411
FXUS21 KWNC 311920
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 31 2024
SYNOPSIS: STRONG AND PERSISTENT MID-LEVEL HIGH PRESSURE IS EXPECTED TO INCREASE
CHANCES FOR AN EXTENDED PERIOD OF EXCESSIVE HEAT TO MUCH OF THE WESTERN
CONTIGUOUS U.S. (CONUS). THIS IS LIKELY TO BE THE FIRST SIGNIFICANT HEAT EVENT
OF THE SEASON FOR A LARGE PART OF THIS REGION, ESPECIALLY ACROSS THE
NORTHWESTERN CONUS WHICH HAS EXPERIENCED A RELATIVELY COOL SPRING TO DATE.
HAZARDS
MODERATE RISK FOR EXCESSIVE HEAT FOR A LARGE PORTION OF THE INTERIOR WEST,
SAT-TUE, JUN 8-11.
SLIGHT RISK FOR EXCESSIVE HEAT IN MOST AREAS FROM THE ROCKIES TO THE PACIFIC
COAST, SAT-FRI, JUN 8-14.
SLIGHT RISK FOR EXCESSIVE HEAT IN SOUTHERN TEXAS, WED-FRI, JUN 12-14.
SLIGHT RISK FOR EXCESSIVE HEAT IN FLORIDA, SAT-FRI, JUN 8-14.
SLIGHT RISK FOR HEAVY PRECIPITATION OVER THE NORTHEAST AND MID-ATLANTIC COASTAL
PLAIN, SAT-TUE, JUN 8-11.
SLIGHT RISK FOR HEAVY PRECIPITATION OVER SOUTH-CENTRAL PORTIONS OF THE GREAT
PLAINS AND MISSISSIPPI VALLEY, SAT-TUE, JUN 8-11.
SLIGHT RISK FOR EPISODES OF HIGH WINDS ACROSS MUCH OF THE TEXAS BIG BEND,
SOUTHERN PORTIONS OF THE FOUR CORNERS STATES, AND SOUTHERN CALIFORNIA, SAT-FRI,
JUN 8-14.
RAPID ONSET DROUGHT RISK ACROSS PARTS OF SOUTHERN TEXAS.
RAPID ONSET DROUGHT RISK OVER THE CENTRAL FLORIDA PENINSULA.
DETAILED SUMMARY
FOR MONDAY JUNE 03 - FRIDAY JUNE 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JUNE 08 - FRIDAY JUNE 14: THE GEFS, ECMWF ENSEMBLE MEAN (ECENS)
AND THE CANADIAN ENSEMBLE MEAN (CMCE) ALL SHOW A MODERATE TO STRONG MID-LEVEL
RIDGE OVER THE WESTERN LOWER 48 STATES AT THE ONSET OF WEEK-2, WITH THE GEFS
BEING SLIGHTLY WEAKER AND DISPLACED FARTHER EAST THAN THE OTHER TWO ENSEMBLE
MEAN SOLUTIONS. ACCORDING TO THE ECENS AND CMCE, MAXIMUM 500-HPA HEIGHTS ARE
FORECAST TO RANGE BETWEEN 582-590 DM, WITH MAXIMUM HEIGHT DEPARTURES AT LEAST
180 METERS ABOVE NORMAL. THE GEFS DEPICTS SLIGHTLY LOWER HEIGHTS AND REDUCED
HEIGHT DEPARTURES ACROSS THE NORTHWEST, RELATIVE TO THE OTHER TWO ENSEMBLE MEAN
MODELS. BY DAYS 10-11, ON THE SOUTH SIDE OF THIS LARGE ANOMALOUS RIDGE, ALL
THREE MODEL SOLUTIONS FORECAST 500-HPA HEIGHTS THAT ARE CLOSE TO NORMAL ACROSS
THE FAR SOUTHERN INTERMOUNTAIN WEST AND SOUTHERN CALIFORNIA. DURING THE LATTER
HALF OF WEEK-2, THE HEIGHT ANOMALIES ACROSS THE NORTHWESTERN QUARTER OF THE
CONUS ARE FORECAST TO GRADUALLY DIMINISH, WHICH SIGNALS THE WINDING DOWN OF
THIS FIRST SIGNIFICANT HEAT EVENT OF THE SEASON.
SURFACE TEMPERATURES ARE EXPECTED TO CLIMB INTO THE 90’S ACROSS THE INTERIOR
NORTHWEST. MID-UPPER 90’S (POSSIBLY EVEN 100 DEG F) ARE DEPICTED BY THE 0Z
UNCALIBRATED ECENS MODEL TEMPERATURES ACROSS THE TYPICALLY WARMER LOCALES OF
THE SNAKE RIVER VALLEY IN IDAHO AND EASTERN SECTIONS OF WASHINGTON AND OREGON
DURING THE PEAK OF THE EXPECTED HEAT WAVE, JUN 8-11. A MODERATE RISK (40-60%
CHANCE) OF EXCESSIVE HEAT IS POSTED FOR MUCH OF THE INTERIOR WEST (VALID JUN
8-11) DUE TO THE EXPECTED ELEVATED AIR TEMPERATURES AND SOMEWHAT ELEVATED
LEVELS OF HUMIDITY. A SLIGHT RISK (20-40% CHANCE) OF EXCESSIVE HEAT IS POSTED
FOR NEARLY ALL OF THE INTERIOR WEST, WITH THE EXCEPTION OF FAR SOUTHERN AREAS
ALONG THE MEXICAN BORDER, VALID FOR THE ENTIRE WEEK-2 PERIOD. ACROSS
CALIFORNIA’S CENTRAL VALLEY, THE PEAK HEAT IS ANTICIPATED DURING THE DAYS 3-7
TIMEFRAME, WITH A SLOW DECLINE IN TEMPERATURES DURING THE EARLY DAYS OF THE
WEEK-2 OUTLOOK PERIOD. THE HIGHEST TEMPERATURES INDICATED BY THE 0Z
UNCALIBRATED ECENS RANGE FROM 100-105 DEG F ACROSS THE SAN JOAQUIN AND TULARE
VALLEYS, AND 95-100 DEG F FOR THE SACRAMENTO VALLEY ON DAY 8. THESE DAYTIME
HIGH TEMPERATURES ARE EXPECTED TO SLOWLY RAMP DOWN ABOUT 5-10 DEGREES OVER THE
ENSUING FEW DAYS. THE NATIONAL BLEND OF MODELS (NBM) DOES NOT SHOW NEAR OR
RECORD HIGHS FOR THE CENTRAL VALLEY BEYOND DAY 7.
