497
FXUS21 KWNC 102003
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 10 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FAVORED TO PERSIST OVER THE SOUTHERN AND
WESTERN CONTIGUOUS U.S. (CONUS) CONTINUING ELEVATED POTENTIAL FOR EXCESSIVE
HEAT ACROSS THESE REGIONS, EXTENDING INTO THE MID-ATLANTIC, FROM WEEK-1 THROUGH
WEEK-2. POSSIBLE FLOODING IS ANTICIPATED TO CONTINUE FOR THE JAMES RIVER IN
NORTHEASTERN SOUTH DAKOTA, WHERE RIVER LEVELS ARE EXPECTED TO REMAIN HIGH
LEADING UP TO AND DURING WEEK-2. CONVERSELY, ABNORMALLY DRY CONDITIONS OVER
PORTIONS OF EASTERN TEXAS AND CENTRAL LOUISIANA INCREASES THE RISK OF RAPID
ONSET DROUGHT (ROD).
HAZARDS
HIGH RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHWESTERN CONUS, TUE-WED,
JUL 18-19.
MODERATE RISK OF EXCESSIVE HEAT FOR MOST OF THE SOUTHWESTERN CONUS AND PARTS OF
THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY, TUE-THU, JUL 18-20.
MODERATE RISK OF EXCESSIVE HEAT FOR CENTRAL AND SOUTHERN FLORIDA, TUE-THU, JUL
18-20.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE WESTERN AND SOUTHERN CONUS AND
MID-ATLANTIC, TUE-MON, JUL 18-24.
FLOODING POSSIBLE FOR PORTIONS OF NORTHEASTERN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF EASTERN TEXAS AND CENTRAL LOUISIANA.
DETAILED SUMMARY
FOR THURSDAY JULY 13 - MONDAY JULY 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JULY 18 - MONDAY JULY 24: ENSEMBLE MODEL SOLUTIONS FROM THE GEFS,
ECMWF, AND CMCE ALL DEPICT POSITIVE 500-HPA HEIGHT ANOMALIES CENTERED OVER THE
DESERT SOUTHWEST AND FOUR CORNERS IN EXCESS OF 595 DM PERSISTING THROUGHOUT THE
WEEK-2 PERIOD. ECMWF AND GEFS PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE AT
LEAST A 60% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE OF THE
HISTORICAL DISTRIBUTION ACROSS PARTS OF THE FOUR CORNERS, SOUTHERN NEVADA, AND
WEST TEXAS AT THE BEGINNING OF THE PERIOD, WARRANTING A HIGH RISK OF EXCESSIVE
HEAT FOR THESE REGIONS JUL 18-19. THE GEFS AND ECMWF PETS INDICATE AT LEAST A
40% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE
AND AT LEAST 100 DEG F FOR MUCH OF THE SOUTHERN PLAINS AND THE SOUTHWESTERN
CONUS JUL 18-20. THE GEFS AND ECWMF CALIBRATED HEAT TOOLS INDICATE GREATER THAN
A 40% CHANCE FOR HEAT INDEX VALUES EXCEEDING THE 90TH PERCENTILE ACROSS THESE
REGIONS, EXTENDING INTO PORTIONS OF THE LOWER MISSISSIPPI VALLEY WARRANTING A
MODERATE RISK OF EXCESSIVE HEAT ACROSS THE SOUTHWESTERN CONUS AND PARTS OF THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY, JUL 18-20. A MODERATE RISK IS
ALSO POSTED FOR CENTRAL AND SOUTHERN FLORIDA, JUL 18-20, WHERE THERE MAY BE
NEAR RECORD TEMPERATURES IN THE MID 90S (DEG F). A BROAD SLIGHT RISK OF
EXCESSIVE HEAT CONTINUES TO BE HIGHLIGHTED ACROSS THE WESTERN AND SOUTHERN
CONUS AND MID-ATLANTIC THROUGHOUT WEEK-2 BASED ON WHERE THE GEFS AND ECMWF PETS
INDICATE AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH
PERCENTILE. THE NATIONAL BLEND OF MODELS (NBM) SHOWS THE POTENTIAL FOR NEAR
RECORD BREAKING MAXIMUM TEMPERATURES EXCEEDING 105 DEG F ACROSS THE FOUR
CORNERS AT THE BEGINNING OF THE PERIOD. FURTHER EAST, THE NBM INDICATES THE
POTENTIAL FOR RECORD BREAKING MAXIMUM TEMPERATURES IN THE UPPER 90S (DEG F)
ACROSS SOUTHERN TEXAS, LOUISIANA, AND FLORIDA AT THE BEGINNING OF THE PERIOD
AND RECORD HIGH LOW TEMPERATURES IN THE 80S. RELATIVELY HIGH HUMIDITY IS
EXPECTED TO SUPPORT HIGH HEAT INDEX VALUES IN THESE REGIONS. ANTICIPATED HOT,
DRY CONDITIONS ACROSS THE SOUTHWESTERN CONUS AND SOUTHERN PLAINS MAY SUPPORT
ENHANCED WILDFIRE RISK, ESPECIALLY WHERE THE NATIONAL INTERAGENCY FIRE CENTER
(NIFC) SHOWS A MODERATE RISK OF SIGNIFICANT FIRE POTENTIAL AND HIGH RISK
TRIGGERS BY THE END OF WEEK-1.
THE RISK OF DROUGHT DEVELOPMENT IS CONTINUED FOR PARTS OF EAST TEXAS AND PARTS
OF LOUISIANA, DUE TO RECENT (IN SOME CASES RECORD) HEAT IN RECENT WEEKS AND
EXPECTED EXCESSIVE HEAT FORECAST TO PERSIST THROUGH MUCH OF THE WEEK-2 PERIOD.
IN ADDITION, INCREASED CHANCES OF BELOW-NORMAL PRECIPITATION IS FORECAST FOR
THESE SAME AREAS FOR WEEK-2. AS SUCH, A RISK OF RAPID ONSET DROUGHT (ROD) IS
MAINTAINED FOR MUCH OF EASTERN TEXAS AND CENTRAL LOUISIANA.
RECENT HEAVY RAINFALL HAS RESULTED IN A CONTINUATION OF ELEVATED STREAM FLOWS
ALONG THE JAMES RIVER IN NORTHEASTERN SOUTH DAKOTA, LEADING TO AN INCREASED
RISK OF FLOODING DURING WEEK-2 FOR SOME LOCATIONS ALONG THAT BASIN.
NO HAZARDS ARE POSTED FOR ALASKA. HOWEVER, PARTS OF THE YUKON FLATS CONTINUE TO
DRY OUT, WITH SOME LOCATIONS ALREADY FALLING INTO ABNORMAL DRYNESS AND MODERATE
DROUGHT (ACCORDING TO THE U.S. DROUGHT MONITOR). THE ECMWF AND CMCE PETS ALSO
INDICATE AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE ACROSS THESE SAME AREAS DURING WEEK-2. THE ONGOING
DRYNESS, COUPLED WITH THE POTENTIAL FOR ABOVE-NORMAL TEMPERATURES, IS
ANTICIPATED TO ELEVATE FIRE CONCERNS FOR PARTS OF THE STATE ESPECIALLY ACROSS
EASTERN PORTIONS WHERE THE NIFC INDICATES A MODERATE RISK OF SIGNIFICANT FIRE
POTENTIAL BY THE END OF WEEK-1.
FORECASTER: MELISSA OU
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