165
FXUS21 KWNC 301912
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST January 30 2025

SYNOPSIS: Todays models are in better agreement compared to yesterday
regarding a more amplified mid-level pattern across the contiguous U.S. (CONUS)
during week-2, with a rebuilding of mid-level low pressure across the West and
mid-level high pressure downstream across the Eastern Seaboard. This evolution
favors a persistence of below-normal temperatures across portions of the
northwestern and north-central CONUS throughout the period, with the most
anomalous cold favored over the Pacific Northwest. Precipitation chances across
the Northwest are favored to diminish early in the period underneath surface
high pressure, but may again increase later in the period as the mid-level low
re-amplifies. The synoptic setup is favorable for a series of surface lows
across the East, but there is large model spread regarding the timing and
strength of any specific features. Therefore, broad slight risks of heavy
precipitation and heavy snow are posted across much of the East and the
Northern Tier respectively for all of week-2.

HAZARDS

High risk of much below normal temperatures across portions of northwestern
Oregon and western Washington, Fri, Feb 7.

Moderate risk of much below normal temperatures across portions of the Pacific
Northwest, Fri-Sun, Feb 7-9.

Slight risk of much below normal temperatures across portions of the
northwestern CONUS and extending into the Northern Rockies and Plains, Fri-Thu,
Feb 7-13.

Slight risk of heavy precipitation across much of the eastern CONUS, Fri-Thu,
Feb 7-13.

Slight risk of heavy snow across portions of the Northern Plains, Upper
Mississippi Valley, Great Lakes, and Northeast, Fri-Thu, Feb 7-13.

Slight risk of high winds across portions of southern California, Fri-Sun, Feb
7-9.

DETAILED SUMMARY

FOR SUNDAY FEBRUARY 02 - THURSDAY FEBRUARY 06:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY FEBRUARY 07 - THURSDAY FEBRUARY 13: Troughing is forecast across the
northwestern CONUS during week-2 resulting in below-normal temperatures along
the West Coast and into parts of the north-central CONUS. The most anomalous
cold is predicted to be across the Pacific Northwest, where the ECENS and GEFS
Probabilistic Extremes Tools (PETs) depict probabilities of at least 60 percent
for minimum temperatures falling below the 15th climatological percentile.
While colder temperatures appear more likely later in week-1, the continuing
downward trend in temperatures in the guidance, along with the PETs, supports a
high risk for much below normal temperatures across the Portland, OR and
Seattle, WA metro areas on day-8 (Feb 7) where overnight temperatures may fall
into the mid 20s deg F. The ECENS, GEFS, and CMCE are more bullish at
re-amplifying troughing over the West toward the middle and later portion of
week-2. Therefore, anomalously cold temperatures are now favored to continue
throughout week-2 supporting an extension of the moderate risk through day-10
(Feb 9) and the slight risk for the entire period. The slight risk area
includes portions of the Northern Rockies, Northern Plains, and Upper
Mississippi Valley where subzero temperatures are possible. While these
temperatures are considerably colder compared to the coastal Pacific Northwest,
it is less certain if apparent temperatures will reach the very cold criteria
across the north-central CONUS, justifying only a slight risk.



Precipitation signals in the uncalibrated 0z ECENS and GEFS diminish at the
outset of week-2 compared to the week-1 period as surface high pressure pushes
across the Northwest. There could still be episodes of enhanced onshore flow,
especially around the middle of the period, and wintry precipitation cannot be
ruled out even over low elevation areas. However, there is now too much
uncertainty in the ensembles, and the GEFS snow water equivalent (SWE) PET
depicts probabilities below 20 percent for SWE to reach the 85th climatological
percentile early in the period. Therefore, the related heavy snow hazard across
the West has been discontinued.



The troughing over the western CONUS and ridging along the Eastern Seaboard
favors an enhanced baroclinic zone over the east-central CONUS, and multiple
areas of surface low pressure to track across the region. However,
deterministic solutions from the GFS and ECMWF vary regarding tracks and
impacts, and the ensembles do not appear to key in on any specific feature.
Given the favorable set-up, a broad slight risk of heavy precipitation is
posted across much of the eastern CONUS for all of week-2. While model and
analog guidance support enhanced probabilities for above-normal precipitation
across the Ohio and Tennessee Valleys during the period, the lack of confidence
regarding timing of any one specific system precludes designating a moderate
risk. There is some enhanced risk of flooding across parts of the Mississippi
and Ohio Valleys dependent on storm track. Wintry weather is also possible on
the northern side of the low tracks, and a broad slight risk for heavy snow is
posted across portions of the Northern Plains, Upper Mississippi Valley, Great
Lakes, and Northeast for the entire period.



Offshore flow is favored to increase across southern California early in the
period as surface high pressure moves by to the north. While signals for
hazardous winds are modest at best in the guidance, there is high sensitivity
in the region due to recent and ongoing wildfires. Therefore, a slight risk for
high winds is highlighted Feb 7-9.



Ridging is forecast over Alaska during week-2 favoring relatively warmer
temperatures over much of the Mainland and Aleutians compared to week-1.
Below-normal temperatures remain forecast across Southeast Alaska, but hazards
thresholds are unlikely to be reached. Below-normal precipitation is also
predicted over much of southern Alaska, with ridging pushing higher chances of
precipitation further to the north across the western and northern Mainland.

FORECASTER: Thomas Collow

$$