THE ANTICIPATED PASSAGE OF A WEAK COLD FRONT ACROSS SOUTHERN TEXAS AT THE
BEGINNING OF WEEK-2, COMBINED WITH A SLIGHT REDUCTION IN REGIONAL 500-HPA
HEIGHTS, FAVORS A BRIEF RESPITE FROM THE HEAT AND HUMIDITY EXPERIENCED DURING
THE PAST WEEK OR TWO. AIR TEMPERATURES ARE FORECAST TO RANGE FROM THE MID-UPPER
90’S DURING DAYS 8-11, AND REACH THE LOW 100’S DURING THE LAST FEW DAYS OF
WEEK-2. AN UNCALIBRATED EXCESSIVE HEAT TOOL THAT SKILL-WEIGHTS AND BIAS
CORRECTS GEFS AND ECENS HYBRID FORECASTS OF DRY BULB TEMPERATURE AND HUMIDITY
FAVORS HEAT INDEX VALUES IN EXCESS OF 110 DEG F ACROSS FAR SOUTHERN TEXAS,
IMPLYING A SIGNIFICANT CONTRIBUTION OF THE EXPECTED EXCESSIVE HEAT IS COMING
FROM HIGHER HUMIDITY LEVELS. ACCORDINGLY, A SLIGHT RISK OF EXCESSIVE HEAT IS
INDICATED FOR THE CENTRAL AND LOWER RIO GRANDE VALLEY FOR JUN 12-14. A SLIGHT
RISK FOR EXCESSIVE HEAT IS ALSO DEPICTED ACROSS FLORIDA FOR THE DURATION OF
WEEK-2. THE NBM TOOL INDICATES NEAR TO RECORD HIGH TEMPERATURES (93-96 DEG F)
FOR PARTS OF THE STATE EARLY IN WEEK-2 AND THE UNCALIBRATED EXCESSIVE HEAT TOOL
NOTED EARLIER DEPICTS HEAT INDEX VALUES IN EXCESS OF 105 DEG F ACROSS THIS
REGION.
FOR PRECIPITATION, THERE ARE TWO AREAS WHERE A SLIGHT CHANCE OF HEAVY
PRECIPITATION IS POSTED. ONE AREA INCLUDES THE COASTAL PLAIN OF THE NORTHEAST
AND MID-ATLANTIC REGION (JUN 8-11), AND THE OTHER AREA INCLUDES SOUTH-CENTRAL
PORTIONS OF THE GREAT PLAINS AND MISSISSIPPI VALLEY, FOR THE SAME PERIOD JUN
8-11. THESE AREAS HIGHLIGHT WHERE THERE IS AT LEAST A 20% CHANCE OF 3-DAY
RAINFALL TOTALS EXCEEDING THE 85TH HISTORICAL PERCENTILE AND ONE INCH. BOTH
AREAS ARE ASSOCIATED WITH PREDICTED FRONTAL ACTIVITY, WITH THE LATTER EXPECTED
TO HAVE AN ADDITIONAL CONTRIBUTION FROM THUNDERSTORM COMPLEXES. NEAR THE END OF
WEEK-2, THE THREE ENSEMBLE MEAN SOLUTIONS DEPICT PRECIPITATION TO BE MORE
FOCUSED IN THE GENERAL VICINITY OF FLORIDA, WHICH COULD ENTAIL THE DEVELOPMENT
OF A TROPICAL SYSTEM. HOWEVER, AT THIS TIME RANGE CONFIDENCE IS QUITE LOW. THE
POSSIBILITY OF SUCH AN EVENT WILL BE MONITORED NEXT WEEK.
PROBABILISTIC EXTREMES TOOL (PET) WIND GUIDANCE FROM THE ECENS FAVORS A SLIGHT
RISK FOR PERIODS OF HIGH WINDS (AT LEAST 20 MPH) FOR THE WEEK-2 PERIOD. THE
RISK AREA INCLUDES PARTS OF SOUTHERN CALIFORNIA, SOUTHERN PORTIONS OF THE FOUR
CORNERS REGION, AND FAR WESTERN TEXAS. LITTLE TO NO RAINFALL, HOT TEMPERATURES,
AND EASTERLY WINDS FAVOR AN INCREASED RISK OF WILDFIRES ACROSS THESE AREAS.
PRECIPITATION DEFICITS OVER THE PAST 30- AND 60-DAYS, HIGH RATES OF
EVAPOTRANSPIRATION (ET), AND THE CONTINUED FORECAST OF HIGH HEAT AND SUBNORMAL
PRECIPITATION ACROSS FLORIDA AND SOUTHERN TEXAS IS EXPECTED TO PROMOTE RAPID
DROUGHT DEVELOPMENT ACROSS PARTS OF THESE AREAS.
FORECASTER: ANTHONY ARTUSA
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