186
FXUS21 KWNC 211847
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 21 2025
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST TO BUILD OVER THE INTERIOR
WESTERN CONTIGUOUS U.S. (CONUS) AT THE OUTSET OF WEEK-2. THIS FAVORS A RETREAT
OF THE MEAN MID-LEVEL LOW BACK TOWARD THE NORTHEAST PACIFIC AND GULF OF ALASKA
AND A SUBSEQUENT DECREASE IN ATMOSPHERIC RIVER ACTIVITY INTO THE WEST COAST
COMPARED TO WEEK-1. HOWEVER, OCCASIONAL ROUNDS OF HEAVY PRECIPITATION AND HIGH
WINDS REMAIN POSSIBLE ACROSS THE NORTHWESTERN CONUS AND SOUTHEASTERN ALASKA
THROUGHOUT THE PERIOD. MODELS CONTINUE TO TREND STRONGER WITH MID-LEVEL LOW
PRESSURE ACROSS THE EASTERN U.S., FAVORING INCREASED WINDS ACROSS THE GREAT
PLAINS ON ITS BACKSIDE. SURFACE LOW PRESSURE IN ASSOCIATION WITH THIS TROUGH
FAVORS ENHANCED PRECIPITATION ACROSS THE EASTERN SEABOARD IN THE DAYS LEADING
UP TO AND INCLUDING HALLOWEEN. WHILE UNCERTAINTY IS HIGH, THERE ARE INDICATIONS
THAT SOME MOISTURE FROM TROPICAL STORM MELISSA CURRENTLY OVER THE CARIBBEAN MAY
BE DRAWN INTO THE SYSTEM, FURTHER ENHANCING PRECIPITATION IN THE EAST.
HAZARDS
MODERATE RISK OF HIGH WINDS ACROSS PORTIONS OF THE PACIFIC NORTHWEST, WED-SUN,
OCT 29-NOV 2.
MODERATE RISK OF HIGH WINDS ACROSS THE NORTHERN AND CENTRAL PLAINS, AND
NEIGHBORING PORTIONS OF THE MISSISSIPPI VALLEY, WED-THU, OCT 29-30.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE PACIFIC NORTHWEST, WED-TUE,
OCT 29-NOV 4.
SLIGHT RISK OF HIGH WINDS ACROSS MUCH OF THE GREAT PLAINS EXTENDING INTO THE
NORTHEASTERN CONUS AND MID-ATLANTIC, WED-SAT, OCT 29-NOV 1.
MODERATE RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHEAST,
MID-ATLANTIC, AND APPALACHIANS, WED-FRI, OCT 29-31.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE OHIO AND TENNESSEE
VALLEYS, SOUTHEAST, APPALACHIANS, NORTHEAST, AND MID-ATLANTIC, WED-SAT, OCT
29-NOV 1.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS NORTHERN CALIFORNIA AND THE PACIFIC
NORTHWEST, WED-TUE, OCT 29-NOV 4.
SLIGHT RISK OF HEAVY SNOW ACROSS THE CASCADES, WED-TUE, OCT 29-NOV 4.
SLIGHT RISK OF HIGH WINDS ACROSS COASTAL SOUTHEASTERN ALASKA, WED-SUN, OCT
29-NOV 2.
DETAILED SUMMARY
FOR FRIDAY OCTOBER 24 - TUESDAY OCTOBER 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY OCTOBER 29 - TUESDAY NOVEMBER 04: DURING WEEK-1, ENHANCED
ATMOSPHERIC RIVER ACTIVITY IS FORECAST ACROSS THE WEST COAST OF THE CONUS.
