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FXUS21 KWNC 071858
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 07 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FAVORED TO PERSIST OVER THE SOUTHERN AND
SOUTHWESTERN CONTIGUOUS U.S. (CONUS) DURING WEEK-2, LEADING TO AN ELEVATED
POTENTIAL FOR EXCESSIVE HEAT FOR MUCH OF THE SOUTHWESTERN CONUS, EXTENDING INTO
THE SOUTHERN PLAINS AND OVER PARTS OF THE SOUTHEAST. THERE IS AN INCREASED
POTENTIAL FOR HEAVY PRECIPITATION EARLY IN THE PERIOD ACROSS PORTIONS OF THE
CENTRAL PLAINS AND EXTENDING EASTWARD INTO THE MIDDLE MISSISSIPPI, OHIO, AND
TENNESSEE VALLEYS, ALONG A MEAN FRONTAL BOUNDARY. FLOODING IS ALSO POSSIBLE
ALONG 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 FOUR CORNERS REGION AND WEST TEXAS,
SAT-TUE, JUL 15-18.
HIGH RISK OF EXCESSIVE HEAT FOR THE SOUTHERN FLORIDA PENINSULA, SAT-TUE, JUL
15-18.
MODERATE RISK OF EXCESSIVE HEAT FOR MOST OF THE SOUTHWESTERN CONUS AND PARTS OF
THE SOUTHERN PLAINS, SAT-THU, JUL 15-20.
MODERATE RISK OF EXCESSIVE HEAT FOR THE FLORIDA PENINSULA, SAT-THU, JUL 15-20
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHERN CONUS, SAT-FRI, JUL
15-21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR EASTERN PORTIONS OF THE CENTRAL AND
SOUTHERN PLAINS, EXTENDING INTO THE MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE
VALLEYS, SAT-SUN, JUL 15-16.
SLIGHT RISK OF PERIODS OF HIGH WINDS FOR PORTIONS OF THE SOUTHERN PLAINS AND
FOUR CORNERS, SAT-FRI, JUL 15-21.
FLOODING POSSIBLE FOR PORTIONS OF NORTHEASTERN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF EASTERN TEXAS AND CENTRAL LOUISIANA.
DETAILED SUMMARY
FOR MONDAY JULY 10 - FRIDAY JULY 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JULY 15 - FRIDAY JULY 21: 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. THERE IS MUCH BETTER AGREEMENT AMONG THE DYNAMICAL MODEL
GUIDANCE IN THE LOCATION OF THE MEAN MID-LEVEL RIDGE AXIS AND ITS EVOLUTION
DURING WEEK-2, COMPARED TO YESTERDAY. 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 MUCH OF NEW MEXICO,
ARIZONA, AND PARTS OF WEST TEXAS, WARRANTING A HIGH RISK OF EXCESSIVE HEAT FOR
THESE REGIONS JUL 15-18. THE GEFS, ECMWF, AND CMCE 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, EXTENDING ACROSS PARTS OF
THE FOUR CORNERS REGION JUL 15-20, WARRANTING A MODERATE RISK OF EXCESSIVE HEAT
FOR THE FOUR CORNERS AND MUCH OF THE SOUTHERN HIGH PLAINS. THE MODERATE RISK
ALSO EXTENDS INTO NEVADA AND PARTS OF CALIFORNIA, BUT IS FAVORED TO TIME OFF
FOR THOSE AREAS AROUND JUL 17, CORRESPONDING TO DIMINISHING HEAT SIGNALS IN
THOSE AREAS BEYOND THAT TIME. GEFS AND ECMWF PETS INDICATE AT LEAST A 20%
CHANCE OF HIGH TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND
105 DEG F THROUGH JUL 17 IN THE SAN JOAQUIN VALLEY. ADDITIONALLY, THE PETS
INDICATE AT LEAST A 20% PROBABILITY OF EXCEEDING THE 85TH PERCENTILE FOR MUCH
OF THE SOUTHERN AND SOUTHWESTERN CONUS FOR THE ENTIRE WEEK-2 PERIOD, THUS A
SLIGHT RISK FOR EXCESSIVE HEAT IS POSTED ACROSS MUCH OF THE SOUTHERN TIER FROM
THE PACIFIC TO ATLANTIC COASTS, EXTENDING NORTHWARD TO INCLUDE MUCH OF THE
CENTRAL INTERMOUNTAIN WEST. HOWEVER, IT SHOULD BE NOTED THAT THE MODELS ARE A
BIT CONFLICTED WITH RESPECT TO THE STRENGTH OF THE HEAT SIGNALS IN THE
SOUTHEAST, PARTICULARLY FROM THE CENTRAL GULF COAST TO THE ATLANTIC COASTAL
