508
FXUS21 KWNC 121810
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 12 2026
SYNOPSIS: EARLY IN WEEK-2, MID-LEVEL LOW PRESSURE IS FORECAST TO AMPLIFY ACROSS
THE WESTERN CONTIGUOUS U.S. (CONUS) ALONG WITH POTENTIAL SURFACE LOW PRESSURE
EJECTING OUT OF THE ROCKIES. THIS FAVORS INCREASED CHANCES OF HEAVY
PRECIPITATION DOWNSTREAM ACROSS THE GREAT PLAINS AND MISSISSIPPI VALLEY, HEAVY
SNOW OVER THE HIGHER ELEVATIONS OF THE ROCKIES, AND EPISODIC HIGH WINDS FROM
CALIFORNIA TO THE CENTRAL CONUS. FOLLOWING THE DEPARTURE OF THIS SYSTEM, A
BROAD AREA OF MID-LEVEL HIGH PRESSURE IS FORECAST OVER THE CENTRAL AND EASTERN
CONUS FAVORING MORE TRANQUIL WEATHER, AND ABOVE-NORMAL TEMPERATURES FOR MOST
AREAS EAST OF THE ROCKIES LATER IN OCTOBER.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND MIDDLE AND LOWER MISSISSIPPI VALLEY, TUE-THU, OCT 20-22.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE ROCKIES, TUE-WED, OCT 20-21.
SLIGHT RISK OF EPISODIC HIGH WINDS FROM CALIFORNIA THROUGH PORTIONS OF THE
GREAT BASIN, ROCKIES, PLAINS, AND UPPER MISSISSIPPI VALLEY, TUE-WED, OCT 20-21.
DETAILED SUMMARY
FOR THURSDAY OCTOBER 15 - MONDAY OCTOBER 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY OCTOBER 20 - MONDAY OCTOBER 26: THE 0Z ECMWF, GEFS, AND CANADIAN
ENSEMBLES DEPICT AN AMPLIFIED 500-HPA HEIGHT PATTERN ACROSS THE CONUS AT THE
START OF WEEK-2 WITH ANOMALOUS RIDGING ACROSS THE EAST, AND A TREND TOWARD
STRONGER SHORTWAVE TROUGHING OVER THE WEST COMPARED TO YESTERDAY. THE TROUGH
ACROSS THE WEST FAVORS POTENTIAL DEVELOPMENT OF A SURFACE LOW IN THE LEE OF THE
NORTHERN OR CENTRAL ROCKIES, WHICH, WHEN COMBINED WITH ENHANCED SOUTHERLY
RETURN FLOW ACROSS THE CENTRAL CONUS, PROVIDES A FAVORABLE SET-UP FOR ENHANCED
PRECIPITATION. THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT AN
EXPANSIVE AREA WITH PROBABILITIES UPWARDS OF 30 TO 40 PERCENT FOR 3-DAY
PRECIPITATION TO EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE THROUGHOUT MUCH OF
THE INTERIOR WEST INTO THE GREAT PLAINS AND MISSISSIPPI VALLEY. HOWEVER, THE
HIGHEST AMOUNTS (GREATER THAN 1-INCH IN 3-DAYS) ARE MOST LIKELY TO OCCUR ACROSS
THE MORE EASTERN AREAS AS REFLECTED IN THE UNCALIBRATED ECMWF AND GEFS
ENSEMBLES, WITH LOWER PRECIPITATION CLIMATOLOGIES LIKELY DRIVING THE HIGHER
PERCENTILE PROBABILITIES TO THE WEST. AS A RESULT, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS AND
THE MIDDLE AND LOWER MISSISSIPPI VALLEY, OCT 20-22.
FARTHER WEST, CLOSER TO THE DEVELOPING SURFACE LOW AND WITH COLD ENOUGH AIR AT
HIGHER ELEVATIONS, HEAVY SNOW IS POSSIBLE ACROSS THE ROCKIES. THE GEFS SNOW
WATER EQUIVALENT (SWE) PET DEPICTS PARTS OF THE REGION HAVING AT LEAST A 20
PERCENT CHANCE SWE EXCEEDS THE 85TH CLIMATOLOGICAL PERCENTILE AND A HALF-INCH.
