371
FXUS21 KWNC 281915
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT October 28 2026

SYNOPSIS: An area of mid-level low pressure approaching the West Coast is
predicted to bring periods of heavy precipitation, high elevation snow, and
high winds across parts of Northern California through the Pacific Northwest.
Another area of low pressure is forecast to move across the Atlantic coast
states early in week-2, bringing increased chances for heavy precipitation and
high winds to much of this region.

HAZARDS

Slight risk of heavy precipitation for portions of the Pacific Northwest and
northwestern California, Sat-Wed, Nov 7-11.

Slight risk of heavy snow for the Cascades and Klamath Ranges, Sat-Wed, Nov
7-11.

Slight risk of high winds for coastal portions of the Pacific Northwest, and
the northwestern California coast, Sat-Wed, Nov 7-11.

Slight risk of heavy precipitation for most of the East Coast states, Thu, Nov
5.

Slight risk of high winds for the Lower Great Lakes region, Ohio Valley,
central and northern Appalachians, Northeast, and Upper Mid-Atlantic, Thu, Nov
5.

DETAILED SUMMARY

FOR SATURDAY OCTOBER 31 - WEDNESDAY NOVEMBER 04:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY NOVEMBER 05 - WEDNESDAY NOVEMBER 11: A mid-level trough is
forecast to progress from the southeastern Bering Sea into the Gulf of Alaska
during the first few days of week-2. Negative height departures in the ensemble
mean runs surpass 180 meters for most of the week-2 period. A corresponding
area of surface low pressure is predicted beneath the mid-level trough. This
sets up the potential for a long duration atmospheric river event for the
Pacific Northwest and Northern California.



Probabilistic Extremes Tools (PETs) from the GEFS and ECENS ensemble means and
uncalibrated precipitation tools, as well as the Integrated Water Vapor
Transport (IVT) tools indicate much of the moisture associated with the
mid-level trough over the northeast Pacific is passing north of 50N latitude,
moving into British Columbia. South of 50N, there is considerably less
precipitation forecast across the Pacific Northwest and northern portions of
California, which is why the regional moderate risks depicted for the past
several days for heavy precipitation and heavy snow were discontinued today.
Nevertheless, a slight risk of heavy precipitation is still indicated for those
areas, valid Nov 7-11, as onshore flow becomes established. Liquid equivalent
3-day precipitation amounts are indicated by the PETs to be 1.0-1.5 inches, and
greater than the 85th historical percentile. Farther inland, there is a slight
risk of heavy snow for the highest elevations of the Cascades and Klamath
Ranges, valid for the same period. Along the coast, from northwestern
California to the Olympic Peninsula, a slight risk of high winds is posted,
also valid Nov 7-11, coincident with an increased pressure gradient as the
mid-level low approaches from the Pacific. Coastal wind speeds are forecast to
exceed the 85th percentile and at least 34 knots, based on the wind PETs and
the 0z ECENS 10-meter wind speed gusts.



An occluded low pressure system is forecast to move across the Atlantic coast
on day 8, and then offshore on day 9.  A slight chance of heavy precipitation
is posted in advance of the associated cold front, which includes most of the
East Coast states, on Nov 5. Amounts of at least an inch and greater than the
85th percentile are favored by the PETs and uncalibrated precipitation tools.
Though conditions have been fairly dry across much of the Atlantic coastal
plain during the last 30 days, there is still the chance of localized urban
flooding with the passage of this occluded system. A slight risk of high winds
is delineated across most of the Lower Great Lakes region, Northeast, and upper
Mid-Atlantic, Nov 5. This is broadly associated with the mid-level dynamics and
area of surface low pressure associated with this storm system and the expected
areas of enhanced pressure gradients.



In southwestern Alaska, much above normal temperatures are forecast in week-2,
which is likely to bring air temperatures above 32 deg F. This may delay
ongoing river freezing. Residents are advised to be wary of very thin ice on
shallow bodies of water. Apart from this, there are no temperature,
precipitation, or wind hazards posted for Alaska at this time.

FORECASTER: Anthony Artusa

$$