934
FXUS21 KWNC 211833
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 21 2023
SYNOPSIS: MID-LEVEL HIGH PRESSURE PERSISTS OVER THE SOUTHERN CONTIGUOUS U.S.
(CONUS) DURING WEEK-2, LEADING TO THE INCREASED POTENTIAL FOR EXCESSIVE HEAT
FOR THE SOUTHERN AND CENTRAL PLAINS. A MID-LEVEL CUT–OFF LOW OVER THE GREAT
LAKES COMBINED WITH ABUNDANT MOISTURE SUPPORTS AN ENHANCED RISK FOR HEAVY
PRECIPITATION TO PORTIONS OF THE NORTHEASTERN CONUS. SNOWMELT SEASON CONTINUES
FOR PORTIONS OF THE WEST AFTER EXCEPTIONAL WINTER ACCUMULATIONS, LEADING TO THE
CONTINUED POTENTIAL FOR FLOODING, WHILE ABNORMALLY DRY CONDITIONS OVER PORTIONS
OF WISCONSIN AND LOUISIANA RESULT IN THE POTENTIAL FOR RAPID ONSET DROUGHT
(ROD).
HAZARDS
HIGH RISK OF EXCESSIVE HEAT FOR PORTIONS OF EASTERN TEXAS, THU-FRI, JUN 29-30
MODERATE RISK FOR EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHERN AND CENTRAL
PLAINS AND LOWER AND MIDDLE MISSISSIPPI VALLEY, THU-SUN, JUN 29-JUL 2.
SLIGHT RISK FOR EXCESSIVE HEAT FOR THE CENTRAL AND SOUTHERN PLAINS, LOWER AND
MIDDLE MISSISSIPPI VALLEY, AND PORTIONS OF THE OHIO AND TENNESSEE VALLEYS,
SOUTHEASTERN U.S., SOUTHERN ROCKIES AND DESERT SOUTHWEST, THU-WED, JUN 29-JUL 5.
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE MID-ATLANTIC AND
NORTHEASTERN U.S., THU-MON, JUN 29-JUL 3.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA, NEVADA, UTAH, WYOMING, AND IDAHO.
POSSIBLE FLOODING ALONG PORTIONS OF THE JAMES RIVER IN SOUTH DAKOTA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF NORTHERN WISCONSIN AND CENTRAL
LOUISIANA.
DETAILED SUMMARY
FOR SATURDAY JUNE 24 - WEDNESDAY JUNE 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JUNE 29 - WEDNESDAY JULY 05: ENSEMBLE MODEL SOLUTIONS FROM THE
GEFS, ECMWF, AND CMCE ALL DEPICT POSITIVE 500-HPA HEIGHT ANOMALIES PERSISTING
OVER THE SOUTHERN CONUS THROUGHOUT THE FORECAST PERIOD WITH 500-HPA HEIGHTS
NEARING 600DM. THIS FAVORS ANOMALOUSLY WARM TEMPERATURES ACROSS THE SOUTHERN
AND CENTRAL CONUS, LEADING TO THE POTENTIAL FOR EXCESSIVE HEAT. THE GEFS AND
ECMWF PROBABILISTIC EXTREMES TOOLS (PET) INDICATE A BROAD AREA OF GREATER THAN
60% CHANCES OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE IN PARTS OF EASTERN TEXAS. THE NATIONAL BLEND OF MODELS (NBM)
INDICATES AN AREA OF POTENTIAL RECORD BREAKING HEAT IN THIS PART OF TEXAS AND
INTO LOUISIANA EARLY IN THE WEEK-2 PERIOD. THEREFORE, A HIGH RISK OF EXCESSIVE
HEAT IS POSTED FOR JUN 29-30 FOR PARTS OF EASTERN TEXAS. THE GEFS, ECMWF, AND
CMCE PET ALSO INDICATE AT LEAST A 40% PROBABILITY OF MAXIMUM TEMPERATURES
EXCEEDING THE 85TH PERCENTILE AND AT LEAST 95 DEGF FOR MUCH OF THE SOUTHERN AND
CENTRAL PLAINS, ALONG WITH PARTS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY,
WITH HIGH TEMPERATURES OVER 100 DEGF FOR MUCH OF TEXAS AND OKLAHOMA. IN THE
CENTRAL PLAINS AND MIDDLE MISSISSIPPI VALLEY THE CHANCES OF TEMPERATURES
REACHING THE 85TH PERCENTILE ARE GREATEST EARLY IN THE PERIOD BEFORE WEAKENING.
