107
FXUS21 KWNC 211923
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 21 2026
SYNOPSIS: PERSISTENT MID-LEVEL HIGH PRESSURE IS EXPECTED TO BRING AN ELEVATED
RISK OF EXTREME HEAT TO A LARGE PORTION OF THE CONTIGUOUS U.S. (CONUS) FROM THE
OHIO AND TENNESSEE VALLEYS AND SOUTHEAST WESTWARD TO THE WEST. HOT WEATHER AND
NEAR OR BELOW NORMAL RAINFALL BRING AN INCREASED RISK OF RAPID ONSET DROUGHT TO
PART OF THE NORTHERN GREAT PLAINS. IN THE WEST, THE MONSOONAL CIRCULATION MAY
BE PERIODICALLY ROBUST WITH LOCALIZED ENHANCED RAINFALL, BUT DUE TO HIGH
UNCERTAINTY NO ASSOCIATED PRECIPITATION HAZARD IS DESIGNATED AT THIS TIME.
ADDITIONALLY, ENHANCED MOIST FLOW ASSOCIATED WITH THE MONSOON MAY INCREASE
HUMIDITY AND RESULTING INCREASED HEAT INDEX VALUES ACROSS PARTS OF THE WEST.
ONE OR MORE TROPICAL CYCLONES MIGHT ALSO IMPACT HAWAII, RAISING THE POTENTIAL
FOR HEAVY PRECIPITATION AND GUSTY WINDS. MEANWHILE, A POSSIBLE SURFACE LOW
TRACKING ACROSS THE EASTERN U.S./CANADIAN BORDER AND ASSOCIATED WAVERING
FRONTAL BOUNDARY ACROSS THE SOUTHEASTERN CONUS AND SOUTHERN MID-ATLANTIC
SUPPORTS A SLIGHT RISK OF HEAVY PRECIPITATION FOR THESE REGIONS UNTIL THE
MIDDLE OF WEEK-2.
HAZARDS
HIGH RISK OF EXTREME HEAT FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, AND
LOWER MISSISSIPPI VALLEY, WED-THU, JUL 29-30.
MODERATE RISK OF EXTREME HEAT FOR MUCH OF THE GREAT PLAINS AND ADJACENT PARTS
OF THE MISSISSIPPI VALLEY, CENTRAL GREAT BASIN, AND THE SOUTHWEST, WED-FRI, JUL
29-31.
SLIGHT RISK OF EXTREME HEAT FOR MANY PARTS OF THE GULF COAST AND FLORIDA, OHIO
AND TENNESSEE, AND MISSISSIPPI VALLEYS, GREAT PLAINS, CENTRAL AND SOUTHERN
ROCKIES, GREAT BASIN, SOUTHWEST, AND CALIFORNIA VALLEY, WED-TUE, JUL 29-AUG 4.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE CENTRAL GULF COAST, PART OF THE
SOUTH ATLANTIC REGION, AND THE EASTERN CAROLINAS, WED-SAT, JUL 29-AUG 1.
RAPID ONSET DROUGHT (ROD) POSSIBLE FOR PART OF THE NORTHERN GREAT PLAINS.
DETAILED SUMMARY
FOR FRIDAY JULY 24 - TUESDAY JULY 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JULY 29 - TUESDAY AUGUST 04: MODELS CONTINUE TO BE IN GOOD
AGREEMENT FEATURING A PERSISTENT AMPLIFIED 500-HPA RIDGING OVER THE WESTERN AND
CENTRAL CONUS AND TROUGHING ACROSS THE NORTHEASTERN REGION. RIDGING IS
GENERALLY MORE AMPLIFIED ACROSS THE MODELS COMPARED TO YESTERDAY, CENTERED OVER
THE FOUR CORNERS REGION AND EXPANDING WESTWARD WITH TIME. THE RIDGE IS
ANTICIPATED TO BE LOCATED INITIALLY FOCUSED ACROSS THE CENTRAL CONUS BEFORE
EXPANDING WESTWARD BY WEEK-2. TROUGHING ACROSS THE NORTHWEST IS INITIALLY
ANTICIPATED TO LINGER FROM WEEK-1 INTO THE ONSET OF WEEK-2 BUT TRANSITION TO
RIDGING WITH THE WESTWARD EXPANSION EARLY IN THE PERIOD. THIS FEATURE FAVORS AN
INCREASED RISK OF EXTREME HEAT ACROSS LARGE PARTS OF THE WESTERN, CENTRAL, AND
SOUTHERN CONUS.
