290
FXUS21 KWNC 101818
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 10 2026
SYNOPSIS: DEAMPLIFYING MID-LEVEL HIGH PRESSURE IS FAVORED THROUGHOUT MUCH OF
THE CONTIGUOUS U.S. (CONUS) RESULTING IN A LOWERED RISK OF EXTREME HEAT
CONDITIONS DURING WEEK-2. THE GREATEST RISK OF EXTREME HEAT LOOKS TO BE FOCUSED
OVER PARTS OF THE NORTHWESTERN AND NORTHCENTRAL CONUS IN PROXIMITY TO THE
ANOMALOUS MID-LEVEL HIGH PRESSURE FORECAST. DOWNSTREAM, MORE MID-LEVEL LOW
PRESSURE IS FAVORED EARLY IN WEEK-2, WHICH IS EXPECTED TO BRING COOLER
TEMPERATURES AND ALLAY HEAT CONCERNS FOR MANY AREAS EAST OF THE MISSISSIPPI.
HOWEVER, SURFACE LOW DEVELOPMENT OVER THE SOUTHEAST INCREASES THE RISK OF HEAVY
PRECIPITATION, AS WELL AS FAVORED ENHANCED SUBTROPICAL RIDGING TO PROMOTE A
LINGERING HEAT RISK FOR THE EASTERN GULF OF AMERICA STATES. THIS PREVAILING
MID-LEVEL PATTERN IS ALSO CONSISTENT WITH AN ENHANCED MONSOONAL CIRCULATION,
POTENTIALLY BRINGING TROPICAL MOISTURE AND A RISK OF HEAVY PRECIPITATION INTO
PARTS OF THE SOUTHWESTERN CONUS.
HAZARDS
MODERATE RISK OF EXTREME HEAT ACROSS THE NORTHERN AND CENTRAL PLAINS, ADJACENT
PARTS OF THE MISSISSIPPI VALLEY, ROCKIES AND NORTHERN GREAT BASIN, SAT-SUN, JUL
18-19.
MODERATE RISK OF EXTREME HEAT ACROSS PORTIONS OF THE FLORIDA PENINSULA SAT-SUN,
JUL 18-19.
SLIGHT RISK OF EXTREME HEAT ACROSS PARTS OF CALIFORNIA, PACIFIC NORTHWEST,
GREAT BASIN, ROCKIES, NORTHERN AND CENTRAL PLAINS, MIDDLE AND UPPER MISSISSIPPI
VALLEY, SAT-WED, JUL 18-22.
SLIGHT RISK OF EXTREME HEAT FOR COASTAL PORTIONS OF THE LOWER MISSISSIPPI
VALLEY AND SOUTHEAST SAT-FRI, JUL 18-24.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE LOWER EASTERN SEABOARD, SAT-MON, JUL
18-20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE FOUR CORNERS, SAT-WED, JUL
18-22.
RAPID ONSET DROUGHT RISK ACROSS THE NORTHERN PLAINS.
DETAILED SUMMARY
FOR MONDAY JULY 13 - FRIDAY JULY 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JULY 18 - FRIDAY JULY 24: LATE IN WEEK-1, DYNAMICAL MODEL 500-HPA
HEIGHT ANOMALY FORECASTS FROM THE GEFS AND ECMWF ENSEMBLES REMAIN IN GOOD
AGREEMENT FEATURING ANOMALOUS MID-LEVEL RIDGING OVERSPREADING MUCH OF THE
CONUS. A HIGHLY AMPLIFIED MID-LEVEL HEIGHT ANOMALY CENTER CONTINUES TO BE
FAVORED OVER THE NORTH-CENTRAL CONUS, ALONG WITH A SECONDARY RIDGE CENTER
EXTENDING EASTWARD INTO THE MID-ATLANTIC AND THE SOUTHEAST, BOTH OF WHICH ARE
EXPECTED TO PROMOTE ELEVATED RISKS OF EXTREME HEAT COINCIDING WITH THE
CLIMATOLOGICAL PEAK OF SUMMERTIME HEATING. BY THE OUTSET OF WEEK-2 (JUL 18),
THERE IS INCREASED MODEL SUPPORT FOR THE EASTWARD EXTENSION OF THIS 500-HPA
RIDGE TO DEAMPLIFY IN THE MODELS, WITH THE LATEST 0Z ECMWF ENSEMBLE FEATURING A
FAIRLY SWIFT TRANSITION TOWARDS DEVELOPING A MEAN TROUGH, WITH NEGATIVE HEIGHT
DEPARTURES CENTERED OVER THE EASTERN U.S. ON DAY 9. THE DEPTH OF THE MEAN
TROUGH AXIS HAS BECOME INCREASINGLY PRONOUNCED COMPARED TO PREVIOUS ECMWF
ENSEMBLE GUIDANCE OVER THE PAST FEW DAYS. BY COMPARISON, THE 0Z GEFS IS SLOWER
WITH THIS TRANSITION, BUT NONETHELESS FAVORS LOWERING HEIGHTS AND MORE
NORTHWESTERLY FLOW TO MITIGATE A LINGERING EXTREME HEAT RISK WITH COOLER
TEMPERATURES. CONCURRENT WITH THE DEAMPLIFYING RIDGING OVER THE EASTERN U.S.
