452
FXUS21 KWNC 151918
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT October 15 2025

SYNOPSIS: Strong low pressure at the surface and mid-levels is favored to shift
from the Bering Sea into the Gulf of Alaska early in week-2, bringing with it
potentially hazardous winds and precipitation into the Pacific Northwest
throughout the forecast period. Widespread surface high pressure east of the
Rockies throughout the forecast period decreases the potential for widespread
hazardous weather for most of the Contiguous U.S. (CONUS), although a strong
pressure gradient near the margin with the surface low over the Pacific
Northwest favors enhanced wind speeds for portions of the Northern and Central
Rockies and Northern Plains.

HAZARDS

Moderate risk of heavy precipitation for western portions of Washington and
Oregon, Thu-Mon, Oct 23-27.

Moderate risk of heavy snow for the Cascade Mountains, Thu-Mon, Oct 23-27.

Moderate risk of high winds for the Washington and Oregon coasts as far south
as Cape Blanco, Thu-Mon, Oct 23-27.

Slight risk of heavy precipitation for much of Washington and Oregon as well as
Northern California, Thu-Mon, Oct 23-27.

Slight risk of heavy snow for the Cascades, Northern Sierras, and northern
Klamath mountains, Thu-Wed, Oct 23-29.

Slight risk of high winds from Cape Mendocino north to Puget Sound, Thu-Wed,
Oct 23-29.

Slight risk of high winds for portions of the Northern and Central Rockies and
much of the Northern Plains, Thu-Wed, Oct 23-29.

Slight risk of snow heavy for the Northern Rockies as well as the Uinta and
northern Wasatch Mountains, Sat-Wed, Oct 25-29.

Slight risk of high winds for the Alaskan Peninsula and Aleutian Islands,
Thu-Fri, Oct 23-24.



DETAILED SUMMARY

FOR SATURDAY OCTOBER 18 - WEDNESDAY OCTOBER 22:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY OCTOBER 23 - WEDNESDAY OCTOBER 29:
Todays model solutions continue to depict a strong mid-level trough and associa
ted surface low pressure over the Gulf of Alaska at the outset of week-2. These
features are favored to persist and remain quite amplified throughout the foreca
st period, potentially bringing high winds to western Alaska early in week-2 and
 heavy precipitation, snow, and wind to the Pacific Northwest throughout week-2.
 Ensemble means for the surface low pressure center get as low as 980 hPa in the
 ECENS, and both the GEFS and ECENS are in very good agreement on the strength a
nd evolution of this significant system. High winds continue to be a lingering c
oncern with this system for Alaska. A deep surface low over the Gulf of Alaska a
nd very tight pressure gradients are depicted by multiple models over the Bering
 Sea, potentially leading to the development of gap winds along the Alaskan Peni
nsula and Aleutian Islands as well as enhanced winds through the Bering Strait e
arly in week-2., Therefore a slight risk of high winds is posted for these areas
 for Oct 23-24.



In addition to a deep trough at the surface and aloft over th
e Gulf of Alaska, models depict an interaction with a long plume of enhanced atm
ospheric moisture streaming in from the North Pacific, resulting in potentially
hazardous precipitation for much of the Pacific Northwest in addition to high wi
nds associated with continued tight pressure gradients along the coast. The Inte
grated Vapor Transport (IVT) tool has shown a steady stream of vapor fluxes exce
eding 250 kg/(ms) streaming into the Pacific Northwest for several model cycles.
 Uncalibrated probabilities from the GEFS and ECENS show chances of at least 40%
 of 3-day precipitation totals  exceeding 2 inches through the middle of week-2
for the Pacific Northwest, while both the GEFS and ECMWF PETs indicate at least
a 20% chance of three-day precipitation exceeding the 85th percentile for a broa
der area across the northwestern CONUS throughout the forecast period. Model gui
dance is showing increasing signals regarding the potential for heavy snow as we
ll, with ensemble mean snowfall accumulation for week-2 meeting or exceeding 2 f
eet for the Cascades, with lower but still significant accumulations further sou
th along the Sierras and across the Northern Rockies. Across variables and model
s, there is excellent agreement among the available guidance concerning this dev
eloping system, raising forecast confidence particularly with regard to the inte
nsity of potential impacts. The GEFS and ECMWF disagree slightly with respect to
 timing, with the ECMWF a little slower to develop more impactful weather. Despi
te this disagreement, given the synoptic pattern and consistent indications of a
 potent developing system, hazards are designated for the northwestern CONUS pri
marily based on the more bullish ECMWF solution. A moderate risk of heavy precip
itation is posted for western Washington and Oregon, as well as a moderate risk
of high winds designated for coastal Washington and Oregon south to Cape Blanco,
 and a moderate risk of heavy snow for the Cascade Mountains, all covering the p
eriod Oct 23-27. A slight risk of heavy precipitation is posted for much of Wash
ington, Oregon, and Northern California, with a slight risk of heavy snow highli
ghted over the Cascades, Northern Sierras, and Northern Klamath Mountains, and a
 slight risk of high winds for coastal portions of Washington, Oregon, and Calif
ornia south to Cape Mendocino, all covering the entire week-2 period. Finally, w
hile no flooding possible hazard is issued at this time, due to anticipated larg
e precipitation totals are likely to increase river and stream levels for the re
gion and may result in localized minor flooding.



As strong moist onshore flow
 persists, the chance for heavy snow is favored to move into the Interior West.
Uncalibrated probabilities from the ECENS and GEFS both indicate at least a 20%
chance of three-day snow accumulations exceeding 6 inches during the middle to e
nd of week-2 for the Northern Rockies as well as the northern mountains of Utah.
 Therefore a slight risk of heavy snow is posted for these regions for Oct 25-29
. A slight risk of high wind is designated for the Northern Rockies and much of
the Northern Plains throughout the forecast period, where the periphery of the i
ncoming surface low pressure is anticipated to form another zone of tight gradie
nts with surface high pressure dominating most of the rest of the CONUS througho
ut the forecast period.

FORECASTER: Danny Barandiaran

$$