HOWEVER, BY THE OUTSET OF WEEK-2, THE 0Z ECENS, GEFS, AND CMCE DEPICT RIDGING
BUILDING ACROSS THE WEST, WITH THE 0Z ECENS MOST AMPLIFIED SHOWING +150 METER
POSITIVE HEIGHT ANOMALIES OVER PORTIONS OF THE GREAT BASIN AND ROCKIES. THIS
EVOLUTION WOULD FAVOR LONGWAVE TROUGHING RETREATING INTO THE NORTHEASTERN
PACIFIC AND GULF OF ALASKA RESULTING IN DECREASING ATMOSPHERIC RIVER ACTIVITY
ALONG THE WEST COAST. HOWEVER, GIVEN THE PROXIMITY OF THE ANOMALOUS TROUGHING
AND THE PROJECTED WEAKENING OF THE RIDGE AMPLITUDE WITH TIME, ENHANCED ONSHORE
FLOW AND INTERMITTENT ROUNDS OF HEAVY PRECIPITATION AND HIGH WINDS ARE FAVORED
TO PERSIST ACROSS THE PACIFIC NORTHWEST. THE GEFS AND ECENS PROBABILISTIC
EXTREMES TOOLS (PETS) DEPICT AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION
TOTALS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH THROUGHOUT WEEK-2
ACROSS THE NORTHWESTERN CONUS, WITH THE ECENS PET DEPICTING THE STRONGEST
PROBABILITIES DURING THE MIDDLE OF THE PERIOD. ADDITIONALLY, INTEGRATED VAPOR
TRANSPORT (IVT) DERIVED FROM THE GEFS AND ECENS ENSEMBLE MEANS HOVERS AROUND
250 KG/M/S DURING WEEK-2 ACROSS THE COASTAL NORTHWEST. ALTHOUGH PRECIPITATION
TOTALS IN THE UNCALIBRATED TOOLS ARE LOWER COMPARED TO THE WEEK-1 PERIOD, THE
PERSISTENT SIGNAL IN THE PETS AND IVT TOOLS SUPPORT A SLIGHT RISK FOR HEAVY
PRECIPITATION ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA FOR ALL OF
WEEK-2. A CORRESPONDING SLIGHT RISK OF HEAVY SNOW IS POSTED ACROSS THE
CASCADES. GIVEN THE DECREASING PRECIPITATION TOTALS IN WEEK-2, THE FLOODING
POSSIBLE HAZARD IS REMOVED.
A MODERATE RISK FOR HIGH WINDS REMAINS HIGHLIGHTED OVER PORTIONS OF WESTERN
WASHINGTON AND NORTHWESTERN OREGON, OCT 29-NOV-2, WHERE WIND SPEEDS 25-35 MPH
ARE POSSIBLE WITH HIGHER GUSTS. THE PROBABILISTIC SIGNAL IN THE ECENS PET
INCREASES FURTHER NORTH, WITH AT LEAST A 40 PERCENT CHANCE WIND SPEEDS EXCEED
THE 85TH CLIMATOLOGICAL PERCENTILE OVER THE OLYMPIC PENINSULA. A SLIGHT RISK
FOR HIGH WINDS CONTINUES FOR ALL OF WEEK-2 EXTENDING SOUTH TO THE
OREGON/CALIFORNIA BORDER. A SLIGHT RISK FOR HIGH WINDS IS ALSO POSTED ACROSS
COASTAL SOUTHEASTERN MAINLAND AND SOUTHEAST ALASKA, OCT 29-NOV-2, WHERE A
SURFACE LOW IS PREDICTED TO MOVE OVER THE GULF OF ALASKA INCREASING THE
SOUTHEASTERLY FLOW, WITH THE ECENS PET DEPICTING PROBABILITIES OF AT LEAST 20
PERCENT FOR WIND SPEEDS EXCEEDING 40-MPH. ENHANCED PRECIPITATION IS ALSO
POSSIBLE ACROSS COASTAL SOUTHEASTERN ALASKA, BUT THE HIGHEST TOTALS ARE MORE
LIKELY FURTHER SOUTH ACROSS BRITISH COLUMBIA. THEREFORE, NO RELATED
PRECIPITATION HAZARD IS POSTED FOR ALASKA.