EARLY IN THE PERIOD, MUCH OF THE MID-LEVEL RIDGING UPSTREAM IS ALSO FAVORED TO
WEAKEN, THOUGH POSITIVE HEIGHT DEPARTURES REMAIN FAVORED TO SUSTAIN AN
INCREASED HEAT RISK OVER MANY PARTS OF THE WESTERN CONUS AT LEAST THROUGH THE
MIDDLE OF THE PERIOD.
BASED ON THE DEAMPLIFYING PATTERN, WITH MORE TROUGHING AND COOLER TEMPERATURES
FAVORED OVER THE EASTERN U.S. EARLY IN THE PERIOD, THE HIGH RISK EXTREME HEAT
IS DISCONTINUED OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY IN THE
UPDATED OUTLOOK, AS THE HOTTEST TEMPERATURES LOOK TO TIME OFF DURING WEEK-1.
HOWEVER, A MODERATE RISK (40-60% CHANCE) OF EXTREME HEAT REMAINS ISSUED OVER
THE NORTHERN AND CENTRAL PLAINS (JUL 18-19), WITH ITS COVERAGE EXPANDED TO
INCLUDE MORE OF THE INTERIOR WEST AND WESTERN PORTIONS OF THE HIGH PLAINS IN
PROXIMITY TO THE ANOMALOUS RIDGE CENTER. THE MODERATE RISK COVERAGE IS REMOVED
OVER THE MISSISSIPPI, TENNESSEE AND OHIO VALLEYS, AND GREAT LAKES DUE TO COOLER
TEMPERATURES FAVORED IN THE RAW AND CALIBRATED TOOLS OVER THIS PART OF THE
COUNTRY. WITHIN THE MODERATE RISK AREA, THERE REMAINS INCREASED CHANCES FOR
HEAT INDEX VALUES EXCEEDING 100 (105) DEG F IN THE NORTHERN (CENTRAL) PLAINS,
WITH THE UNCALIBRATED ECMWF AND GEFS SHOWING ELEVATED CHANCES (>30%) FOR DOUBLE
DIGIT POSITIVE TEMPERATURE DEPARTURES, AND THE GEFS PROBABILISTIC EXTREMES TOOL
(PET) INDICATING SIMILAR CHANCES FOR DAYTIME TEMPERATURES EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE FOR THE FIRST FEW DAYS OF PERIOD. DESPITE A SMALL
TILT TOWARDS NEAR TO ABOVE-NORMAL PRECIPITATION FAVORED FOR THE DAKOTAS DURING
WEEK-2, THE COMBINATION OF ANOMALOUS WARMTH AND ANTECEDENT DRYNESS SUPPORTS AN
ENHANCED RISK OF RAPID ONSET DROUGHT ACROSS PORTIONS OF THE NORTHERN PLAINS.
SURROUNDING THE MODERATE RISK AREA, A SLIGHT RISK OF EXTREME HEAT REMAINS IS
POSTED FOR MUCH OF THE WESTERN CONUS, EXCLUDING THE PARTS OF THE LOWER FOUR
CORNERS WHERE TEMPERATURES TOOLS INDICATE COOLER TEMPERATURES ASSOCIATED WITH
AN UPTICK IN MONSOONAL PRECIPITATION (DISCUSSED BELOW). THERE CONTINUES TO BE
DECENT SIGNALS IN THE UNCALIBRATED 0Z GEFS AND ECMWF ENSEMBLES FOR TEMPERATURES
ABOVE 100 DEG F ACROSS LOW ELEVATION AREAS OF THE GREAT BASIN AND ROCKIES, AND
POSSIBLY ABOVE 105 DEG F ACROSS THE CALIFORNIA CENTRAL VALLEY SUPPORTING THE
SLIGHT RISK AREA. THE SLIGHT RISK REMAINS VALID THROUGH JUL 22, AS MODELS FAVOR
MORE OF A ZONAL PATTERN DEVELOPING OVER THE CONUS LATE IN WEEK-2, WITH WEAKLY
POSITIVE MID-LEVEL HEIGHT DEPARTURES LIMITED TO THE HIGHER LATITUDES IN CANADA.