IN ADDITION, THE UNCALIBRATED ECMWF ENSEMBLE DEPICTS SNOWFALL AMOUNTS GREATER
THAN 4 TO, IN SOME PLACES, 6 INCHES. GIVEN THE FAVORABLE SET-UP AND CONSIDERING
IT IS EARLY IN THE SEASON, A SLIGHT RISK OF HEAVY SNOW IS POSTED ACROSS
PORTIONS OF THE ROCKIES, OCT 20-21. THERE IS ALSO SUPPORT FOR A SLIGHT RISK OF
HIGH WINDS THROUGHOUT MUCH OF THE WESTERN AND CENTRAL CONUS AS THE SHORTWAVE
TROUGH MOVES THROUGH THE REGION. THIS IS EVIDENT IN BOTH THE PETS AND
UNCALIBRATED GUIDANCE, WHICH DEPICT AREAS WITH WIND SPEEDS POTENTIALLY
EXCEEDING 25-MPH, PARTICULARLY ACROSS THE CALIFORNIA COAST AND THE GREAT
PLAINS, WITH A MORE SPORADIC SIGNAL IN BETWEEN. THEREFORE A BROAD SLIGHT RISK
OF HIGH WINDS IS POSTED EXTENDING FROM CALIFORNIA THROUGH THE ROCKIES AND INTO
THE GREAT PLAINS/UPPER MISSISSIPPI VALLEY, ALSO FOR OCT 20-21.
FOLLOWING A COLDER PERIOD ACROSS THE EASTERN U.S. IN THE DAYS PRIOR TO THE
START OF WEEK-2, TEMPERATURES ARE FORECAST TO TREND WARMER AS ENHANCED RIDGING
SPREADS OVER THE REGION WITH THE DYNAMICAL MODELS DEPICTING +120 TO +180 METER
HEIGHT ANOMALIES OVER THE GREAT LAKES. THIS FAVORS UNSEASONABLY WARM WEATHER
ACROSS MUCH OF THE EASTERN HALF OF THE U.S. DURING WEEK-2 ALLOWING THE SLIGHT
RISK OF MUCH BELOW NORMAL TEMPERATURES TO BE DISCONTINUED. THE NATIONAL BLEND
OF MODELS (NBM) INDICATES THE POTENTIAL FOR RECORD WARMTH WITH HIGH
TEMPERATURES ABOVE 90 DEG F OVER THE LOWER MISSISSIPPI VALLEY, ALTHOUGH EXTREME
HEAT IS UNLIKELY TO BE A CONCERN THIS LATE IN THE YEAR PRECLUDING A RELATED
TEMPERATURE HAZARD. HOWEVER, WARMER TEMPERATURES COMBINED WITH ANY RESIDUAL
POWER OUTAGES RESULTING FROM HURRICANE ISAIAS COULD ADVERSELY IMPACT THOSE
WITHOUT ACCESS TO AIR CONDITIONING.
AN ACTIVE STORM TRACK IS FAVORED ACROSS THE NORTH PACIFIC DRIVEN BY ENHANCED
TROUGHING OVER THE BERING SEA ALONG WITH SOME POTENTIAL FOR RECURVING TROPICAL
CYCLONES OVER THE WEST PACIFIC. THE GEFS AND ECMWF ENSEMBLES DEPICT A SERIES OF
SURFACE LOWS ACROSS THE BERING SEA INTO THE GULF OF ALASKA, POTENTIALLY
IMPACTING SOUTHERN AND SOUTHEASTERN PARTS OF THE STATE. WHILE THE PETS ARE
MARGINALLY SUPPORTIVE OF SLIGHT RISKS OF HEAVY PRECIPITATION AND HIGH WINDS
OVER THESE AREAS, THERE IS CONSIDERABLE UNCERTAINTY TIED TO INDIVIDUAL TRACKS
AND TIMING. THEREFORE, NO HAZARDS ARE HIGHLIGHTED ACROSS ALASKA, BUT
INTERMITTENT PERIODS OF HEAVY PRECIPITATION AND HIGH WINDS ARE POSSIBLE ACROSS
THE EASTERN ALEUTIANS, SOUTHERN COASTAL MAINLAND, AND SOUTHEAST ALASKA
THROUGHOUT WEEK-2.
FORECASTER: THOMAS COLLOW
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