335
FXUS21 KWNC 301823
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 30 2026
SYNOPSIS: BROAD MID-LEVEL RIDGING IS FORECAST TO LINGER ACROSS THE
SOUTH-CENTRAL CONTIGUOUS U.S. (CONUS) FROM THE END OF WEEK-1 INTO WEEK-2
FAVORING A CONTINUATION OF ANOMALOUS WARMTH AND EXTREME HEAT CENTERED ACROSS
THE CENTRAL AND SOUTHERN PLAINS INTO THE MIDDLE AND LOWER MISSISSIPPI VALLEY.
THE ABNORMALLY HOT AND DRY CONDITIONS OVER THE PAST FEW WEEKS ARE EXPECTED TO
CONTINUE THROUGH MUCH OF WEEK-2, SUPPORTING A RAPID ONSET DROUGHT (ROD) RISK
FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS AND THE MIDDLE AND LOWER
MISSISSIPPI VALLEY.
HAZARDS
MODERATE RISK OF EXTREME HEAT FOR PARTS OF THE CENTRAL AND SOUTHERN PLAINS, AND
MIDDLE AND LOWER MISSISSIPPI VALLEY, MON-TUE, SEP 7-8.
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE DESERT SOUTHWEST, CENTRAL AND
EAST-CENTRAL CONUS, MON-THU, SEP 7-10.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS
AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR WEDNESDAY SEPTEMBER 02 - SUNDAY SEPTEMBER 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR MONDAY SEPTEMBER 07 - SUNDAY SEPTEMBER 13: THE 0Z ECMWF, GEFS, AND CANADIAN
ENSEMBLES INDICATE MID-LEVEL RIDGING LINGERING ACROSS THE SOUTH-CENTRAL CONUS
AT THE START OF WEEK-2, WITH THE ECMWF ENSEMBLE CONTINUING TO BE THE MOST
PRONOUNCED RELATIVE TO THE GEFS AND CMCE, DEPICTING A 595-DM HIGH CENTERED
OVER THE EASTERN FOUR CORNERS AT THE START OF THE PERIOD. THIS PATTERN SUPPORTS
A CONTINUATION OF ANOMALOUSLY WARM TEMPERATURES (UPWARDS OF +10 DEG F ABOVE
NORMAL) ACROSS THE CENTRAL AND SOUTHERN PLAINS AND ADJACENT AREAS OF THE
MISSISSIPPI VALLEY. A MODERATE RISK (40-60% CHANCE) OF EXTREME HEAT IS
DESIGNATED FOR THESE AREAS WHERE THE GEFS AND ECMWF PROBABILISTIC EXTREMES
TOOLS (PETS) CONTINUE TO INDICATE AT LEAST A 40% CHANCE OF MAXIMUM TEMPERATURES
EXCEEDING THE 90TH PERCENTILE CLIMATOLOGICALLY. THERE HAS BEEN A DECREASE IN
HEAT SIGNAL COMPARED TO YESTERDAY IN THE PETS, WITH PROBABILITIES OF EXCEEDING
THIS THRESHOLD ACROSS THE CENTRAL CONUS LIMITED TO 40-50% CHANCES, WHEREAS
YESTERDAY'S GUIDANCE CONTINUED TO SHOW AREAS GREATER THAN 50%. THEREFORE THE
SPATIAL COVERAGE OF THE MODERATE RISK AREA HAS DECREASED COMPARED TO YESTERDAY.
ACTUAL TEMPERATURES IN THE UPPER 90S DEG F TO 100S DEG F ARE LIKELY WITH HEAT
INDEX VALUES NEAR 110 DEG F IN THE MORE HUMID AREAS OF EASTERN TEXAS AND THE
LOWER MISSISSIPPI VALLEY AND 105 DEG F FARTHER NORTH. THE SLIGHT RISK (20-40%
CHANCE) CONTINUES THROUGH SEP 10 AND EXTENDS THROUGHOUT MUCH OF THE MIDWEST,
AND ALSO INTO THE SOUTHEAST. PARTS OF THE SOUTHWESTERN CONUS HAVE BEEN REMOVED
FROM THE SLIGHT RISK WITH THE RISK BEING LIMITED TO THE DESERT SOUTHWEST. WHILE
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST THROUGHOUT THE PERIOD, THE
DECLINING TEMPERATURE CLIMATOLOGY AND SHORTENING DAYLIGHT HOURS REDUCE
CONFIDENCE REGARDING EXTREME HEAT HEADING INTO MID-SEPTEMBER. ADDITIONALLY, BY
MID WEEK-2 THERE IS SIGNIFICANT UNCERTAINTY ABOUT THE EVOLUTION OF THE
MID-LEVEL RIDGE TRANSLATING TO UNCERTAINTY REGARDING TEMPERATURE HAZARDS AND
HAZARDS IN GENERAL.
