539
FXUS21 KWNC 161826
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 16 2025
SYNOPSIS: MID-LEVEL HIGH PRESSURE ACROSS MUCH OF THE WESTERN CONTIGUOUS U.S.
(CONUS) MAY BRING A BRIEF SHOT OF EXTREME HEAT TO THE DESERT SOUTHWEST AT THE
BEGINNING OF WEEK-2. MID-LEVEL LOW PRESSURE IS ANTICIPATED TO QUICKLY FOLLOW
BEHIND, SHIFTING EASTWARD, POTENTIALLY BRINGING THE FIRST HEAVY SNOW OF THE
SEASON TO NORTHERN PORTIONS OF THE ROCKIES. MEANWHILE, SURFACE HIGH PRESSURE
OVER THE NORTH PACIFIC ADJACENT TO SURFACE LOW PRESSURE OVER THE WESTERN CONUS
COULD BRING PERIODS OF HIGH WINDS TO COASTAL PORTIONS OF THE WEST COAST FROM
THE BEGINNING TO MIDDLE OF WEEK-2. RAPID ONSET DROUGHT REMAINS A RISK FOR PARTS
OF THE SOUTHEAST WHERE ABOVE-NORMAL TEMPERATURES AND LIMITED WEEK-1
PRECIPITATION ARE FORECAST.
HAZARDS
SLIGHT RISK OF EXTREME HEAT FOR THE DESERT SOUTHWEST, WED-THU, SEP 24-25.
SLIGHT RISK OF HEAVY SNOW ACROSS PARTS OF THE NORTHERN AND NORTHERN CENTRAL
ROCKIES, FRI-SUN, SEP 26-28.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR COASTAL PORTIONS OF THE WEST COAST,
WED-SUN, SEP 24-28.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF MISSISSIPPI, ALABAMA, AND
GEORGIA.
DETAILED SUMMARY
FOR FRIDAY SEPTEMBER 19 - TUESDAY SEPTEMBER 23:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY SEPTEMBER 24 - TUESDAY SEPTEMBER 30: AT THE BEGINNING OF WEEK-2,
AMPLIFIED MID-LEVEL RIDGING IS ANTICIPATED TO BUILD ACROSS MUCH OF THE WESTERN
TWO-THIRDS OF THE CONUS, WITH UPSTREAM MID-LEVEL TROUGHING OVER THE NORTHEAST
PACIFIC. THIS RIDGE IS FAIRLY SHORT-LIVED WITH THE PATTERN SHIFTING EASTWARD
RESULTING IN A TRANSITION TO MID-LEVEL TROUGHING ACROSS THE NORTHWEST AND
RIDGING OVER THE EASTERN CONUS BY THE LATTER PART OF THE PERIOD.
AMPLIFIED MID-LEVEL RIDGING IS ANTICIPATED TO BUILD ACROSS MUCH OF THE WEST
EXCLUDING THE PACIFIC NORTHWEST AT THE BEGINNING OF THE PERIOD. MULTIPLE
PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE AT LEAST A 20% CHANCE OF MAXIMUM
TEMPERATURES EXCEEDING THE 90TH PERCENTILE CLIMATOLOGICALLY AND 105 DEG F,
FURTHER SUPPORTED BY OTHER GUIDANCE TOOLS SHOWING INCREASING SIGNALS FOR
EXTREME HEAT. ADDITIONALLY, ENHANCED DEWPOINT TEMPERATURES COULD RESULT IN
HIGHER HEAT INDEX VALUES. THEREFORE A SLIGHT RISK (20-40% CHANCE) OF EXTREME
HEAT IS POSTED FOR PARTS OF THE DESERT SOUTHWEST, SEP 24-25. THIS HEAT FEATURE
IS LIKELY TO BE FAIRLY SHORT-LIVED DUE TO AN ANTICIPATED PROGRESSIVE PATTERN.
UPSTREAM, AMPLIFIED MID-LEVEL TROUGHING IS ANTICIPATED TO FORM OVER THE
NORTHEASTERN PACIFIC AND SHIFT EASTWARD INTO THE WESTERN CONUS THROUGHOUT THE
BEGINNING OF WEEK-2. THIS PATTERN IN ADDITION TO PREDICTED SURFACE HIGH
PRESSURE NEAR THE WEST COAST AND ADJACENT SURFACE LOW PRESSURE OVER WEST COAST
STATES MAY RESULT IN A TIGHT PRESSURE GRADIENT AT THE SURFACE AND INCREASED
LIKELIHOOD FOR HIGH WINDS ACROSS THE WEST COAST. A SLIGHT RISK OF EPISODIC HIGH
WINDS IS HIGHLIGHTED FOR COASTAL PORTIONS OF THE WEST COAST FOR SEP 24-28,
WHERE PETS INDICATE AT LEAST A 20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE AND 25 MPH. AS THIS TROUGH SHIFTS EASTWARD, IT MAY BE ACCOMPANIED BY
AN INCREASED LIKELIHOOD OF HEAVY SNOW ACROSS HIGH ELEVATION AREAS OF THE
ROCKIES. A SLIGHT RISK OF HEAVY SNOW IS HIGHLIGHTED FOR PARTS OF THE NORTHERN
AND NORTHERN CENTRAL ROCKIES, SEP 26-28. THE GEFS PET SHOWS AT LEAST A 20%
CHANCE OF 3-DAY ACCUMULATIONS EXCEEDING THE 85TH PERCENTILE. UNCALIBRATED
ENSEMBLES INDICATE AT LEAST A 20% CHANCE OF SOME LOCALIZED AREAS EXCEEDING 4
INCHES. THIS WOULD BE ONE OF THE FIRST SIGNIFICANT SNOWS OF THE SEASON FOR THIS
REGION.
