979
FXUS21 KWNC 261822
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 26 2026
SYNOPSIS: A LINGERING AREA OF MID-LEVEL HIGH PRESSURE OVER THE SOUTHERN TIER OF
THE CONTIGUOUS U.S. (CONUS) SUPPORTS A CONTINUED RISK OF EXCESSIVE HEAT, WITH
THE GREATEST RISK FOCUSED OVER THE SOUTHERN PLAINS AND LOWER MISSISSIPPI
VALLEY EARLY IN THE PERIOD. TIED TO A STRENGTHENING AREA OF MID-LEVEL HIGH
PRESSURE OVER THE NORTHEASTERN PACIFIC, THERE IS GROWING SUPPORT FOR STRONG
COLD AIR ADVECTION TO BRING MUCH BELOW NORMAL TEMPERATURES OVER PARTS OF THE
NORTHWESTERN CONUS. ENHANCED MOISTURE ADVECTION FAVORED OVER THE SOUTHWESTERN
CONUS TOWARDS THE LATER PART OF NEXT WEEK 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 MIDDLE AND LOWER MISSISSIPPI VALLEY.
HAZARDS
MODERATE RISK OF EXTREME HEAT FOR PARTS OF THE SOUTHERN AND CENTRAL PLAINS,
LOWER AND MIDDLE MISSISSIPPI VALLEY, WESTERN PORTIONS OF THE TENNESSEE AND OHIO
VALLEYS, AND THE SOUTHEAST, THU, SEP 3.
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE GREAT PLAINS, MISSISSIPPI, OHIO,
AND TENNESSEE VALLEYS, SOUTHEAST, AND MID-ATLANTIC, THU-SUN, SEP 3-6.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHERN GREAT
BASIN, NORTHERN ROCKIES, AND NORTHERN HIGH PLAINS, THU-SAT, SEP 3-5.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF SOUTHERN ARIZONA AND
SOUTHWESTERN NEW MEXICO, SAT-MON, SEP 5-7.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS,
THE LOWER MISSISSIPPI VALLEY AND ADJACENT AREAS.
DETAILED SUMMARY
FOR SATURDAY AUGUST 29 - WEDNESDAY SEPTEMBER 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY SEPTEMBER 03 - WEDNESDAY SEPTEMBER 09: OVER THE PAST WEEK OR SO,
DYNAMICAL MODELS HAVE BEEN CONSISTENT IN FAVORING A FAIRLY STABLE 500-HPA
HEIGHT PATTERN, WITH THE MAIN HEIGHT FEATURES CONSISTING OF ENHANCED
SUBTROPICAL RIDGING OVER THE SOUTHERN TIER OF THE CONUS WITH AN ANOMALOUS RIDGE
AXIS EXTENDING NORTHWARD INTO CANADA, BOOKENDED BY A PAIR OF MEAN TROUGHS OVER
THE NORTHWESTERN AND NORTHEASTERN CONUS. HOWEVER, SINCE YESTERDAY, BOTH THE
GEFS AND ECMWF HAVE FALLEN MORE OUT OF PHASE WITH ONE ANOTHER. WHILE BOTH
MODELS ARE IN AGREEMENT IN AMPLIFYING A SECONDARY AMPLIFIED RIDGE CENTER OVER
THE NORTHEASTERN PACIFIC, THE ECMWF IS MORE PROGRESSIVE WITH A MEAN TROUGH
BEING FORCED DOWNSTREAM, WHICH ERODES MUCH OF ABOVE-NORMAL HEIGHTS THAT HAVE
PERSISTED THROUGHOUT THE WESTERN AND CENTRAL CONUS, WHILE ALSO SHIFTING THE
RIDGE AXIS INTO THE EASTERN CONUS TOWARDS THE MIDDLE OF THE PERIOD. THE GEFS,
ON THE OTHER HAND, FAVORS A MUCH MORE STABLE PATTERN, MAINTAINING THE MEAN
TROUGHING ESTABLISHED OVER THE NORTHWESTERN AND NORTHEASTERN CONUS, WITH SOME
SUPPRESSION OF THE ENHANCED SUBTROPICAL RIDGING OVER THE SOUTHERN TIER OF THE
U.S. AS A RESULT OF THESE DISCREPANCIES, THERE IS INCREASED UNCERTAINTY IN THE
UPDATED HAZARD OUTLOOK, PARTICULARLY BY THE MIDDLE OF THE PERIOD, WITH
IMPLICATIONS ON THE DURATION OF A LONG LIVED HEAT EVENT THAT HAS AFFECTED MUCH
OF THE SOUTHERN U.S. FOR MUCH OF AUGUST.
