869
FXUS21 KWNC 041819
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 04 2025
SYNOPSIS: AT THE OUTSET OF WEEK-2, MID-LEVEL HIGH PRESSURE IS FORECAST ACROSS
CENTRAL NORTH AMERICA FAVORING A PATTERN CHANGE WITH ABOVE-NORMAL TEMPERATURES
RETURNING ACROSS PORTIONS OF THE GREAT PLAINS AND MIDWEST. DYNAMICAL MODELS
HAVE CONTINUED TO TREND WARMER, WITH EXTREME HEAT CONCERNS POTENTIALLY EMERGING
OVER PORTIONS OF THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. MID-LEVEL LOW
PRESSURE IS FORECAST OVER THE WESTERN THIRD OF THE CONUS EARLY IN THE PERIOD
FAVORING ENHANCED WIND SPEEDS OVER PARTS OF THE SOUTHWEST AND EXTENDING THROUGH
THE GREAT PLAINS. A STALLED FRONTAL BOUNDARY REMAINS FORECAST ALONG THE EAST
COAST AND EASTERN GULF OF AMERICA RESULTING IN INCREASED LIKELIHOOD FOR
ENHANCED PRECIPITATION AND HIGH WINDS. SURFACE LOW PRESSURE IS FORECAST TO
BRING INCREASED CHANCES OF HEAVY PRECIPITATION AND ELEVATED WIND SPEEDS TO
SOUTHERN AND SOUTHEASTERN COASTAL ALASKA.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS THE FLORIDA PENINSULA AND COASTAL
SOUTHEAST, FRI-SUN, SEP 12-14.
SLIGHT RISK OF HIGH WINDS ACROSS FLORIDA, THE EASTERN GULF COAST, AND PORTIONS
OF THE MID-ATLANTIC AND SOUTHEAST COASTS, FRI-SUN, SEP 12-14.
SLIGHT RISK OF HIGH WINDS OVER PARTS OF THE SOUTHWESTERN U.S. INTO THE CENTRAL
AND SOUTHERN ROCKIES AND PLAINS, FRI-SAT, SEP 12-13.
SLIGHT RISK OF EXTREME HEAT ACROSS PORTIONS OF THE CENTRAL PLAINS, MIDDLE
MISSISSIPPI VALLEY, AND OHIO VALLEY, FRI-TUE, SEP 12-16.
SLIGHT RISK OF HIGH WINDS ACROSS COASTAL PORTIONS OF SOUTHERN AND SOUTHEASTERN
ALASKA, FRI-TUE, SEP 12-16.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE LOWER MISSISSIPPI AND TENNESSEE
VALLEYS.
DETAILED SUMMARY
FOR SUNDAY SEPTEMBER 07 - THURSDAY SEPTEMBER 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY SEPTEMBER 12 - THURSDAY SEPTEMBER 18: RIDGING AND ASSOCIATED
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST TO EXPAND ACROSS THE
NORTH-CENTRAL U.S. EARLY IN WEEK-2 FAVORING ABOVE-NORMAL TEMPERATURES OVER MUCH
OF THE CENTRAL CONUS. THE ECENS PROBABILISTIC EXTREME TOOL (PET) DEPICTS A
STRONGER SIGNAL FOR HAZARDOUS HEAT COMPARED TO YESTERDAY, WITH AT LEAST A 20
PERCENT CHANCE TEMPERATURES EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 90
DEG F EXTENDING AS FAR NORTH AS THE MIDDLE MISSISSIPPI AND OHIO VALLEYS. THE
GEFS PET IS BROADER IN COVERAGE AND HAS HIGHER PROBABILITIES (GREATER THAN 40
PERCENT), WITH SOME AREAS HAVING THE POTENTIAL TO EXCEED 95 DEG F. BY THE END
OF WEEK-2, THE 0Z ECENS, GEFS, AND CMCE ALL DEPICT A BROADLY AMPLIFIED RIDGE
ACROSS CENTRAL CANADA WITH A LOWER AMPLITUDE PATTERN DEVELOPING OVER THE CONUS
WHICH MAY PERSIST THE WARM PATTERN. GIVEN THESE INCREASED SIGNALS, A SLIGHT
RISK OF EXTREME HEAT IS HIGHLIGHTED ACROSS PORTIONS OF THE CENTRAL PLAINS,
MIDDLE MISSISSIPPI VALLEY, AND OHIO VALLEY, SEP 12-16. FOR MANY OF THESE AREAS,
THIS WOULD MARK A QUICK RETURN OF SUMMER-LIKE HEAT FOLLOWING TEMPERATURES MORE
TYPICAL OF EARLY FALL DURING WEEK-1. THE HEAT RISK IS NOT EXTENDED SOUTH DUE TO
HIGHER HEAT THRESHOLDS. HOWEVER, A RAPID ONSET DROUGHT (ROD) RISK IS POSTED
OVER PORTIONS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS DUE TO 60-DAY
PRECIPITATION DEFICITS REGISTERING UPWARDS OF 4-INCHES WITH VERY DRY CONDITIONS
FORECAST DURING THE NEXT 2 WEEKS.
UPSTREAM OF THE AFOREMENTIONED RIDGE, TROUGHING IS PREDICTED OVER THE WESTERN
CONUS, WITH THIS FEATURE GRADUALLY WEAKENING GOING INTO WEEK-2. THIS FEATURE IS
LIKELY TO LEAD TO SOME ENHANCEMENT OF PRECIPITATION, PARTICULARLY ACROSS THE
NORTHWEST WHERE THE ECENS PET DEPICTS HIGH PROBABILITIES (GREATER THAN 60
PERCENT) FOR 3-DAY PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE.
