-7.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF SOUTHERN TEXAS AND INTO LOUISIANA,
INTERIOR PORTIONS OF THE PACIFIC NORTHWEST, AND NORTHWESTERN NORTH DAKOTA.
DETAILED SUMMARY
FOR SATURDAY JULY 29 - WEDNESDAY AUGUST 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY AUGUST 03 - WEDNESDAY AUGUST 09: GFS, ECMWF, AND CANADIAN ENSEMBLE
MEAN SOLUTIONS DEPICT A BROAD ANOMALOUS 500-HPA RIDGE WITH HEIGHTS EXCEEDING
594-DM FROM THE SOUTHERN GREAT PLAINS EASTWARD ACROSS THE LOWER MISSISSIPPI
VALLEY AND GULF COAST STATES THROUGH AUGUST 5. THE EASTWARD EXTENT OF THIS
ANOMALOUS RIDGE WEAKENS LATER IN WEEK-2, AS RIDGING BECOMES MORE PRONOUNCED
UPSTREAM OVER THE WEST. BASED ON GOOD AGREEMENT OF THE EVOLVING 500-HPA HEIGHT
PATTERN ALONG WITH GUIDANCE FROM THE GEFS AND ECMWF PROBABILISTIC EXTREMES
TOOLS (PETS) AND AN UNCALIBRATED GEFS/ECMWF SKILL WEIGHTED HEAT INDEX FORECAST,
A HIGH RISK (60 PERCENT CHANCE) OF EXCESSIVE HEAT IS POSTED FOR EASTERN TEXAS,
THE LOWER MISSISSIPPI VALLEY, AND PARTS OF THE SOUTHEAST ON AUGUST 3. A
MODERATE RISK (40 PERCENT CHANCE) AREA IS SUPPORTED BY THE TOOLS AND COVERS A
MORE EXPANSIVE AREA OF THE SOUTH-CENTRAL AND SOUTHEASTERN CONUS THROUGH AUGUST
5. WITHIN THE HIGH AND MODERATE RISK AREAS FOR EXCESSIVE HEAT, DAILY MAXIMUM
HEAT INDEX (HI) VALUES ARE LIKELY TO EXCEED 105 DEGREES F WITH AN INCREASED
POTENTIAL OF HI VALUES TO REACH 110 DEGREES F. ALTHOUGH A SLIGHT RISK OF
EXCESSIVE HEAT IS VALID DURING THE ENTIRETY OF WEEK-2 FOR THE NEARLY THE ENTIRE
SOUTHERN CONUS, TOOLS DEPICT A MODERATION IN TEMPERATURES ACROSS THE LOWER
MISSISSIPPI VALLEY AND SOUTHEAST LATER IN WEEK-2.
DURING EARLY AUGUST, THE ENSEMBLE MEANS ARE IN GOOD AGREEMENT AND CONSISTENT
THAT 500-HPA HEIGHTS INCREASE THROUGHOUT THE WEST WITH THE PETS SUPPORTING A
BROAD SLIGHT RISK OF EXCESSIVE HEAT ACROSS THE SOUTHWEST, GREAT BASIN, AND
PARTS OF THE PACIFIC NORTHWEST. A MODERATE RISK OF EXCESSIVE HEAT MAY BE NEEDED
FOR THE SOUTHWEST IN SUBSEQUENT OUTLOOKS IF TOOLS/FORECAST CONFIDENCE INCREASES
THAT MAXIMUM TEMPERATURES REACH THE HAZARDS CRITERIA.
AN AMPLIFYING TROUGH RESULTS IN A SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH
OF THE EAST COAST WHERE THE ECMWF REFORECAST TOOL HAS AT LEAST A 20 PERCENT
CHANCE OF 3-DAY PRECIPITATION AMOUNTS EXCEEDING THE 85TH PERCENTILE AND ONE
INCH. ANY SLOW-MOVING THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL MAY CAUSE FLASH
FLOODING. THE VALID TIME FOR THIS PRECIPITATION HAZARD IS FROM AUGUST 3 TO 7,
BUT THE GREATEST CHANCE FOR HEAVY PRECIPITATION IS EXPECTED TO SHIFT SOUTHWARD
WITH TIME FROM THE NORTHEAST TO THE SOUTHERN MID-ATLANTIC AND COASTAL
SOUTHEAST.
AS OF 2PM EDT ON JULY 26, THE NATIONAL HURRICANE CENTER IS MONITORING A
TROPICAL WAVE SOUTH OF THE CABO VERDE ISLANDS AND STATE THAT IT HAS A 30
PERCENT CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT WEEK. THE GFS
MODEL REMAINS THE MOST BULLISH WITH STRENGTHENING THIS SYSTEM AS IT TRACKS
WEST-NORTHWESTWARD ACROSS THE TROPICAL ATLANTIC. BASED ON THE AMPLIFIED TROUGH
OVER THE WESTERN ATLATNIC, THIS POTENTIAL TC IS LIKELY TO RECURVE AWAY FROM THE
EAST COAST LATE NEXT WEEK, WHICH RECENT DETERMINISTIC GFS MODEL RUNS AND THEIR
ENSEMBLE MEMBERS DEPICT.
ALTHOUGH ANOMALOUS RIDGING AND ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR
ALASKA, MAXIMUM TEMPERATURES ARE LIKELY TO REMAIN BELOW HAZARDS THRESHOLDS.
FORECASTER: BRAD PUGH
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