513
FXUS21 KWNC 201817
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT OCTOBER 20 2026
SYNOPSIS: TODAY'S MODEL ENSEMBLES PREDICT A MID-LEVEL TROUGH NEAR THE WEST
COAST AND A HIGHLY ANOMALOUS MID-LEVEL RIDGE OVER THE WESTERN GULF OF ALASKA
DURING WEEK-2. IN ADDITION, A LESS AMPLIFIED RIDGE OVER THE CENTRAL CONTIGUOUS
U.S. (CONUS) IS PREDICTED TO DEAMPLIFY AS IT MIGRATES EASTWARD ACROSS THE GREAT
LAKES AND NORTHEAST. SLIGHT RISK AREAS OF HEAVY PRECIPITATION ARE FAVORED
ACROSS MUCH OF THE WEST COAST AND FOUR CORNERS REGION IN ASSOCIATION WITH THE
WESTERN TROUGH, AND POSSIBLY AN INFLUX OF MOISTURE FROM THE EASTERN TROPICAL
PACIFIC. ENHANCED ONSHORE FLOW ACCOMPANYING THE WESTERN TROUGH ALSO PROMOTES A
SLIGHT RISK OF HEAVY SNOW FOR THE KLAMATH AND SIERRA MOUNTAIN RANGES IN
CALIFORNIA. SURFACE HIGH PRESSURE APPROACHING THE MID-ATLANTIC COAST EARLY IN
THE PERIOD, AND A DEVELOPING STORM OFF THE SOUTHEAST COAST, ARE FORECAST TO
RESULT IN A STRENGTHENED PRESSURE GRADIENT AND A RISK OF HIGH WINDS FOR THE
EAST COAST STATES. AS THE SURFACE HIGH MOVES OUT OVER THE WESTERN ATLANTIC
LATER IN THE PERIOD, SOUTHERLY RETURN FLOW IS FORECAST TO BRING A SLIGHT RISK
OF HEAVY PRECIPITATION FOR THE SOUTHERN HALF OF THE MISSISSIPPI VALLEY AND
PORTIONS OF NEIGHBORING STATES.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF ARIZONA, FRI-SUN, OCT
30-NOV 1.
SLIGHT RISK OF HEAVY PRECIPITATION FOR SOUTHERN PORTIONS OF THE FOUR CORNERS
AND WESTERN TEXAS, FRI-SUN, OCT 30-NOV 1.
SLIGHT RISK OF HEAVY SNOW FOR PARTS OF THE NORTHERN AND CENTRAL ROCKIES,
FRI-TUE, OCT 30-NOV 3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF OREGON AND CALIFORNIA,
FRI-TUE, OCT 30-NOV 3.
SLIGHT RISK OF HEAVY SNOW FOR THE KLAMATH AND SIERRA MOUNTAIN RANGES, FRI-TUE,
OCT 30-NOV 3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE LOWER MISSISSIPPI VALLEY
AND SOUTHERN PLAINS, FRI-TUE, OCT 30-NOV 3.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE EAST COAST, WED-FRI, OCT 28-30.
MODERATE RISK OF HIGH WINDS FOR PARTS OF WESTERN ALASKA, WED-FRI, OCT 28-30.
SLIGHT RISK OF HIGH WINDS FOR PARTS OF WESTERN ALASKA, THE ALASKA PENINSULA,
AND ALEUTIANS, WED-FRI, OCT 28-30.
DETAILED SUMMARY
FOR FRIDAY OCTOBER 23 - TUESDAY OCTOBER 27:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY OCTOBER 28 - TUESDAY NOVEMBER 03: A MID-LEVEL TROUGH NEAR THE
WEST COAST IS FORECAST TO BRING ENHANCED ONSHORE FLOW TO MUCH OF THE WEST BY
THE MIDDLE OF WEEK-2. A SLIGHT RISK (20-40% CHANCE) FOR PERIODS OF HEAVY
PRECIPITATION IS DESIGNATED FOR PORTIONS OF NORTHERN AND CENTRAL CALIFORNIA AND
WESTERN OREGON, OCT 30-NOV 3, WHERE THE GEFS, ECENS, AND CMCE PROBABILISTIC
EXTREMES TOOLS (PETS) INDICATE AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION
TOTALS EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY AND 0.75 TO 1 INCH. ECENS
INDICATES GREATER THAN 40% CHANCES FOR THESE THRESHOLDS ACROSS CENTRAL
CALIFORNIA. A SLIGHT RISK OF HEAVY SNOW IS MAINTAINED FOR THE KLAMATH AND
SIERRA MOUNTAIN RANGES OF CALIFORNIA FOR THE SAME VALID PERIOD WHERE
UNCALIBRATED MODEL GUIDANCE INDICATES 3-DAY SNOWFALL TOTALS REACHING OR
EXCEEDING 4 INCHES (6 INCHES LOCALLY).