PLAIN. DESPITE SOME UNCERTAINTY AMONG FORECAST TOOLS ALONG THE CENTRAL GULF
COAST AND THE COASTAL PLAIN OF THE CAROLINAS AND VIRGINIA, THE TOOLS ARE IN
DECENT AGREEMENT WITH RESPECT TO ENHANCED HEAT SIGNALS ACROSS THE FLORIDA
PENINSULA. THE ECMWF PET INDICATES AT LEAST A 60% CHANCE OF MAXIMUM
TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE FROM JUL 15-18 ACROSS
THE SOUTHERN HALF OF THE FLORIDA PENINSULA, WARRANTING A HIGH RISK OF EXCESSIVE
HEAT. AN ENCOMPASSING MODERATE RISK OF EXCESSIVE HEAT IS ALSO POSTED, WHICH
COVERS THE ENTIRE FLORIDA PENINSULA, WHERE THE ECMWF PET INDICATES AT LEAST A
40% CHANCE OF DAYTIME TEMPERATURES EXCEEDING THE 85TH PERCENTILE. ALTHOUGH
SIGNALS ARE SLIGHTLY MUTED IN THE GEFS PET, SPATIAL AGREEMENT IS VERY GOOD. IN
ADDITION, IT IS IMPORTANT TO NOTE THAT THE HEAT RISKS ACROSS THE FLORIDA
PENINSULA ARE PREDOMINANTLY DUE TO FORECAST HEAT INDICES, WHICH COULD EXCEED
105 DEG F. HOWEVER, POSITIVE MAXIMUM TEMPERATURE ANOMALIES FORECAST FOR THE
PERIOD ARE FAVORED TO ONLY BE UPWARDS OF 3 TO 5 DEG F FOR THE WEEK-2 PERIOD AS
A WHOLE.
AT THE BEGINNING OF WEEK-2 MULTIPLE MODEL SOLUTIONS CONTINUE TO DEPICT
MID-LEVEL TROUGHING OVER THE GREAT LAKES. A MEAN FRONTAL BOUNDARY IS FORECAST
BETWEEN THIS TROUGH AND THE MID-LEVEL RIDGE OVER THE SOUTHWESTERN AND SOUTHERN
CONUS. ALONG THIS MEAN FRONTAL BOUNDARY, THERE IS AN INCREASED POTENTIAL FOR
HEAVY PRECIPITATION, WHICH COULD BE IN THE FORM OF CLUSTERS OF THUNDERSTORMS
(KNOWN AS MESOSCALE CONVECTIVE SYSTEMS, OR MCSS). THEREFORE, A SLIGHT RISK OF
HEAVY PRECIPITATION IS POSTED ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
EXTENDING INTO THE MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS FOR JUL
15-16. THE PETS SUPPORT THIS POTENTIAL, WITH THE ECMWF AND CMCE BOTH INDICATING
AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85
CLIMATOLOGICAL PERCENTILE AND 1 INCH, WHICH WOULD MOSTLY OCCUR DURING THE FIRST
2 DAYS OF WEEK-2, JUL 15-16. THE TROUGHING OVER THE GREAT LAKES IS FORECAST TO
DEAMPLIFY TOWARD THE MIDDLE AND LATTER PORTIONS OF WEEK-2, WHICH WILL ACT TO
DIMINISH THE THREAT OF HEAVY PRECIPITATION IN THE CENTRAL AND EASTERN CONUS.
A SLIGHT RISK OF PERIODS OF HIGH WINDS IS POSTED FOR PARTS OF THE SOUTHERN
PLAINS AND FOUR CORNERS REGION, WHERE GEFS AND ECMWF PETS INDICATE AT LEAST A
20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE OF THE HISTORICAL
DISTRIBUTION FOR THE ENTIRE WEEK-2 PERIOD. FIRE RISK REMAINS MODERATE TO VERY
HIGH ACROSS LARGE PORTIONS OF THE SOUTHWESTERN CONUS, WITH THE RISK OF HIGH
WINDS AND EXCESSIVE HEAT ACTING ONLY TO EXACERBATE THAT RISK.
THE RISK OF DROUGHT DEVELOPMENT IS FORECAST TO INCREASE ACROSS PARTS OF EAST
TEXAS AND PARTS OF LOUISIANA, DUE TO RECENT (IN SOME CASES RECORD) HEAT IN
RECENT WEEKS THAT IS FORECAST TO PERSIST THROUGH MUCH OF THE WEEK-2 PERIOD. IN
ADDITION, INCREASED CHANCES OF BELOW-NORMAL PRECIPITATION IS FORECAST FOR THESE
SAME AREAS. AS SUCH, A RISK OF RAPID ONSET DROUGHT (ROD) IS POSTED 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 AND 80 DEG F ACROSS THESE SAME AREAS DURING WEEK-2.
THE ONGOING DRYNESS, COUPLED WITH THE POTENTIAL FOR ABOVE-NORMAL TEMPERATURES,
WILL ACT TO ELEVATE FIRE CONCERNS FOR SEVERAL OF THESE LOCATIONS.
FORECASTER: ADAM HARTMAN
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