THE NATIONAL HURRICANE CENTER (NHC) IS MONITORING A DISTURBANCE FOR POTENTIAL
DEVELOPMENT OFF THE SOUTHWEST COAST OF MEXICO. THE TRACK OF THIS SYSTEM MAY
BRING IT TOWARDS THE GULF OF CALIFORNIA AND POTENTIALLY TOUCH OFF ANOTHER GULF
SURGE EVENT IN THE SOUTHWEST. HOWEVER, MODEL GUIDANCE CONTINUES TO HAVE A WEAK
SIGNAL REGARDING HAZARDOUS PRECIPITATION RESULTING IN NO PRECIPITATION HAZARD
FORECAST IN THE SOUTHWEST. OVER THE ATLANTIC, AS OF 8AM EDT, THE NHC INDICATES
AN AREA OVER THE CENTRAL ATLANTIC WITH A 90% CHANCE OF TROPICAL CYCLONE
FORMATION IN THE NEXT 7 DAYS. THE CPC WEEK-2 GLOBAL TROPICAL HAZARDS OUTLOOK
SHOWS A 20-40% CHANCE OF TROPICAL CYCLONE DEVELOPMENT IN THE SOUTHWESTERN GULF
OF AMERICA. THERE IS SOME INDICATION THAT THIS COULD SUPPORT AN EXTENSION OF
ENHANCED MOISTURE INTO THE GULF COAST, ALTHOUGH THERE IS TOO MUCH UNCERTAINTY
AT THIS TIME TO DESIGNATE AN ASSOCIATED PRECIPITATION HAZARD. THIS AREA WILL BE
MONITORED CLOSELY IN THE UPCOMING DAYS.
A STALLED FRONTAL BOUNDARY IS FORECAST ALONG THE SOUTHEAST COAST AND ACROSS
FLORIDA DURING THE WEEK-1 PERIOD. THE WEATHER PREDICTION CENTER (WPC) IS
FORECASTING UP TO 4 INCHES OF RAIN ACROSS SOUTH FLORIDA DURING WEEK-1. THE
NATIONAL WATER CENTER (NWC) IS MONITORING THE POTENTIAL FOR FLOODING TO OCCUR
DURING WEEK-1 ACROSS THIS AREA. DUE TO DECREASED POTENTIAL FOR ENHANCED
RAINFALL DURING WEEK-2 THIS POSSIBLE FLOOD HAZARD IS NOT DESIGNATED FOR THE
PERIOD.
ABOVE NORMAL PRECIPITATION CONTINUES TO BE FORECAST FOR THE NORTHWEST
ASSOCIATED WITH THE MID-LEVEL TROUGH PROGRESSING INTO THE REGION. MEAN
PRECIPITATION AMOUNTS FORECAST BY THE GEFS AND ECENS ARE AROUND 1 INCH.
THEREFORE, WHILE THESE AMOUNTS ARE ABOVE NORMAL FOR THIS TIME OF YEAR,
HAZARDOUS THRESHOLDS ARE NOT LIKELY TO BE EXCEEDED.
THERE CONTINUES TO BE AN INCREASED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES
ACROSS MUCH OF THE CONUS. THE COMBINATION OF ABOVE-NORMAL TEMPERATURES, 30 TO
60-DAY PRECIPITATION DEFICITS, AND LIMITED PRECIPITATION FORECAST DURING THE
NEXT WEEK SUPPORTS A RAPID ONSET DROUGHT (ROD) RISK ACROSS MISSISSIPPI,
ALABAMA, AND GEORGIA. DRY VEGETATIVE FUELS IN THIS AREA TYPICALLY MEANS
INCREASED RISK OF WILDFIRES. THERE ARE SOME INDICATIONS THAT A WEAKNESS IN THE
SUBTROPICAL RIDGE MAY BEGIN TO BRING MORE PRECIPITATION TO THE REGION BY
WEEK-2. HOWEVER, THE CHANCES FOR ABOVE-NORMAL PRECIPITATION ARE QUITE LOW AT
THIS TIME BUT WILL BE MONITORED GOING FORWARD.
FORECASTER: MELISSA OU
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