EVEN WITH COOLER TEMPERATURES FAVORED OVER THE EASTERN U.S. ENHANCED
SUBTROPICAL RIDGING AND ACCOMPANYING HEAT RISKS STILL REMAINS A CONCERN OVER
THE GULF STATES. BOTH PETS MAINTAIN AT LEAST 20% CHANCES OF MAXIMUM
TEMPERATURES EXCEEDING THE 85TH PERCENTILE OVER PARTS OF LOWER MISSISSIPPI
VALLEY AND THE SOUTHEAST, WITH THE ECMWF PET FAVORING HIGHER CHANCES (>40%) FOR
EXCEEDING THIS THRESHOLD CONCENTRATED OVER THE FLORIDA PENINSULA. IN ADDITION,
SEA SURFACE TEMPERATURES IN THE EASTERN GULF CONTINUE TO RUN VERY WARM, WITH
ANOMALIES REGISTERING UPWARDS OF 2 DEGREES C TO SUPPORT CONTINUED SURFACE
WARMTH. THEREFORE, A SLIGHT RISK OF EXTREME HEAT IS POSTED ALONG THE COAST FROM
LOUISIANA TO FLORIDA FOR JUL 18-24, WITH AN EMBEDDED MODERATE RISK AREA (JUL
18-19) OVER PARTS OF CENTRAL AND SOUTHERN FLORIDA WHERE THE NATIONAL BLEND OF
MODELS (NBM) HIGHLIGHTS SEVERAL LOCATIONS WITH WARM HIGHS AND LOWS NEARING OR
BREAKING DAILY RECORDS EARLY IN THE PERIOD.
TIED TO MORE TROUGHING FAVORED OVER THE EASTERN U.S., THERE IS INCREASED
ENSEMBLE SUPPORT FOR SURFACE LOW DEVELOPMENT TO THE NORTH OF THE SUBTROPICAL
RIDGE OVER PARTS OF THE SOUTHEAST AND THE MID-ATLANTIC. WHILE THE GEFS PET
REMAINS RATHER MUTED WITH A HEAVY PRECIPITATION RISK, THE ECMWF PET NOW FAVORS
INCREASED CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1 INCH,
WITH THE UNCALIBRATED GEFS AND ECMWF SHOWING A SIGNIFICANT INCREASE IN THE
EXCEEDANCE PROBABILITIES RELATIVE TO YESTERDAY. THEREFORE, A SLIGHT RISK OF
HEAVY PRECIPITATION IS POSTED OVER MUCH OF THE LOWER EASTERN SEABOARD FOR JUL
18-20. BASED ON THE PETS, ELEVATED WIND SPEEDS ARE ALSO POSSIBLE WITHIN THE
SLIGHT PRECIPITATION RISK AREA, THOUGH THERE REMAINS A FAIR AMOUNT OF ENSEMBLE
SPREAD IN REGARDS TO STRENGTH AND POSITION OF THE LOW TO INDUCE HAZARDOUS WINDS
ONSHORE, THUS NO CORRESPONDING WIND HAZARD IS POSTED.
TRIPLE-DIGIT DAYTIME TEMPERATURES OVER THE SONORAN DESERT ARE LIKELY TO INDUCE
THERMAL SURFACE LOW PRESSURE, WHICH COMBINED WITH THE RIDGE AXIS POSITIONED
NEAR THE FOUR CORNERS, IS EXPECTED TO ADVECT TROPICAL MOISTURE NORTHWARD INTO
THE REGION, KICKING OFF THE SOUTHWEST MONSOON SEASON. IN ADDITION, THE NATIONAL
HURRICANE CENTER (NHC) IS CURRENTLY MONITORING MULTIPLE AREAS FOR TROPICAL
CYCLONE (TC) DEVELOPMENT IN THE CENTRAL AND EASTERN PACIFIC, WITH ONE AREA
CLOSER TO MEXICO WITH 70% CHANCES FOR FORMATION DURING THE NEXT SEVEN DAYS.
SHOULD FORMATION OCCUR NEXT WEEK, A POTENTIAL TRACK NEARING THE GULF OF
CALIFORNIA COULD INITIATE A GULF SURGE AND BRING ADDITIONAL MOISTURE AND
PRECIPITATION INTO THE SOUTHWEST. THERE CONTINUES TO BE GOOD SUPPORT IN THE
GEFS AND ECMWF PETS INDICATING 20-40% CHANCES FOR 3-DAY ACCUMULATED AMOUNTS
EXCEEDING THE 85TH PERCENTILE, AND A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS
POSTED FOR MUCH OF THE FOUR CORNERS (JUL 18-22). THE FAVORED UPTICK IN
MONSOONAL ACTIVITY IS LIKELY TO KEEP AN EXCESSIVE HEAT RISK AT BAY DURING THE
PERIOD, HOWEVER, MONSOONAL THUNDERSTORMS CAN ALSO PRODUCE DRY LIGHTNING,
RESULTING IN INCREASED WILDFIRE RISK. GIVEN THE STRONGER SIGNALS FOR
ABOVE-NORMAL TEMPERATURES FURTHER NORTH, THERE IS ALSO AN INCREASED RISK OF
WILDFIRES ACROSS THE INTERIOR WEST AND HIGH PLAINS AS WELL.
FORECASTER: NICK NOVELLA
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