UNDERNEATH THE RIDGING ALOFT, AN ELEVATED POTENTIAL FOR HEAT RISK CONTINUES TO
BE SUPPORTED BY A NUMBER OF TEMPERATURE AND HEAT TOOLS ACROSS MANY PARTS OF THE
SOUTHERN, WESTERN, AND CENTRAL CONUS. HIGHER THAN NORMAL DEWPOINTS ARE ALSO
FAVORED EAST OF THE ROCKIES DUE TO A LONG FETCH OF GULF MOISTURE NEAR THE
SURFACE, INCREASING DEW POINTS AND HELPING TO DRIVE UP HEAT INDEX VALUES ACROSS
SOME PARTS OF THE EAST-CENTRAL CONUS AND SOUTHEAST. DUE TO THE MORE AMPLIFIED
RIDGE FORECAST AND INCREASING SIGNALS FOR HEAT, A HIGH RISK (>60% CHANCE) OF
EXTREME HEAT HAS BEEN DESIGNATED ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS, AND LOWER MISSISSIPPI VALLEY JUL 29-30, WHERE AND WHEN THERE ARE
SIGNIFICANT CHANCES IN HEAT TOOLS AND PETS FOR EXTREME HEAT. A MODERATE RISK
(40-60% CHANCE) IS POSTED FOR JUL 29-31, WITH COVERAGE EXPANDED TO INCLUDE MORE
OF THE MISSISSIPPI VALLEY, GREAT PLAINS, SOUTHWEST, AND GREAT BASIN. A BROAD
SURROUNDING AREA IS HIGHLIGHTED WITH A SLIGHT RISK, THROUGHOUT WEEK-2, WITH
SLIGHT INCREASE IN COVERAGE TO THE CENTRAL GREAT BASIN AND CALIFORNIA CENTRAL
VALLEY. ADDITIONALLY, ENHANCED MOISTURE FROM THE SOUTHWEST MONSOON MAY BRING
INCREASED HUMIDITY TO PARTS OF THE WEST THAT COULD INCREASE HEAT INDEX VALUES.
ANOMALOUSLY HIGH SSTS IN THE WATERS ADJACENT TO THE GULF AND SOUTH ATLANTIC
COASTS ARE EXPECTED TO CONTRIBUTE TO HEAT AND HUMIDITY EAST OF THE ROCKIES.
ABSOLUTE TEMPERATURES OR HEAT INDEX VALUES MAY REACH 105 DEG F ACROSS PARTS OF
THE CALIFORNIA CENTRAL VALLEY, GULF COAST, AND FLORIDA, 105 TO 110 DEG F ACROSS
THE GREAT PLAINS AND LOWER MISSISSIPPI VALLEY, AND 115 DEG F ACROSS THE DESERT
SOUTHWEST. ACCORDING TO THE NATIONAL BLEND OF MODELS (NBM), SOUTHERN PORTIONS
OF THE HEAT RISK AREA SUCH AS THE DESERT SOUTHWEST, SOUTHERN PLAINS, GULF
COAST AND FLORIDA MAY EXPERIENCE NEAR OR RECORD BREAKING HIGH NIGHTTIME
TEMPERATURES IN THE UPPER 70S TO LOW 80S, WHICH WOULD PROVIDE LITTLE OVERNIGHT
RELIEF. IN GENERAL THE ECENS PET IS NOT AS ROBUST WITH THE ODDS FOR EXTREME
HEAT COMPARED TO THE GEFS ACROSS THE WEST BUT HAS INCREASED PROBABILITIES FOR
HEAT ACROSS THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY.
SURFACE LOWS ARE POSSIBLE ACROSS THE INTERIOR WEST DURING WEEK-2, WHICH COULD
SUPPORT PERIODS OF GUSTY CONDITIONS. THERE IS INSUFFICIENT CERTAINTY REGARDING
THE SPECIFICS OF HIGH WINDS TO DESIGNATE A HIGH WIND HAZARD. REGARDLESS, THE
COMBINATION OF HOT TEMPERATURES, DRY CONDITIONS, AND WIND GUSTS COULD LEAD TO
ENHANCED WILDFIRE RISK ACROSS THE WEST, ESPECIALLY ACROSS AREAS ALREADY
EXPERIENCING ACTIVE WILDFIRES.