BASED ON DECLINING SUPPORT IN THE TEMPERATURE TOOLS WITH MUCH OF THE HOTTEST
TEMPERATURES TIMING OFF, THE HIGH RISK OF EXTREME HEAT IS DISCONTINUED IN THE
UPDATED OUTLOOK. HOWEVER, A MODERATE RISK OF EXTREME REMAINS ISSUED FOR DAY 8
(SEP 3), WHERE BOTH THE GEFS AND ECMWF PROBABISITIC EXTREME TOOLS (PETS) AGREE
IN FEATURING AT LEAST 30% CHANCES FOR DAYTIME TEMPERATURES EXCEEDING THE 90TH
PERCENTILE, ALONG WITH CONTINUED SUPPORT IN THE CALIBRATED HEAT TOOLS
INDICATING ELEVATED CHANCES FOR HEAT INDEX VALUES REACHING THE 90TH PERCENTILE.
BASED ON THE EASTWARD EXPANSION OF SIGNALS IN PERCENTILE SPACE IN THESE TOOLS,
THE MODERATE RISK AREA IS ADJUSTED TO INCLUDE PORTIONS OF THE TENNESSEE AND
OHIO VALLEYS AND THE SOUTHEAST, WITH COVERAGE REMOVED OVER THE SOUTHERN HIGH
PLAINS ASSOCIATED WITH COOLER TEMPERATURES BEING FAVORED. WITHIN THE
HIGHLIGHTED MODERATE RISK AREA, THERE CONTINUES TO BE GOOD MODEL SUPPORT FOR
DOUBLE DIGIT TEMPERATURE ANOMALIES, TRANSLATING TO DAYTIME TEMPERATURES LIKELY
EXCEEDING 95 AND 100 DEG F IN MANY LOCATIONS, WITH HEAT INDEX VALUES REACHING
110 DEG F WHERE HIGHER DEWPOINTS ARE EXPECTED ACROSS PARTS OF SOUTHERN TEXAS
AND THE LOWER MISSISSIPPI VALLEY. SURROUNDING THE MODERATE RISK AREA, A SLIGHT
RISK OF EXTREME HEAT REMAINS POSTED FOR MUCH OF THE SOUTH-CENTRAL AND
SOUTHEASTERN CONUS THROUGH SEP 6. WITH MORE TROUGHING OVER THE WEST COAST,
COVERAGE OF THE SLIGHT RISK IS REMOVED OVER MUCH OF THE DESERT SOUTHWEST, AND
IS NO LONGER VALID FOR THE ENTIRETY OF WEEK-2 DUE TO THE AFOREMENTIONED MODEL
DIFFERENCES ASSOCIATED WITH HOW THE TROUGHING EVOLVES FROM THE WEST. IN THE
ABSENCE OF EXCEPTIONALLY STRONG SUBTROPICAL RIDGING IN EARLY SEPTEMBER
(ENSEMBLES MAINTAIN LOW CHANCES FOR HEIGHTS EXCEEDING 594 DM BY DAY 11),
CHANCES FOR EXTREME HEAT BEING REALIZED ARE REDUCED GIVEN SHORTENING DAYLIGHT
HOURS, EVEN IN THE LOWER LATITUDES.
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 (AND PARTS OF 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.
THE AMPLIFYING RIDGE OVER THE NORTHEASTERN PACIFIC ALSO INTRODUCES THE
POTENTIAL FOR STRONGER COLD AIR ADVECTION INTO THE NORTHWESTERN CONUS EARLY IN
WEEK-2. BOTH ECMWF AND GEFS ENSEMBLES SHOW 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% 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 3-5. 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, WHERE THE NATIONAL HURRICANE CENTER
(NHC) IS CURRENTLY EYEING TWO ACTIVE TROPICAL CYCLONES (LALA AND ISELLE), ALONG
WITH FOUR WATCH AREAS FOR DEVELOPMENT IN THE TROPICAL WEATHER OUTLOOK (TWO).
ONE WATCH AREA CURRENTLY LOCATED NEAR 135E HAS 70% CHANCES 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.
TWO OTHER WATCH AREAS IN THE TWO ARE LOCATED CLOSER TO MEXICO, AND REGARDLESS
OF FORMATION DURING THE NEXT WEEK, A LOW TRACKING NEAR THE GULF OF CALIFORNIA
MAY TRIGGER A SURGE EVENT AND BRING ENHANCED MOISTURE INTO THE DESERT
SOUTHWEST. WHILE TOOLS ARE FAIRLY TENUOUS WITH A HEAVY PRECIPITATION POTENTIAL,
THERE IS STILL SOME SUPPORT IN THE RAW TOOLS DEPICTING INCREASED PRECIPITATION
AMOUNTS, AND CALIBRATED PETS SHOW A NORTHWARD EXPANDING AREA WITH INCREASED
CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE DURING THE MIDDLE OF
WEEK-2. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR PORTIONS
OF SOUTHERN ARIZONA AND NEW MEXICO FOR SEP 5-7. ELSEWHERE, ENSEMBLES POINT TO
MARGINAL HEAVY PRECIPITATION RISKS OVER PARTS OF THE MIDWEST AND ALONG PARTS OF
THE NORTHERN EASTERN SEABOARD EARLY IN THE PERIOD, HOWEVER NEITHER THE GEFS AND
ECMWF PETS ARE IN AGREEMENT IN THESE REGIONS, PRECLUDING ANY CORRESPONDING
HAZARDS.
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: NICK NOVELLA
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