401
FXUS21 KWNC 131821
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 13 2024
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST TO EXPAND ACROSS THE SOUTHERN
TIER OF THE CONTIGUOUS U.S. (CONUS) EARLY IN WEEK-2. THIS FAVORS A RELATIVELY
DRIER PATTERN COMPARED TO WEEK-1, BUT WITH INCREASING CHANCES FOR ANOMALOUSLY
WARM TEMPERATURES, AND EXCESSIVE HEAT CONDITIONS POSSIBLY AFFECTING PARTS OF
SOUTHERN TEXAS AND THE FLORIDA PENINSULA. MID-LEVEL LOW PRESSURE IS FORECAST
ACROSS THE NORTHWESTERN AND NORTH-CENTRAL CONUS, WHICH MAY HELP MODERATE
TEMPERATURES OVER SOME AREAS BY THE MIDDLE OF THE PERIOD AS MID-LEVEL HEIGHTS
DECREASE. A FRONTAL SYSTEM PREDICTED TO MOVE SOUTHWARD ACROSS THE CENTRAL CONUS
MAY LEAD TO INCREASED CHANCES FOR HEAVY PRECIPITATION, INITIALLY ACROSS THE
CENTRAL PLAINS AND MIDDLE MISSISSIPPI VALLEY, AND SHIFTING SOUTHWARD TOWARD THE
GULF COAST BY THE MIDDLE OF WEEK-2.
HAZARDS
MODERATE RISK FOR EXCESSIVE HEAT ACROSS SOUTHERN TEXAS, TUE-THU, MAY 21-23.
SLIGHT RISK FOR EXCESSIVE HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY, TUE-MON, MAY 21-27.
SLIGHT RISK FOR EXCESSIVE HEAT ACROSS THE SOUTHERN FLORIDA PENINSULA, TUE-MON,
MAY 21-27.
SLIGHT RISK FOR HEAVY PRECIPITATION ACROSS PORTIONS OF THE GREAT PLAINS,
MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, AND SOUTHEAST, TUE-SAT, MAY 21-25.
RAPID ONSET DROUGHT RISK ACROSS THE SOUTHERN FLORIDA PENINSULA.
DETAILED SUMMARY
FOR THURSDAY MAY 16 - MONDAY MAY 20:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 21 - MONDAY MAY 27: SUBTROPICAL RIDGING IS FORECAST TO EXPAND
ACROSS PORTIONS OF THE SOUTH-CENTRAL CONUS HEADING INTO THE WEEK-2 PERIOD. THIS
FAVORS INCREASING CHANCES FOR ANOMALOUSLY WARM TEMPERATURES STRETCHING FROM THE
CENTRAL AND SOUTHERN PLAINS EASTWARD TO THE SOUTHERN MID-ATLANTIC AND SOUTHEAST
COASTS. GIVEN THE TIME OF YEAR, MANY AREAS AWAY FROM THE GULF COAST ARE NOT
EXPECTED TO HAVE TEMPERATURES REACH EXCESSIVE HEAT CRITERIA. THE STRONGEST
SIGNALS FOR EXCESSIVE HEAT ARE ACROSS PORTIONS OF TEXAS WHERE THE GEFS AND
ECMWF PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT AT LEAST A 20 PERCENT CHANCE
FOR MAXIMUM TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 90
DEG F. PROBABILITIES INCREASE ABOVE 40 PERCENT ACROSS PORTIONS OF SOUTHERN AND
SOUTHWESTERN TEXAS, WITH INCREASING CHANCES FOR TRIPLE DIGIT TEMPERATURES. THE
NATIONAL BLEND OF MODELS DEPICTS AN ELEVATED POTENTIAL FOR DAILY RECORD
TEMPERATURES, WITH SOME AREAS NEAR OR EXCEEDING 105 DEG F, AND THE ECMWF/GEFS
SKILL WEIGHTED HEAT RISK GUIDANCE INDICATES AT LEAST A 30 PERCENT CHANCE HEAT
INDICES EXCEED 110 DEG F ACROSS SOUTHERN TEXAS. GIVEN THESE SIGNALS, A MODERATE
RISK FOR EXCESSIVE HEAT IS POSTED ACROSS SOUTH TEXAS FOR 5/21-5/23, WITH A
BROADER SLIGHT RISK CONTINUING ACROSS MUCH OF THE REMAINDER OF TEXAS (EXCLUDING
THE NORTHERN PORTION AND THE PANHANDLE), SOUTHEASTERN NEW MEXICO, AND THE LOWER
MISSISSIPPI VALLEY FOR ALL OF WEEK-2. FOR THE WESTERN SIDE OF THE SLIGHT RISK
AREA, HEAT IS LIKELY TO BE TEMPERATURE DRIVEN, BUT HIGHER DEWPOINTS FAVORED
ACROSS EASTERN TEXAS AND THE LOWER MISSISSIPPI VALLEY MAY PUSH HEAT INDICES
ABOVE 105 DEG F DESPITE THE RELATIVELY LOWER TEMPERATURES COMPARED TO THOSE
FURTHER WEST. THE SLIGHT RISK FOR EXCESSIVE HEAT ALSO INCLUDES THE SOUTHERN
FLORIDA PENINSULA FOR ALL OF WEEK-2. WHILE TEMPERATURE SIGNALS ARE NOT AS
STRONG COMPARED TO TEXAS, HUMIDITY IS FORECAST TO BE MORE OF A FACTOR. ACTUAL
HIGH TEMPERATURES IN THE LOW- TO MID-90S ARE POSSIBLE, WITH ELEVATED DEWPOINTS
POSSIBLY LEADING TO HEAT INDICES ABOVE 105 DEG F IN SOME AREAS.