A POTENT SHORTWAVE TROUGH IS FORECAST TO TRACK ACROSS THE CENTRAL AND EASTERN
CONUS DURING THE FIRST HALF OF WEEK-2. WHILE PRECIPITATION IS FORECAST TO EXIT
BY THE START OF THE PERIOD, A STRONG SURFACE PRESSURE GRADIENT IS ANTICIPATED
TO DEVELOP ACROSS THE GREAT PLAINS ON THE BACKSIDE OF THE TROUGH AND TO THE
EAST OF SURFACE HIGH PRESSURE OVER THE ROCKIES. THE UNCALIBRATED 0Z ECENS AND
GEFS DEPICT 30-50 PERCENT CHANCES OF WIND SPEEDS EXCEEDING 25-MPH ACROSS THE
REGION, WITH A CORRESPONDING ENHANCED SIGNAL IN THE ECENS PET. THEREFORE, A
MODERATE RISK OF HIGH WINDS REMAINS POSTED ACROSS THE NORTHERN AND CENTRAL
PLAINS, AND NEIGHBORING PORTIONS OF THE MISSISSIPPI VALLEY, OCT 29-30. WINDS
ARE FORECAST TO DIMINISH AS THE TROUGH MOVES FURTHER EAST, WITH A BROAD SLIGHT
RISK OF HIGH WINDS REMAINING ACROSS MUCH OF THE GREAT PLAINS EXTENDING INTO THE
NORTHEASTERN CONUS AND MID-ATLANTIC, OCT 29-NOV 1, WHERE WIND SPEEDS MAY EXCEED
20-MPH BASED ON THE ECENS PET.
AS THE TROUGHING MOVES FURTHER EAST, FRONTAL ACTIVITY AND POSSIBLE SURFACE LOW
PRESSURE ARE PREDICTED TO BRING INCREASED PRECIPITATION CHANCES TO THE EAST.
THE FORECAST IS FURTHER COMPLICATED BY THE EVOLUTION OF TROPICAL STORM MELISSA,
CURRENTLY OVER THE CARIBBEAN. INDIVIDUAL ENSEMBLE MEMBERS FROM THE GEFS AND
ECENS VARY GREATLY WITH MELISSA, WITH A MORE WEST-BASED TRACK CURRENTLY MORE
FAVORED IN THE ECENS. SLOWER SOLUTIONS ARE CONCERNING GIVEN THE POSSIBILITY FOR
MORE FRONTAL INTERACTION WITH THE UPSTREAM TROUGH. THE 0Z ECENS AND PREVIOUS
DETERMINISTIC ECMWF RUNS ARE VERY WET ACROSS THE NORTHEAST AND MID-ATLANTIC
AROUND THE END OF OCTOBER AS THE AFOREMENTIONED FRONT DRAWS UP TROPICAL
MOISTURE FROM MELISSA. HOWEVER, THE GEFS HAS ALSO BEEN TRENDING WETTER, WITH
BOTH THE ECENS AND GEFS PETS DEPICTING ENHANCED SIGNALS FOR HEAVY PRECIPITATION
IN THE EAST DURING THIS TIMEFRAME. THE UNCALIBRATED ECENS (GEFS) ALSO INDICATES
AT LEAST A 40 (30) PERCENT CHANCE OF DAY 8-10 (OCT 29-31) PRECIPITATION TOTALS
EXCEEDING 1-INCH. WHILE UNCERTAINTY REMAINS HIGH IN REGARDS TO THE EXACT
EVOLUTION, ESPECIALLY IN REGARDS TO ANY TROPICAL CYCLONE INTERACTION, A
MODERATE RISK FOR HEAVY PRECIPITATION IS HIGHLIGHTED ACROSS PORTIONS OF THE
NORTHEAST, MID-ATLANTIC, AND APPALACHIANS, OCT 29-31, GIVEN THE INCREASING
PRECIPITATION SIGNALS IN THE MODELS, ALONG WITH CONSIDERATION THAT THIS PERIOD
LEADS UP TO AND INCLUDES HALLOWEEN. A SLIGHT RISK OF HEAVY PRECIPITATION
CONTINUES THROUGH NOV 1.
FORECASTER: THOMAS COLLOW
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