826
FXUS21 KWNC 271847
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 27 2024
SYNOPSIS: EARLY IN WEEK-2, SURFACE HIGH PRESSURE IS FORECAST OFF THE SOUTHEAST
COAST, WITH SOUTHERLY RETURN FLOW OF VERY WARM, HUMID AIR EXPECTED OVER THE
CENTRAL AND EASTERN CONTIGUOUS U.S. (CONUS). A WEAK LOW PRESSURE SYSTEM AND ITS
TRAILING COLD FRONT MOVING ACROSS THIS PORTION OF THE NATION ARE LIKELY TO
TRIGGER SHOWERS AND THUNDERSTORMS, WITH THE HEAVIEST ACTIVITY EXPECTED FROM THE
NORTHEAST SOUTHWESTWARD TO THE CENTRAL APPALACHIANS. A BROAD AREA OF MID-LEVEL
HIGH PRESSURE IS FORECAST OVER THE SOUTH-CENTRAL STATES BEFORE EXPANDING
NORTHWESTWARD AND STRENGTHENING ACROSS MOST OF THE INTERIOR WEST. THIS WOULD
FAVOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE LOWER 48 STATES. A DEEP
MID-LEVEL LOW AND ENHANCED ONSHORE FLOW FAVORS ABOVE-NORMAL PRECIPITATION
ACROSS SOUTHEAST ALASKA.
HAZARDS
SLIGHT RISK FOR EXCESSIVE HEAT ACROSS PORTIONS OF THE RIO GRANDE VALLEY AND
ADJACENT PARTS OF TEXAS, TUE-MON, JUN 4-10.
SLIGHT RISK FOR EXCESSIVE HEAT ACROSS PORTIONS OF THE FLORIDA PENINSULA,
TUE-THU, JUN 4-6.
SLIGHT RISK FOR EXCESSIVE HEAT ACROSS THE CENTRAL VALLEY OF CALIFORNIA,
WED-MON, JUN 5-10.
SLIGHT RISK FOR HEAVY PRECIPITATION FROM THE NORTHEAST SOUTHWESTWARD TO THE
CENTRAL APPALACHIANS, TUE-SAT JUN 4-8.
SLIGHT RISK FOR HIGH WINDS FOR DOWNWIND AREAS OF THE NORTHERN ROCKY MOUNTAINS,
TUE-WED, JUN 4-5.
RAPID ONSET DROUGHT RISK ACROSS PARTS OF SOUTHERN TEXAS.
DETAILED SUMMARY
FOR THURSDAY MAY 30 - MONDAY JUNE 03:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JUNE 04 - MONDAY JUNE 10: THE GEFS, ECMWF ENSEMBLE MEAN (ECENS) AND
THE CANADIAN ENSEMBLE MEAN (CMCE) CONTINUE TO PREDICT AN UNSEASONABLY STRONG
SUBTROPICAL RIDGE OVER NORTHERN MEXICO AND INTO SOUTHERN TEXAS DURING THE
WEEK-2 PERIOD. IN THE VICINITY OF THE RIO GRANDE VALLEY, 500-HPA HEIGHTS ARE
PREDICTED TO RANGE BETWEEN 588-593 DM, WITH HEIGHT DEPARTURES RANGING BETWEEN
ZERO AND +60 METERS. THOUGH THE MOST INTENSE HEAT ASSOCIATED WITH THIS RIDGE IS
EXPECTED SOUTH OF THE U.S.-MEXICAN BORDER, MAXIMUM TEMPERATURES OF 100-106 DEG
F ARE ANTICIPATED ACROSS THE VICINITY OF THE RIO GRANDE VALLEY DURING THIS
PERIOD, WITH HEAT INDEX VALUES OF 105-110 DEG F. THE NATIONAL BLEND OF MODELS
(NBM) DEPICTS SEVERAL NEAR OR RECORD HIGH TEMPERATURES ACROSS THE RIO GRANDE
VALLEY EARLY IN WEEK-2. SIGNIFICANTLY MORE OVERNIGHT HIGH MINIMUM TEMPERATURE
RECORDS ARE EXPECTED TO BE TIED OR BROKEN, WITH LOWS ONLY DROPPING TO NEAR OR
SLIGHTLY ABOVE 80 DEG F. THE GEFS AND ECENS PROBABILISTIC EXTREMES TOOLS (
PETS) FORECAST AT LEAST A 20% CHANCE OF ACTUAL TEMPERATURES TO EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE AND 100 DEG F THROUGH MOST OF WEEK-2. A SKILL
WEIGHTED BIAS-CORRECTED APPARENT TEMPERATURE TOOL INDICATES AT LEAST A 20%
CHANCE FOR APPARENT TEMPERATURES (I.E., HEAT INDEX VALUES) TO EXCEED 110 DEG F.
THEREFORE, A SLIGHT RISK OF EXCESSIVE HEAT IS POSTED FOR ALL OF WEEK-2, JUN
4-10, FOR MIDDLE AND LOWER PORTIONS OF THE RIO GRANDE VALLEY.
