239
FXUS21 KWNC 231813
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 23 2024
SYNOPSIS: EARLY IN WEEK-2, A WEAK LOW PRESSURE SYSTEM AND TRAILING COLD FRONT
ARE FORECAST TO PROGRESS EASTWARD ACROSS THE GREAT PLAINS AND MISSISSIPPI
VALLEY. A BROAD AREA OF MID-LEVEL HIGH PRESSURE IS FORECAST TO STRENGTHEN OVER
THE SOUTH-CENTRAL CONTIGUOUS U.S. (CONUS) AT THE BEGINNING OF JUNE AND THEN
EXPAND NORTHWARD. THIS WOULD FAVOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE
LOWER 48 STATES WITH AN INCREASING CHANCE OF EXCESSIVE HEAT FOR TEXAS LATER IN
WEEK-2. A DEEP MID-LEVEL LOW AND ENHANCED ONSHORE FLOW FAVORS ABOVE-NORMAL
PRECIPITATION ACROSS ALASKA.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE CENTRAL AND SOUTHERN GREAT
PLAINS AND MISSISSIPPI VALLEY, FRI-SUN, MAY 31-JUN 2.
SLIGHT RISK OF EXCESSIVE HEAT FOR THE CENTRAL AND SOUTHERN FLORIDA PENINSULA,
FRI-SAT, MAY 31-JUN 1.
SLIGHT RISK OF EXCESSIVE HEAT FOR THE RIO GRANDE VALLEY AND PARTS OF SOUTHERN
AND WESTERN TEXAS, FRI-THU, MAY 31-JUN 6.
SLIGHT RISK OF EXCESS HEAT FOR NORTHERN AND EASTERN TEXAS, SOUTHERN OKLAHOMA,
AND NORTHWESTERN LOUISIANA, SUN-TUE, JUN 2-4.
RAPID ONSET DROUGHT RISK ACROSS SOUTHERN TEXAS.
DETAILED SUMMARY
FOR SUNDAY MAY 26 - THURSDAY MAY 30:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY MAY 31 - THURSDAY JUNE 06: THE GEFS AND ECMWF ENSEMBLE MEANS DEPICT
A SHORTWAVE 500-HPA TROUGH PROGRESSING EAST FROM THE WESTERN TO THE
NORTH-CENTRAL CONUS BY THE BEGINNING OF WEEK-2. THEIR DAILY FORECASTS ALSO
FEATURE A LOW PRESSURE SYSTEM TRACKING EAST FROM THE CANADIAN PRAIRIES TO
MANITOBA WITH A TRAILING COLD FRONT. THIS PREDICTED 500-HPA/SURFACE PATTERN IS
EXPECTED TO RESULT IN THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL ACROSS PARTS OF
THE GREAT PLAINS AND MISSISSIPPI VALLEY. THE SLIGHT RISK OF HEAVY PRECIPITATION
(MAY 31-JUNE 2) IS CONSISTENT WITH THE UNCALIBRATED ECMWF ENSEMBLE MEAN
PROBABILITIES FOR MORE THAN 1 INCH. SINCE PARTS OF THIS REGION HAVE SATURATED
SOILS FROM RECENT HEAVY RAINFALL, LOCALLY HEAVY RAINFALL MAY TRIGGER FLASH
FLOODING.
A STATIONARY FRONT IS FORECAST TO BECOME CENTERED OVER THE GULF OF MEXICO AND
CENTRAL FLORIDA PENINSULA LATE IN WEEK-1 TO THE BEGINNING OF WEEK-2. THE
PROXIMITY OF THIS FRONT AND ASSOCIATED CLOUDINESS ARE EXPECTED TO SLIGHTLY COOL
THE TEMPERATURES ACROSS FLORIDA. IN ADDITION, A WEAKER SUBTROPICAL RIDGE AND
SOUTHEASTERLY SURFACE FLOW MAY BEGIN TO PROMOTE A MORE ACTIVE SEA BREEZE REGIME
HEADING INTO JUNE. THEREFORE, THE MODERATE RISK OF EXCESSIVE HEAT FOR SOUTHERN
FLORIDA WAS DISCONTINUED. BASED ON CONTINUITY WITH PREVIOUS OUTLOOKS AND
SUPPORT FROM THE GEFS PROBABILISTIC EXTREMES TOOL (PET), A SLIGHT RISK OF
EXCESSIVE HEAT IS MAINTAINED ON MAY 31 AND JUNE 1.
