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FXUS21 KWNC 271837
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 27 2026
SYNOPSIS: TODAY'S MODELS ARE IN BETTER AGREEMENT COMPARED TO YESTERDAY
REGARDING MID-LEVEL RIDGING PERSISTING ACROSS THE SOUTH-CENTRAL CONUS AT LEAST
INTO THE LABOR DAY WEEKEND. THIS FAVORS A CONTINUATION OF A STRETCH 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. ENHANCED MOISTURE
ADVECTION FAVORED OVER THE SOUTHWESTERN CONUS INCREASES CHANCES FOR HEAVY
PRECIPITATION ACROSS PARTS OF THE DESERT SOUTHWEST. 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 LOWER AND MIDDLE 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, FRI-SUN, SEP 4-6.
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE GREAT PLAINS, MISSISSIPPI, OHIO,
AND TENNESSEE VALLEYS, SOUTHEAST, AND MID-ATLANTIC, FRI-TUE, SEP 4-8.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN GREAT
BASIN, NORTHERN ROCKIES, AND NORTHERN HIGH PLAINS, FRI-SAT, SEP 4-5.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF SOUTHERN ARIZONA AND
SOUTHWESTERN NEW MEXICO, FRI-MON, SEP 4-7.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS
AND THE LOWER AND MIDDLE MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR SUNDAY AUGUST 30 - THURSDAY SEPTEMBER 03:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY SEPTEMBER 04 - THURSDAY SEPTEMBER 10: WHILE YESTERDAY'S ECMWF
ENSEMBLE HINTED AT A POTENTIAL BREAK IN THE EXTREME HEAT ACROSS THE CENTRAL
U.S., TODAY'S 0Z ECMWF HAS JUMPED BACK TO A MORE PERSISTENT MID-LEVEL RIDGE
ACROSS THE REGION, AGREEING WITH THE 0Z GEFS. THIS FAVORS ANOMALOUSLY WARM
TEMPERATURES (UPWARDS OF +10 DEG F ABOVE NORMAL) CONTINUING ACROSS THE CENTRAL
AND SOUTHERN PLAINS AND ADJACENT AREAS OF THE MISSISSIPPI VALLEY THROUGH AT
LEAST LABOR DAY WEEKEND. THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOLS (PETS)
DEPICT PROBABILITIES OF 40-60 PERCENT FOR MAXIMUM TEMPERATURES EXCEEDING THE
90TH CLIMATOLOGICAL PERCENTILE EARLY IN THE PERIOD, WITH A VERY STRONG SIGNAL
ALSO BEING DEPICTED IN 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 IS NUDGED SLIGHTLY NORTHWARD COMPARED TO YESTERDAY AND IS
NOW VALID FOR SEP 4-6. WHILE TOOLS ARE MARGINALLY SUPPORTIVE OF A HIGH RISK, IT
WAS NOT INCLUDED DUE TO THE VARYING ECMWF GUIDANCE, AS WELL AS CONSIDERATION OF
THE 0Z CANADIAN ENSEMBLE WHICH CONTINUES TO BE MORE ROBUST WITH TROUGHING
MOVING ACROSS THE NORTH-CENTRAL CONUS AND RESULTANT DECREASE IN HEIGHTS ACROSS
THE PLAINS DURING WEEK-2. THE SLIGHT RISK IS NOW VALID THROUGH SEP 8 AND
EXTENDS THROUGHOUT MUCH OF THE MIDWEST, AND ALSO INTO THE SOUTHEAST AND
MID-ATLANTIC. WHILE POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST THROUGHOUT
THE PERIOD, THE DECLINING TEMPERATURE CLIMATOLOGY AND SHORTENING DAYLIGHT HOURS
REDUCE CONFIDENCE REGARDING EXTREME HEAT.
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 LOWER MISSISSIPPI VALLEY, AND IS EXPANDED
FARTHER NORTH INTO THE MIDDLE 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 LEADS TO INCREASED
ONSHORE FLOW AND MOISTURE ADVECTION FAVORING ABOVE-NORMAL PRECIPITATION OVER
MUCH OF THE WEST. 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, AND 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 4-5. 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, WITH THE NATIONAL HURRICANE CENTER
(NHC) MONITORING FOUR SEPARATE AREAS OF ADDITIONAL DEVELOPMENT IN THE NEXT
WEEK. ONE AREA CURRENTLY LOCATED NEAR 135 DEG E HAS A 90 PERCENT CHANCE OF
DEVELOPMENT (AS OF 11AM PDT) WHERE BOTH ENSEMBLES AND PROBABILISTIC TOOLS SHOW
THIS POTENTIAL SYSTEM TRACKING WESTWARD TO THE SOUTH OF HAWAII MUCH IN THE SAME
MANNER AS LALA AND MOKE. 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 3-DAY PRECIPITATION VALUES EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE ACROSS THE STATE.
TWO OTHER WATCH AREAS ARE BEING MONITORED CLOSER TO MEXICO WITH HIGH CHANCES OF
DEVELOPMENT, WITH THESE DISTURBANCES TRACKING NORTHWESTWARD. AS A RESULT, THERE
IS SOME POTENTIAL FOR A GULF SURGE EVENT AND MOISTURE ADVENTION INTO THE DESERT
SOUTHWEST. WHILE TOOLS ARE FAIRLY WEAK WITH A HEAVY PRECIPITATION POTENTIAL,
THERE IS STILL SOME SUPPORT IN THE RAW TOOLS DEPICTING INCREASED PRECIPITATION
AMOUNTS, AND THE PETS DEPICT INCREASED CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE
85TH CLIMATOLOGICAL PERCENTILE AND A HALF-INCH DURING THE FIRST HALF OF WEEK-2.
THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR PORTIONS OF
SOUTHERN ARIZONA AND NEW MEXICO FOR SEP 4-7.
TROPICAL STORM DOLLY HAS FORMED ACROSS THE ATLANTIC MAIN DEVELOPMENT REGION
(NEAR 40 DEG W). HOWEVER, NHC FAVORS A WEAKENING OF THIS SYSTEM AS IT
APPROACHES THE LEEWARD ISLANDS.
COLDER TEMPERATURES ARE ALSO PREDICTED FOR THE BROOKS RANGE IN NORTHERN ALASKA
DURING WEEK-2. THOUGH PRECIPITATION AMOUNTS ARE NOT EXPECTED TO REACH HAZARDOUS
CRITERIA, THE REGION MAY EXPERIENCE ITS FIRST SNOWFALL OF THE SEASON.
FORECASTER: THOMAS COLLOW
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