IN CENTRAL AND SOUTHERN FLORIDA, THE GEFS AND ECENS PETS CONTINUE TO INDICATE
AT LEAST A 20% CHANCE FOR TEMPERATURES TO EXCEED THE 85TH PERCENTILE. A
SKILL-WEIGHTED, BIAS-CORRECTED GEFS/ECENS HYBRID TOOL INDICATES A 20 TO 40%
CHANCE OF APPARENT TEMPERATURES EXCEEDING 105 DEG F. THEREFORE, A SLIGHT RISK
OF EXCESSIVE HEAT REMAINS FORECAST ACROSS INLAND AREAS OF THE SOUTHERN HALF OF
THE FLORIDA PENINSULA.
AS THE WEEK-2 PERIOD PROGRESSES, 500-HPA HEIGHTS ARE PREDICTED BY THE THREE
ENSEMBLE MEANS TO RISE SIGNIFICANTLY ACROSS THE INTERIOR WEST, WITH THE
GREATEST DEPARTURES (HEIGHTS 120-180 METERS ABOVE NORMAL) EXPECTED ACROSS THE
NORTHWEST QUARTER OF THE CONUS. THIS WILL BE THE FIRST SIGNIFICANT HEAT OF THE
SEASON FOR THIS AREA AND IT WILL STAND OUT NOTICEABLY AGAINST THE RELATIVELY
COOL CONDITIONS EXPERIENCED SO FAR THIS SPRING. THE SNAKE RIVER VALLEY IN
SOUTHERN IDAHO AND PORTIONS OF THE COLUMBIA RIVER GORGE MAY TOP OUT AT OR
SLIGHTLY ABOVE 90 DEG F. HOWEVER, OVERNIGHT LOWS FORECAST NEAR 60 DEG F WILL
PROVIDE ADEQUATE RELIEF FROM THE DAYTIME HEAT. ELSEWHERE, EVEN WARMER
TEMPERATURES ARE EXPECTED FOR THE CENTRAL VALLEY OF CALIFORNIA, UNDER THE
STRENGTHENING MID-LEVEL RIDGE. A SLIGHT RISK OF EXCESSIVE HEAT IS POSTED FOR
THIS AREA FROM JUN 5-10, WITH DAYTIME HIGHS IN THE MID-UPPER 90S AND MAXIMUM
HEAT INDEX VALUES APPROACHING 105 DEG F.
AS FOR PRECIPITATION, THE UNCALIBRATED ECMWF AND VARIOUS PET GUIDANCE DEPICT
THE BEST CHANCE FOR 3-DAY PRECIPITATION AMOUNTS TO EXCEED 1-INCH, AND WHERE
THERE IS AT LEAST A 20% CHANCE OF THE 85TH HISTORICAL PERCENTILE BEING
EXCEEDED, IS OVER THE NORTHEAST AND CENTRAL PARTS OF THE APPALACHIANS, JUN 4-8.
THIS IS ASSOCIATED WITH THE EXPECTED APPROACH AND PASSAGE OF A LOW PRESSURE
SYSTEM AND TRAILING COLD FRONT MOVING THROUGH THE REGION. SHOWERS AND
THUNDERSTORMS ARE ALSO FORECAST TO CONTINUE WEST-SOUTHWESTWARD FROM THERE
ACROSS THE TENNESSEE VALLEY AND SOUTH-CENTRAL PLAINS NEAR WHERE THE FRONT IS
EXPECTED TO STALL. HOWEVER, THERE IS NOT QUITE ENOUGH SUPPORT BETWEEN THE
VARIOUS ENSEMBLE MEANS TO INCLUDE THIS ON THE MAP TODAY. TROPICAL MOISTURE
STREAMING NORTHEASTWARD FROM THE CENTRAL CARIBBEAN SEA IS FORECAST TO PASS
SOUTH AND EAST OF FLORIDA DURING WEEK-2, INFLUENCING PRIMARILY CUBA AND THE
BAHAMAS.
THERE IS A SLIGHT RISK OF HIGH WINDS (20-25 MPH) OVER AREAS DOWNWIND OF THE
NORTHERN ROCKIES, JUN 4-5, REASONABLY WELL SUPPORTED BY THE VARIOUS PET WIND
TOOLS. THIS IS ASSOCIATED WITH INCREASED WEST-SOUTHWEST FLOW ALOFT, AND WITH
WEAK LEE CYCLOGENESIS ANTICIPATED IN THIS AREA.
THE GREATEST RISK FOR RAPID ONSET DROUGHT (ROD) DURING EARLY TO MID 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.
MULTI-MODEL ENSEMBLE MEANS ARE IN VERY GOOD AGREEMENT THAT A DEEP 500-HPA
CLOSED LOW WILL BE LOCATED OVER THE GULF OF ALASKA BY THE START OF WEEK-2. THIS
ANOMALOUS MID-LEVEL TROUGH IS LIKELY TO ENHANCE ONSHORE FLOW TO SOUTHEAST
ALASKA WHERE ABOVE-NORMAL PRECIPITATION IS FAVORED. SINCE THE GEFS, ECENS, AND
CMCE PETS DEPICT PROBABILITIES OF ABOUT 20 PERCENT, BUT ACTUAL 3-DAY
PRECIPITATION AMOUNTS REMAIN BELOW THE 2-INCH HAZARDOUS THRESHOLD, A HEAVY
PRECIPITATION HAZARD IS NOT POSTED.
FORECASTER: ANTHONY ARTUSA
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