FOLLOWING PREDICTED HEAT RELIEF FOR TEXAS DURING THE EARLY TO MIDDLE PART OF
NEXT WEEK, THE ECMWF ENSEMBLE MEAN IS BULLISH ON A STRENGTHENING SUBTROPICAL
RIDGE OVER NORTHERN MEXICO AND THE SOUTH-CENTRAL CONUS DURING THE FIRST WEEK OF
JUNE. INITIALLY, THE SLIGHT RISK OF EXCESSIVE HEAT IS DESIGNATED TO AREAS
CLOSER TO THE RIO GRANDE VALLEY. BY JUNE 2ND, THE GEFS, ECMWF, AND CANADIAN
ENSEMBLE MEANS DEPICT AN INCREASE IN 500-HPA HEIGHTS OVER THE SOUTH-CENTRAL
CONUS IMPLYING AN INCREASING CHANCE OF EXCESSIVE HEAT. THE ECMWF ENSEMBLE MEAN
HAS 500-HPA HEIGHTS OF 588 DAM EXPANDING NORTH THROUGH OKLAHOMA AND ARKANSAS.
THE NORTHWARD EXPANSION OF THE SLIGHT RISK OF EXCESSIVE HEAT TO SOUTHERN
OKLAHOMA AND NORTHWESTERN LOUISIANA GENERALLY FOLLOWED A SKILL-WEIGHTED
GEFS/ECMWF TOOL WHERE A 20 TO 40 PERCENT CHANCE OF HEAT INDEX VALUES EXCEEDING
105 DEGREES F IS PREDICTED. THIS EXCESSIVE HEAT HAZARD IS VALID FROM JUNE 2 TO
4 AS THERE IS MORE UNCERTAINTY ON THE PLACEMENT OF THE 500-HPA RIDGE AXIS AND
LARGE ENSEMBLE SPREAD TOWARDS THE END OF WEEK-2.
THE GREATEST RISK FOR RAPID ONSET DROUGHT (ROD) DURING THE REMAINDER OF MAY
INTO EARLY JUNE EXISTS FOR SOUTHERN TEXAS. THE ROD HAZARD IS BASED ON 30 TO
60-DAY PRECIPITATION DEFICITS, LOW SOIL MOISTURE, AND LIKELIHOOD OF
ABOVE-NORMAL TEMPERATURES ALONG WITH THE LACK OF A STRONG WET SIGNAL DURING THE
NEXT TWO WEEKS. SINCE MODERATE SHORT-TERM DROUGHT IS NOW DESIGNATED FOR MUCH OF
SOUTHERN FLORIDA IN THE U.S. DROUGHT MONITOR AND THERE ARE SIGNS FOR AT LEAST
NEAR NORMAL PRECIPITATION DURING AN INCREASINGLY WET TIME OF YEAR, THE ROD
HAZARD WAS DISCONTINUED FOR THAT AREA.
MULTI-MODEL ENSEMBLE MEANS ARE IN EXCELLENT AGREEMENT THAT A DEEP 500-HPA
CLOSED LOW DEVELOPS OVER THE ALEUTIANS AND SOUTHWESTERN ALASKA BY THE BEGINNING
OF JUNE. THIS ANOMALOUS MID-LEVEL TROUGH IS LIKELY TO ENHANCE ONSHORE FLOW TO
SOUTHERN ALASKA WHERE ABOVE-NORMAL PRECIPITATION IS FAVORED. SINCE THE GEFS AND
ECMWF PETS DEPICT PROBABILITIES OF LESS THAN 20 PERCENT FOR 3-DAY PRECIPITATION
AMOUNTS EXCEEDING 2 INCHES, A HEAVY PRECIPITATION HAZARD IS NOT POSTED.
FORECASTER: BRAD PUGH
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