TROUGHING FORECAST ACROSS THE NORTHWESTERN AND NORTH-CENTRAL CONUS FAVORS
BELOW-NORMAL TEMPERATURES ACROSS MUCH OF THE WEST, EXTENDING INTO PARTS OF THE
NORTHERN AND CENTRAL PLAINS AND UPPER AND MIDDLE MISSISSIPPI VALLEY. THE
RESULTING TEMPERATURE CONTRAST IS LIKELY TO LEAD TO ENHANCED FRONTAL ACTIVITY
ACROSS THE CENTRAL PLAINS AND MIDDLE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS
EARLY IN WEEK-2. THE ECMWF PET INDICATES AT LEAST A 20 PERCENT CHANCE 3-DAY
PRECIPITATION TOTALS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH OVER
THESE AREAS. BY THE MIDDLE OF WEEK-2, THIS FRONTAL ACTIVITY IS FORECAST TO
SHIFT MORE SOUTHWARD, WITH BOTH THE GEFS AND ECMWF PETS INDICATING THE SAME
PROBABILITIES ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND CENTRAL GULF
COAST REGION. A SLIGHT RISK FOR HEAVY PRECIPITATION IS POSTED ACROSS PORTIONS
OF THE GREAT PLAINS, MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, AND SOUTHEAST
FOR 5/21-5/25. MORE NORTHERN AREAS OF THIS SHAPE ARE FAVORED TO RECEIVE HEAVY
RAINFALL EARLY, WITH THE RISK MOVING SOUTHWARD WITH TIME. THE SOUTHWARD MOVING
FRONT AND SUBSEQUENT DECREASING MID-LEVEL HEIGHTS MAY ALSO MODERATE
TEMPERATURES OVER SOME AREAS, ALTHOUGH MODELS DEPICT THE RIDGING EXPANDING
AGAIN BY THE END OF WEEK-2 SO THIS COOLING WOULD LIKELY BE BRIEF. THE FLOODING
POSSIBLE AREA IS REMOVED ALONG THE GULF COAST AND SOUTHEAST GIVEN THE
RELATIVELY DRIER CONDITIONS FAVORED TO DEVELOP LATE IN THE WEEK-1 PERIOD, BUT
THIS AREA WILL CONTINUE TO BE MONITORED GIVEN THE INCREASING PRECIPITATION
POTENTIAL IN THE MIDDLE OF WEEK-2. DECREASING SOIL MOISTURE AND A MORE
SOUTHWARD DISPLACEMENT FROM THE PREDICTED HEAVIEST RAINFALL IN WEEK-1 LEAD TO
AN ELEVATED RAPID ONSET DROUGHT RISK ACROSS PARTS OF SOUTHERN FLORIDA DUE TO
THE WARM AND DRY PATTERN PREDICTED IN WEEK-2.
NO HAZARDS ARE ISSUED FOR ALASKA, WITH NEAR- TO BELOW-NORMAL TEMPERATURES
FAVORED FOR MOST OF THE STATE. SNOWMELT SEASON IS UNDERWAY AND FROZEN RIVERS
ARE BEGINNING TO BREAK UP, LEADING TO THE POTENTIAL FOR RIVER FLOODING RELATED
TO ICE-JAMS. HOWEVER, THERE ARE NO INDICATIONS OF IMPENDING MAJOR RIVER
BREAK-UPS OR SERIOUS THREAT OF ICE-JAMMING SO NO FLOODING-RELATED HAZARDS ARE
POSTED AT THIS TIME. CAUTION WILL CONTINUE TO BE EXERCISED AS RIVER BREAK-UP
CAN BE UNPREDICTABLE AND LOCAL CONDITIONS CAN CHANGE QUICKLY.
FORECASTER: THOMAS COLLOW
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