401
FXUS21 KWNC 281815
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 28 2026
SYNOPSIS: BROAD MID-LEVEL RIDGING IS FORECAST TO PERSIST ACROSS THE
SOUTHEASTERN AND SOUTH-CENTRAL CONTIGUOUS U.S. (CONUS) 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. MID-LEVEL LOW
PRESSURE FORECAST ACROSS THE NORTHWESTERN CONUS EARLY IN THE PERIOD FAVORS
EARLY SEASON FROSTS OR FREEZES, PARTICULARLY ACROSS HIGHER ELEVATIONS. 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,
MIDDLE AND LOWER MISSISSIPPI VALLEY, WESTERN PORTIONS OF THE TENNESSEE AND OHIO
VALLEYS, AND THE SOUTHEAST, SAT-SUN, SEP 5-6.
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE GREAT PLAINS, MISSISSIPPI, OHIO,
AND TENNESSEE VALLEYS, SOUTHEAST, AND MID-ATLANTIC, SAT-WED, SEP 5-9.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN GREAT
BASIN, NORTHERN ROCKIES, AND NORTHERN HIGH PLAINS, SAT-SUN, SEP 5-6.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS
AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR MONDAY AUGUST 31 - FRIDAY SEPTEMBER 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY SEPTEMBER 05 - FRIDAY SEPTEMBER 11: THE 0Z ECMWF, GEFS, AND
CANADIAN ENSEMBLES ARE IN GOOD AGREEMENT REGARDING MID-LEVEL RIDGING ACROSS THE
SOUTH-CENTRAL AND SOUTHEASTERN CONUS AT THE START OF WEEK-2. HOWEVER, THE
MODELS INDICATE A DECREASE IN AMPLITUDE OF THIS FEATURE COMPARED TO WEEK-1 AND
AN OVERALL FLATTENING OF THE RIDGE AS IT RETROGRADES SLIGHTLY. THIS EVOLUTION
SUPPORTS A CONTINUATION OF ANOMALOUSLY WARM TEMPERATURES (UPWARDS OF +10 DEG F
ABOVE NORMAL) CONTINUING ACROSS THE CENTRAL AND SOUTHERN PLAINS AND ADJACENT
AREAS OF THE MISSISSIPPI VALLEY INTO LABOR DAY WEEKEND. THE GEFS AND ECMWF
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT AT LEAST A 40 PERCENT CHANCE OF
MAXIMUM TEMPERATURES EXCEEDING THE 90TH CLIMATOLOGICAL PERCENTILE EARLY IN THE
PERIOD, WITH A VERY STRONG SIGNAL ALSO BEING DEPICTED IN THE GEFS-ECMWF
SKILL-WEIGHTED CALIBRATED HEAT RISK GUIDANCE. 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. AS A RESULT, THE MODERATE RISK FOR EXTREME HEAT REMAINS POSTED
SEP 5-6 ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS, MIDDLE AND LOWER
MISSISSIPPI VALLEY, WESTERN PORTIONS OF THE TENNESSEE AND OHIO VALLEYS, AND THE
SOUTHEAST. THE SLIGHT RISK CONTINUES THROUGH SEP 9 AND EXTENDS THROUGHOUT MUCH
OF THE MIDWEST, AND ALSO INTO THE SOUTHEAST AND MID-ATLANTIC. THE SLIGHT RISK
IS REMOVED FROM MOST OF THE FLORIDA PENINSULA DUE TO WEAKER SIGNALS IN THE HEAT
RISK GUIDANCE AS WELL AS THE POTENTIAL FOR AN INFLUX OF TROPICAL MOISTURE TIED
TO THE REMNANTS OF TROPICAL STORM DOLLY WHICH MAY REDUCE TEMPERATURES. 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.
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.
AMPLIFIED RIDGING FORECAST ACROSS THE GULF OF ALASKA RESULTS IN DOWNSTREAM
TROUGHING DEVELOPING OVER THE NORTHWESTERN CONUS. THIS FAVORS ENHANCED ONSHORE
FLOW AND MOISTURE ADVECTION LEADING TO ABOVE-NORMAL PRECIPITATION OVER MUCH OF
THE WEST. THE ECMWF AND CANADIAN ENSEMBLES ARE QUICKER TO WEAKEN THIS FEATURE
EARLY IN WEEK-2 COMPARED TO THE GEFS, WITH A FASTER RETROGRESSION OF THE
UPSTREAM RIDGE LEADING TO RISING HEIGHTS OVER THE WEST BY DAY-10. WHILE
PRECIPITATION AMOUNTS ARE UNLIKELY TO REACH HAZARDS THRESHOLDS, COLD AIR
ADVECTION IS FORECAST ACROSS PORTIONS OF THE NORTHWEST, WITH BOTH ECMWF AND
GEFS ENSEMBLES SHOWING INCREASED CHANCES FOR NIGHTTIME MINIMUM TEMPERATURES
FALLING BELOW 40 DEG F (32 DEG F IN THE HIGHER ELEVATIONS) SUPPORTIVE OF THE
FIRST FROST AND/OR FREEZES. IN ADDITION, BOTH GEFS AND ECMWF PETS ARE IN
AGREEMENT INDICATING AT LEAST 20 PERCENT CHANCES OF THESE TEMPERATURES FALLING
BELOW THE 15TH CLIMATOLOGICAL PERCENTILE OVER SOME AREAS, THUS A SLIGHT RISK OF
MUCH BELOW NORMAL TEMPERATURES IS POSTED FOR PARTS OF THE NORTHERN GREAT BASIN,
NORTHERN ROCKIES, AND NORTHERN HIGH PLAINS FOR SEP 5-6. EVEN IF ANY FROST
AND/OR FREEZES DO NOT OCCUR, THE PROSPECT OF ANOMALOUSLY COLD AIR IS EXPECTED
TO ALLEVIATE FIRE WEATHER CONDITIONS, AS THIS PART OF THE COUNTRY HAS BEEN
EMBATTLED BY AMPLE WILDFIRE ACTIVITY THIS SUMMER.
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 135 DEG W AND 115 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 U.S. BY THE START OF
WEEK-2. HOWEVER, THE ECMWF ENSEMBLES DEPICT ANOTHER SYSTEM POTENTIALLY
DEVELOPING OFFSHORE MEXICO WITH A SIMILAR TRACK. WHILE THE SLIGHT RISK OF HEAVY
PRECIPITATION IS DISCONTINUED OVER THE DESERT SOUTHWEST IN TODAY'S OUTLOOK,
THIS POTENTIAL THIRD SYSTEM 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 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.
ACROSS THE ATLANTIC, TROPICAL STORM DOLLY HAS OPENED UP INTO A WAVE. THERE IS
SOME POTENTIAL FOR REGENERATION IF THE REMNANTS OF THIS SYSTEM MAKE IT INTO THE
WESTERN ATLANTIC WHERE THERE IS NOTABLY LESS WIND SHEAR. THE TIMING AND EXACT
LOCATION ARE UNCERTAIN, BUT SOME INDIVIDUAL GEFS AND ECMWF ENSEMBLE MEMBERS
DEPICT LOW PRESSURE CLOSE TO THE SOUTHEASTERN U.S. COAST EARLY IN WEEK-2 WHICH
COULD HAVE SOME IMPLICATIONS FOR THE EXTENDED 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: THOMAS COLLOW
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