846
FXUS21 KWNC 181848
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 18 2025
SYNOPSIS: MODEL ENSEMBLES FAVOR A TRANSITION FROM AN AMPLIFIED WAVE TRAIN IN
MID-LEVEL PRESSURE TO A MORE FLATTENED PATTERN, RESULTING IN FEW CONCERNS FROM
A HAZARDOUS WEATHER PERSPECTIVE. EARLY IN WEEK-2 MID-LEVEL LOW PRESSURE OVER
THE NORTH PACIFIC MAY ENHANCE SURFACE WINDS ALONG PORTIONS OF THE CALIFORNIA
COAST.
HAZARDS
SLIGHT RISK OF EPISODIC HIGH WINDS FOR COASTAL PORTIONS OF CALIFORNIA SOUTH OF
POINT MENDOCINO, FRI-SAT, SEP 26-28.
DETAILED SUMMARY
FOR SUNDAY SEPTEMBER 21 - THURSDAY SEPTEMBER 25:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY SEPTEMBER 26 - THURSDAY OCTOBER 02: TODAY’S MODEL SOLUTIONS FOR
500-HPA HEIGHTS INDICATE A TRANSITION AWAY FROM AN AMPLIFIED WAVE TRAIN
STRETCHING OVER NORTH AMERICA TO A MUCH MORE ZONAL PATTERN DURING THE WEEK-2
PERIOD, RESULTING IN RELATIVELY TRANQUIL WEATHER WITH FEW CONCERNS WITH RESPECT
TO THE POTENTIAL FOR HAZARDOUS WEATHER OVER THE CONTIGUOUS U.S. (CONUS). AT THE
OUTSET OF WEEK-2 GUIDANCE CONTINUES TO DEPICT A FAIRLY DEEP TROUGH OFF THE WEST
COAST. THIS PATTERN, IN ADDITION TO PREDICTED SURFACE HIGH PRESSURE NEAR THE
WEST COAST AND ADJACENT SURFACE LOW PRESSURE OVER WEST COAST STATES, MAY RESULT
IN A TIGHT PRESSURE GRADIENT AT THE SURFACE AND INCREASED LIKELIHOOD FOR HIGH
WINDS ACROSS THE WEST COAST. A SLIGHT RISK OF EPISODIC HIGH WINDS IS
HIGHLIGHTED FOR COASTAL PORTIONS OF CALIFORNIA SOUTH OF POINT MENDOCINO FOR SEP
26-28, WHERE PROBABILISTIC EXTREME TOOLS (PETS) INDICATE AT LEAST A 20% CHANCE
OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND 25 MPH AND ENSEMBLE MEAN WIND
SPEED FROM BOTH THE GEFS AND ECMWF INDICATE ENHANCED WINDS FOR MUCH OF THE
CALIFORNIA COAST EARLY IN WEEK-2.
IN ADDITION TO ENHANCED WINDS, MODELS DEPICT SIGNIFICANT MOISTURE TRANSPORT
INTO THE PACIFIC NORTHWEST AS THIS TROUGH MOVES INTO THE INTERIOR WEST. THIS IS
LIKELY TO RESULT IN PERIODS OF ENHANCED PRECIPITATION FOR MUCH OF THE
NORTHWESTERN CONUS THROUGH THE MIDDLE OF WEEK-2. WHILE LOW ELEVATION
ACCUMULATIONS (I.E. RAIN) ARE NOT LIKELY TO REACH HAZARDOUS THRESHOLDS, THERE
IS AN INCREASED LIKELIHOOD OF HEAVY SNOW ACROSS HIGH ELEVATION AREAS OF THE
NORTHERN CASCADES AND ROCKIES AS A COLDER AIRMASS MOVES IN WITH THE TROUGH,
POTENTIALLY DROPPING TEMPERATURES SUFFICIENTLY TO ALLOW FOR SNOW IN THE
MOUNTAINS. WHILE INDICATED SNOW ACCUMULATIONS ARE NOT PARTICULARLY LARGE, THIS
WOULD BE UNUSUALLY EARLY TO RECEIVE THE FIRST SIGNIFICANT SNOWS OF THE SEASON
FOR THE REGION. TODAY’S MODEL SOLUTIONS ARE LESS BULLISH WITH REGARD TO
SUFFICIENTLY LOW TEMPERATURES FOR SNOW, THEREFORE THE SLIGHT RISK OF HEAVY SNOW
FOR THE CASCADES AND PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES HAS BEEN
REMOVED FROM TODAY’S OUTLOOK. SNOW ACCUMULATIONS STILL REMAIN A POSSIBILITY AT
VERY HIGH ELEVATIONS AND GIVEN THE EARLY TIMING FOR MOUNTAIN SNOW POTENTIAL
THIS SITUATION WILL BE MONITORED CLOSELY IN THE COMING DAYS.
FORECASTER: DANNY BARANDIARAN
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