THIS MAY BE DUE TO INCREASED PRECIPITATION CHANCES DURING THE MIDDLE OF THE
WEEK-2 PERIOD. NEVERTHELESS, THE RISK IN MUCH OF THESE AREAS EXTENDS FROM JUN
29-JUL 2 FOR THE SOUTHERN AND CENTRAL PLAINS AS FAR NORTH AS THE
OKLAHOMA-KANSAS BORDER. THEREFORE A MODERATE RISK FOR EXCESSIVE HEAT IS
MAINTAINED DURING THIS PERIOD FOR PARTS OF THE SOUTHERN AND CENTRAL PLAINS AND
LOWER AND MIDDLE-MISSISSIPPI VALLEY. ADDITIONALLY, THERE IS MULTI-MODEL
DEPICTION IN THE PET INDICATING A BROAD AREA OF AT LEAST A 20% CHANCE OF
EXCEEDING THE 85TH PERCENTILE FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS,
LOWER AND MIDDLE MISSISSIPPI VALLEY, SOUTHEASTERN U.S., SOUTHERN ROCKIES, AND
DESERT SOUTHWEST, SUPPORTING A SLIGHT RISK OF EXCESSIVE HEAT FOR THESE REGIONS,
JUN 29-JUL 5. TWO AREAS OF PARTICULAR TO NOTE ARE IN THE CENTRAL PLAINS WHERE
THE PET INDICATE INCREASING CHANCES FOR TEMPERATURES TO EXCEED THE 85TH
PERCENTILE BUILDING BACK INTO THE CENTRAL PLAINS BY THE END OF THE FORECAST
PERIOD AND THERE IS A GROWING SIGNAL OF EXCESSIVE HEAT BUILDING INTO THE DESERT
SOUTHWEST, WHERE THIS TOOL INDICATES INCREASED CHANCES FOR TEMPERATURES
EXCEEDING THE 85TH PERCENTILE AND 110 DEGF.
AT THE BEGINNING OF WEEK-2 MODEL SOLUTIONS CONTINUE TO DEPICT A MID-LEVEL
TROUGH AND CUT-OFF LOW OVER THE GREAT LAKES, LEADING TO ENHANCED PRECIPITATION
FOR THE NORTHEAST CONUS. THE GEFS AND ECMWF PET BOTH INDICATE AT LEAST A 20%
CHANCE OF 3-DAY PRECIPITATION ACCUMULATIONS EXCEEDING THE 85TH PERCENTILE AND
AT LEAST A HALF INCH FOR PORTIONS OF THE NORTHEAST AND MID-ATLANTIC DURING THE
BEGINNING AND MIDDLE OF THE PERIOD. THE ECMWF IS A BIT STRONGER AND BROADER
WITH ITS COVERAGE WHILE THE GEFS IS A BIT WEAKER. A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED FOR AREAS WHERE THERE IS GOOD AGREEMENT BETWEEN THESE
PETS IN THE NORTHEAST AND MID-ATLANTIC FOR JUN 29-JUL 2. ACROSS THE CENTRAL
PLAINS AND MIDDLE-MISSISSIPPI VALLEY, PETS ARE INDICATING CHANCES OF 3-DAY
PRECIPITATION EXCEEDING THE 85TH PERCENTILE AND AN INCH. THIS IS A RELATIVELY
NEW FEATURE TO DEVELOP IN THE TOOLS AND THERE REMAIN DISAGREEMENTS ON THE
TIMING AND LOCATION OF ANY POTENTIAL HEAVY PRECIPITATION IN THESE REGIONS, THUS
NO ASSOCIATED HAZARD IS POSTED BUT THIS AREA WILL BE MONITORED. IN THE NORTHERN
PLAINS AND NORTHERN ROCKIES, PETS ARE LESS CONSISTENT REGARDING THE POTENTIAL
FOR EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 0.5 INCHES OF
PRECIPITATION. THEREFORE, THE HAZARD THAT HAD BEEN PREVIOUSLY POSTED IS
DISCONTINUED.
DROUGHT CONCERNS ARE FORECAST TO INCREASE ACROSS PARTS OF THE MIDWEST AS THE
HEAT OF SUMMER BUILDS AND A PERSISTENCE OF BELOW-NORMAL PRECIPITATION FORECAST
FOR THE REGION. THE POTENTIAL FOR RAPID ONSET DROUGHT (ROD) CONTINUES FOR MUCH
OF NORTHERN WISCONSIN IN TODAY’S OUTLOOK. SIGNIFICANT PRECIPITATION DEFICITS
HAVE BROUGHT THE POTENTIAL FOR ROD TO CENTRAL LOUISIANA AS WELL, AND WAS
INITIALLY HIGHLIGHTED LAST THURSDAY.
SNOWMELT SEASON CONTINUES ACROSS THE WESTERN CONUS AFTER ACCUMULATING A VERY
LARGE AND IN SOME CASES RECORD-BREAKING SNOWPACK, INDUCING RIVER FLOODING
ESPECIALLY ACROSS HIGHER ELEVATIONS FOR SOME AREAS IN THE WEST, WHERE A FEW
SITES STILL REPORT OVER 40 INCHES OF SNOW WATER CONTENT. AS SNOWMELT CONTINUES
IN PARTS OF THE SIERRA NEVADA, GREAT BASIN, AND NORTHERN ROCKIES, FLOODING MAY
CONTINUE TO OCCUR ALONG SOME RIVERS, AND IN AREAS ADJACENT TO THE HIGHER
ELEVATIONS. FLOODING IS ALSO EXPECTED TO CONTINUE ALONG THE JAMES RIVER IN
SOUTH DAKOTA AS RIVER LEVELS HAVE BEEN VERY SLOW TO RECEDE DUE TO SATURATED
GROUND CONDITIONS AND RELATIVELY FLAT TOPOGRAPHY.
FORECASTER: RYAN BOLT
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