THE CONTINUED EXTREME HEAT RISKS DURING WEEK-2 ARE LIKELY BEING REINFORCED BY
FEEDBACK PROCESSES ASSOCIATED WITH RAPIDLY DRYING SOILS AND DROUGHT WITHIN MANY
OF THE HIGHLIGHTED REGIONS. THE HOT AND DRY CONDITIONS FAVORED ARE ALSO
EXPECTED TO ELEVATE THE RISK OF FIRE WEATHER CONDITIONS DURING THE PERIOD. IN
ADDITION, A RAPID ONSET DROUGHT (ROD) RISK IS DESIGNATED ACROSS PORTIONS OF THE
CENTRAL AND SOUTHERN PLAINS AND MIDDLE AND LOWER MISSISSIPPI VALLEY. THIS AREA
HAS REGISTERED 30- TO 45-DAY PRECIPITATION DEFICITS GREATER THAN 2 INCHES BELOW
NORMAL AND/OR UNDER HALF OF NORMAL, WITH LESS THAN AN INCH EXPECTED DURING THE
NEXT TWO WEEKS. THE NATIONAL HURRICANE CENTER IS MONITORING A DISTURBANCE IN
THE GULF THAT MAY BRING PRECIPITATION TO PORTIONS OF THE GULF COAST. THIS MAY
WARRANT ADJUSTING THE ROD RISK TOMORROW IF TRENDS CONTINUE.
AMPLIFIED RIDGING FORECAST ACROSS THE GULF OF ALASKA RESULTS IN DOWNSTREAM
TROUGHING DEVELOPING OVER THE NORTHWESTERN CONUS LATE IN WEEK-1. THE MORE
AMPLIFIED TROUGHING ACROSS THE NORTHWEST IS ANTICIPATED TO TIME OUT DURING
WEEK-1, WITH INCREASED UNCERTAINTY ABOUT THE AMPLITUDE OF THIS FEATURE BY
WEEK-2. WITH DECREASING SIGNALS OF FROSTS OR FREEZES TIMING OUT BY WEEK-2, THE
MUCH BELOW NORMAL TEMPERATURE HAZARD HAS BEEN DISCONTINUED IN TODAY'S OUTLOOK.
ACROSS THE EASTERN AND CENTRAL PACIFIC, THERE HAS BEEN A PRONOUNCED UPTICK IN
TROPICAL ACTIVITY DURING THE PAST WEEK. TROPICAL STORMS KARINA AND LOWELL ARE
LOCATED NEAR 120 DEG W AND 140 DEG W RESPECTIVELY. THE NATIONAL HURRICANE
CENTER (NHC) FORECASTS KARINA TO STRENGTHEN INTO A MAJOR HURRICANE AS IT TRACKS
WEST-NORTHWESTWARD. KARINA ALONG WITH A POTENTIAL ADDITIONAL AREA HIGHLIGHTED
WITH A HIGH CHANCE FOR TROPICAL CYCLONE DEVELOPMENT IN THE SAME AREA MAY LEAD
TO ENHANCED MOISTURE ADVECTION ACROSS THE SOUTHWESTERN U.S. BOTH OF THESE
SYSTEMS ARE FORECAST TO BE MOVING FARTHER AWAY FROM THE WEST COAST OF NORTH
AMERICA TOWARDS HAWAII BY THE START OF WEEK-2. HOWEVER, THE ECMWF ENSEMBLES
DEPICT ANOTHER SYSTEM POTENTIALLY DEVELOPING OFFSHORE MEXICO WITH A SIMILAR
TRACK WHICH WILL NEED TO BE MONITORED AS IT COULD TRIGGER A RENEWED GULF SURGE
EVENT IN MID TO LATE WEEK-2.
TROPICAL STORM LOWELL IS FORECAST TO STRENGTHEN INTO A HURRICANE AS IT MOVES
WESTWARD ACROSS THE PACIFIC. THIS SYSTEM WILL NEED TO BE MONITORED AS SOME GEFS
AND ECMWF ENSEMBLE MEMBERS TURN THE SYSTEM MORE NORTH TOWARD THE HAWAIIAN
ISLANDS EARLY IN WEEK-2. ALTHOUGH THERE IS AMPLE UNCERTAINTY ASSOCIATED WITH
THIS DISTURBANCE, HEAVY PRECIPITATION, HIGH WINDS, AND OTHER ADVERSE IMPACTS TO
HAWAII CANNOT BE RULED OUT DURING WEEK-2, WITH BOTH THE GEFS AND ECMWF PETS
DEPICTING AT LEAST A 20 PERCENT CHANCE OF 3-DAY PRECIPITATION VALUES EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE ACROSS THE STATE.
IN THE ATLANTIC, TROPICAL STORM DOLLY HAS OPENED UP INTO A WAVE. THERE IS SOME
POTENTIAL FOR SOME REDEVELOPMENT BY THE MIDDLE OF THIS WEEK AS THE SYSTEM
REACHES THE SOUTHEASTERN GULF OF AMERICA. WHILE UNLIKELY TO BE A SIGNIFICANT
SYSTEM, THERE COULD BE PERIODS OF LOCAL ENHANCED RAINFALL ACROSS PARTS OF
FLORIDA AND THE SOUTHEAST LINGERING FROM THE END OF WEEK-1 INTO THE START OF
WEEK-2, ALTHOUGH MUCH OF IT SEEMS TO LIKELY TIME OUT PRIOR TO THIS PERIOD.
THEREFORE THE SLIGHT RISK OF HEAVY PRECIPITATION IS DISCONTINUED IN TODAY'S
OUTLOOK.
ENHANCED ONSHORE FLOW MAY BRING PERIODS OF HEAVY PRECIPITATION AND GUSTY WINDS
ACROSS SOUTHERN ALASKA LATE IN WEEK-1 INTO THE START OF WEEK-2, ALTHOUGH TOOLS
DO NOT INDICATE HAZARDS THRESHOLDS BEING REACHED. SNOW CANNOT BE RULED OUT
ACROSS PORTIONS OF THE BROOKS RANGE AND THE HIGHER ELEVATIONS OF SOUTHEASTERN
ALASKA.
FORECASTER: MELISSA OU
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page