HOWEVER, PROBABILITIES IN THE GEFS PET ARE MUCH LOWER (20-30 PERCENT), AND
ACTUAL 24-HOUR PRECIPITATION AMOUNTS ARE FORECAST TO BE UNDER A HALF-INCH IN
THE UNCALIBRATED VERSIONS OF BOTH MODELS. HIGHER PROBABILITIES IN THE PETS ARE
LIKELY TIED TO THE LOWER PRECIPITATION CLIMATOLOGY THIS TIME OF YEAR. WHILE
UNSETTLED WEATHER IS POSSIBLE ACROSS THE NORTHWEST IN ASSOCIATION WITH THE
TROUGH, HAZARDOUS CONDITIONS ARE NOT EXPECTED, PRECLUDING A RELATED
PRECIPITATION HAZARD. HOWEVER, THE TROUGH MAY LEAD TO ELEVATED WIND SPEEDS OVER
PARTS OF THE SOUTHWESTERN U.S. INTO THE GREAT PLAINS. A SLIGHT RISK OF HIGH
WINDS IS POSTED OVER PORTIONS OF THE CALIFORNIA COAST, GREAT BASIN, SOUTHWEST,
AND THE CENTRAL AND SOUTHERN ROCKIES AND PLAINS, SEP 12-13, COINCIDING WITH THE
STRONGEST SIGNAL IN THE ECENS PET. WILDFIRE DEVELOPMENT AND SPREAD IS THE
PRIMARY CONCERN ACROSS THE WEST DUE TO SOIL MOISTURE VALUES IN THE LOWEST 10TH
CLIMATOLOGICAL PERCENTILE. THE WIND THREAT IS FORECAST TO SUBSIDE BY THE MIDDLE
OF WEEK-2 AS THE TROUGHING WEAKENS.
A STALLED FRONTAL BOUNDARY REMAINS FORECAST JUST OFF THE EAST COAST OF THE
CONUS AND INTO THE EASTERN GULF OF AMERICA SERVING AS A FOCUS FOR ENHANCED
PRECIPITATION. COMPARED TO YESTERDAY, THE 0Z ECENS AND GEFS AND THEIR
CORRESPONDING PETS DEPICT THE HEAVIEST PRECIPITATION FURTHER TO THE SOUTH AND
EAST, PARTICULARLY ACROSS THE FLORIDA PENINSULA AND THE COASTAL SOUTHEAST WHERE
A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS DESIGNATED, SEP 12-14. SURFACE
HIGH PRESSURE ACROSS THE NORTHEAST FAVORS ENHANCED EASTERLY FLOW ALONG PARTS OF
THE EASTERN SEABOARD, WITH THE ECENS PET DEPICTING A 20 PERCENT CHANCE OF WIND
SPEEDS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 25-MPH. THE SLIGHT WIND
RISK INCLUDES PORTIONS OF THE COASTAL MID-ATLANTIC AND SOUTHEAST, AS WELL AS
THE NORTHEASTERN GULF COAST, SEP 12-14. IT IS NOT OUT OF THE QUESTION TO HAVE
AN AREA OF SURFACE LOW PRESSURE SPIN UP ALONG THE FRONTAL BOUNDARY OFF THE EAST
COAST DURING WEEK-2, WHICH COULD EXACERBATE IMPACTS ALONG THE COAST. THE
NATIONAL HURRICANE CENTER CONTINUES TO INDICATE A TROPICAL DISTURBANCE (INVEST
91L) ACROSS THE ATLANTIC MAIN DEVELOPMENT REGION WITH HIGH CHANCES FOR TROPICAL
CYCLONE FORMATION IN THE NEXT WEEK. THERE HAS BEEN A TREND TOWARD MORE WESTWARD
TRACKS IN RECENT DETERMINISTIC RUNS OF THE GFS AND ECMWF AS WELL AS SOME
INDIVIDUAL ENSEMBLE MEMBERS. WHILE IT IS FAR TOO EARLY TO DETERMINE IF ANY
IMPACTS WILL OCCUR, THIS SYSTEM WILL NEED TO BE MONITORED GIVEN ITS POTENTIAL
TO APPROACH THE U.S. LATER IN WEEK-2.
MID-LEVEL TROUGHING AND ASSOCIATED SURFACE LOW PRESSURE ACROSS THE BERING SEA
AND INTO THE GULF OF ALASKA ARE FORECAST TO BRING PERIODS OF INTERMITTENT HEAVY
PRECIPITATION AND HIGH WINDS TO SOUTH-CENTRAL AND SOUTHEASTERN COASTAL ALASKA
DURING WEEK-2. THE ECENS PET DEPICTS AT LEAST A 20 PERCENT CHANCE OF WIND
SPEEDS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 40-MPH ACROSS SOUTHERN
AND SOUTHEASTERN COASTAL ALASKA DURING THE EARLY AND MIDDLE PARTS OF THE
PERIOD. THEREFORE, A SLIGHT RISK IS HIGHLIGHTED FOR HIGH WINDS ACROSS THIS
AREA, SEP 12-16. AN ASSOCIATED HEAVY PRECIPITATION HAZARD IS NOT ISSUED AT THIS
TIME GIVEN THE UNCERTAINTY OF WHETHER TOTALS WOULD REACH HAZARDOUS CRITERIA
OVER A WIDESPREAD AREA.
FORECASTER: THOMAS COLLOW
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