ANTECEDENT DRYNESS, ANOMALOUS WARMTH AND DRYNESS DURING WEEK-1, AND THE
POTENTIAL FOR EXTREME HEAT DURING WEEK-2 SUPPORT AN ENHANCED RISK OF RAPID
ONSET DROUGHT (ROD) ACROSS PORTIONS OF THE NORTHERN PLAINS. THE ANTICIPATED
HEAT IS EXPECTED TO OVERWHELM ANY SHORT-LIVED RELIEF THAT MAY OCCUR.
WEEK-2 IS EXPECTED TO BE AN ACTIVE PERIOD OF TROPICAL ACTIVITY IN THE EASTERN
PACIFIC. MORE THAN ONE TROPICAL CYCLONE IS EXPECTED, AND MODELS HAVE
CONSISTENTLY SHOWN AT LEAST ONE OF THESE SYSTEMS MOVING FAR ENOUGH TOWARD THE
CENTRAL PACIFIC TO THREATEN HAWAII WITH HEAVY RAIN AND HIGH WINDS. PLEASE REFER
TO THE NATIONAL HURRICANE CENTER (NHC) FOR THE LATEST TROPICAL DEVELOPMENTS.
DESPITE THE STRONG MID-LEVEL RIDGE FAVORED ACROSS THE WESTERN CONUS, THE
FORECAST POSITION OF THE RIDGE CENTER DOES NOT SUPPORT AN EXTREME ADVECTION OF
MONSOONAL MOISTURE INTO THE REGION, ALTHOUGH MODEL FORECASTS AND THE PETS TODAY
SHOW SLIGHTLY HIGHER LIKELIHOOD THAN YESTERDAY. IN ADDITION, IT IS POSSIBLE
THAT ONE OR MORE OF THE TROPICAL CYCLONES EXPECTED IN THE EASTERN PACIFIC COULD
TRACK NORTHWARD AND CONTRIBUTE TO A SURGE OF TROPICAL MOISTURE INTO THE REGION,
WHICH WOULD SIGNIFICANTLY ENHANCE RAINFALL AMOUNTS. RAW MODEL OUTPUT AND THE
PETS AREN'T SUFFICIENTLY ROBUST TO SUPPORT ANY SLIGHT HEAVY PRECIPITATION RISK
FROM BEING POSTED, BUT WITH THE TOOLS TRENDING WETTER AND THE POTENTIAL FOR
TROPICAL MOISTURE INCURSION, THE SITUATION WILL NEED TO BE CLOSELY MONITORED.
MULTIPLE MODELS INDICATE A SURFACE LOW TRACKING ALONG THE EASTERN U.S./CANADIAN
BORDER AT THE BEGINNING OF WEEK-2, WITH AN ASSOCIATED WAVERING FRONTAL BOUNDARY
NEAR THE CENTRAL GULF AND SOUTH ATLANTIC COASTAL REGIONS IN CONJUNCTION WITH
THE MID-LEVEL TROUGHING FAVORED OVER THE EASTERN U.S. THIS PATTERN SUPPORTS
SLIGHT RISK OF HEAVY PRECIPITATION TO PARTS OF THE CENTRAL GULF COAST, SOUTH
ATLANTIC REGION, AND EASTERN CAROLINAS, JUL 29-AUG 1. THERE IS UNCERTAINTY
ABOUT HOW MUCH RAINFALL OCCURS OVER THE LAND VERSUS OFFSHORE, THUS ONLY A
SLIGHT RISK IS DESIGNATED. THERE IS CURRENTLY A DESIGNATED LIMITED THREAT OF
FLOODING BY THE NATIONAL WATER CENTER ACROSS PARTS OF THE EAST AND GULF COASTS
FOR WEEK-1, THUS HEAVY RAINFALL COULD SUPPORT LOCALIZED FLOODING. THE ECENS PET
AND UNCALIBRATED ENSEMBLE OUTPUT IS MORE FAVORABLE OF HEAVY RAINFALL OCCURRING
OVER LAND COMPARED TO THE GEFS, INDICATING AT LEAST A 20% CHANCE OF 3-DAY
RAINFALL EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY AND ONE INCH.
ACROSS THE WEST, THE PATTERN AND MODEL GUIDANCE IS LESS FAVORABLE FOR HIGH
WINDS ACROSS SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA, THUS THIS HAZARD HAS
BEEN DISCONTINUED IN TODAY'S OUTLOOK.
FORECASTER: MELISSA OU
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