ENHANCED MOIST FLOW IN ADDITION TO POSSIBLE TROPICAL MOISTURE FROM THE EASTERN
PACIFIC WHICH HAS BEEN VERY ACTIVE THIS SEASON, SUPPORTS CONTINUED ENHANCED
RISK OF HEAVY PRECIPITATION FOR PARTS OF THE SOUTHWESTERN CONUS. A MODERATE
RISK (40-60% CHANCE) OF HEAVY PRECIPITATION IS DELINEATED FOR PARTS OF ARIZONA,
OCT 30-NOV 1, WHERE PETS INDICATE AT LEAST A 30-40% CHANCE OF 3-DAY ACCUMULATED
PRECIPITATION EXCEEDS THE 85TH PERCENTILE AND 0.5 INCHES, FURTHER SUPPORTED BY
UNCALIBRATED GUIDANCE. A BROADER AREA OF SLIGHT RISK (20-40% CHANCE) OF HEAVY
PRECIPITATION IS HIGHLIGHTED ACROSS SOUTHERN PORTIONS OF THE FOUR CORNERS AND
WESTERN TEXAS FOR THE SAME PERIOD. LOCALIZED FLOODING IS POSSIBLE IN THESE
AREAS, BUT A BRIEF RESPITE OF POSSIBLE FLOODING IS ANTICIPATED BY END OF WEEK-1
HEADING INTO WEEK-2 SO NO FLOODING HAZARD IS DESIGNATED AT THIS TIME. FURTHER
NORTH, A SLIGHT RISK OF PERIODIC HEAVY SNOW IS POSTED FOR PARTS OF THE
NORTHERN AND CENTRAL ROCKIES OCT 30-NOV 3. SOME AREAS MAY RECEIVE GREATER THAN
4 INCHES OF SNOWFALL IN A 3-DAY PERIOD.
SURFACE HIGH PRESSURE OVER THE EASTERN CORN BELT AND MID-ATLANTIC, AND A
DEVELOPING STORM SYSTEM OFF THE SOUTHEAST COAST AND FRONT FURTHER NORTH, ARE
EXPECTED TO RESULT IN A STRENGTHENING OF THE REGIONAL PRESSURE GRADIENT,
RESULTING IN INCREASED LIKELIHOOD OF HIGH WINDS ACROSS PARTS OF THE EAST COAST.
A BROAD AREA IS HIGHLIGHTED ACROSS MUCH OF THE EAST COAST WITH A SLIGHT RISK OF
HIGH WINDS DUE TO UNCERTAINTY OF WHERE ENHANCED WINDS ARE MOST LIKELY, OCT
28-30. ENSEMBLES INDICATE INCREASED POTENTIAL FOR 10 M WIND GUSTS EXCEEDING 20
KNOTS (ABOUT 23 MPH) ACROSS THE RISK AREA.
DURING THE SECOND HALF OF WEEK-2, SURFACE HIGH PRESSURE MOVING OFF THE
MID-ATLANTIC COAST SUPPORTS AN INCREASE IN MOIST, SOUTHERLY FLOW FROM THE
WESTERN GULF NORTHWARD ACROSS MUCH OF THE LOWER MISSISSIPPI VALLEY AND EASTERN
SOUTHERN PLAINS. A SLIGHT RISK OF EPISODIC HEAVY PRECIPITATION IS POSTED FOR
PARTS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHERN PLAINS, OCT 30-NOV 3 WHERE
THERE IS GOOD AGREEMENT AMONG THE PETS INDICATING AT LEAST A 20% CHANCE OF
3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND 1 INCH.
MID-LEVEL TROUGHING IS FORECAST TO DEVELOP OFF THE WEST COAST OF MAINLAND
ALASKA, ALONG WITH A SERIES OF POSSIBLY STRONG STORMS TRACKING ACROSS THE
BERING SEA AT THE BEGINNING OF WEEK-2. THESE STORMS MAY RESULT IN EPISODIC HIGH
WINDS FOR WESTERN PORTIONS OF ALASKA. A MODERATE RISK OF HIGH WINDS IS
DESIGNATED FOR PARTS OF WESTERN ALASKA, OCT 28-30, WHERE THE ECENS (GEFS)
INDICATES AT LEAST A 40% (30%) CHANCE OF WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE AND 40 MPH, FURTHER SUPPORTED BY ENSEMBLE GUIDANCE SHOWING ENHANCED
CHANCES OF WIND GUSTS EXCEEDING THESE VALUES. A BROADER AREA IS HIGHLIGHTED
WITH A SLIGHT RISK (GREATER THAN 20% CHANCE) OF HIGH WINDS ACROSS PARTS OF
WESTERN ALASKA, THE ALASKA PENINSULA, AND ALEUTIANS FOR THE SAME DURATION.
ANTICIPATED STRONG LOW-LEVEL WESTERLY WIND ANOMALIES BRANCHING OFF FROM THE
TROPICS, EASTWARD UP THROUGH HAWAII MAY BRING ENHANCED MOISTURE TO THE STATE.
ADDITIONALLY, A SERIES OF SURFACE LOWS APPROACHING OR OVER HAWAII MAY LEAD TO
INCREASED LIKELIHOOD OF ENHANCED RAINFALL ACROSS SOME PARTS OF HAWAII DURING
WEEK-2.
FORECASTER: MELISSA OU
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page