218
FXUS21 KWNC 091911
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 09 2025

SYNOPSIS: Mid-level low pressure is forecast along or near the West Coast as
week-2 gets underway, eventually moving eastward and deamplifying by the middle
of Week-2. This brings slight risks of hazardous precipitation, snow, and wind
to several areas from the Southwest and the Sierra Nevada through the Rockies.
Surface low pressure is expected to develop in the southern High Plains early
week-2 and move eastward, bringing increased chances for heavy precipitation to
portions of the south-central and southeastern Conterminous U.S. (CONUS) and
potentially abetting high winds in part of the central CONUS. Stormy weather is
possible at times throughout southern Alaska November 17-23, but precipitation
and winds are likely to remain below hazardous thresholds.

HAZARDS

Slight risk of heavy precipitation for much of the Southwest and southern
Rockies, Mon-Wed, Nov 17-19.

Slight risk of heavy precipitation for much of the Tennessee, Lower and Middle
Mississippi, and Lower Ohio Valleys, and adjacent areas of the Great Plains and
Southeast, Tue-Thu, Nov 18-20.

Slight risk of heavy snow over the Sierra Nevada and much of the Great Basin
and Rockies, Mon-Wed, Nov 17-19.

Slight risk of high winds from the Rockies through much of the Great Plains and
parts of the adjacent Mississippi Valley, Mon-Wed, Nov 17-19.

DETAILED SUMMARY

FOR WEDNESDAY NOVEMBER 12 - SUNDAY NOVEMBER 16:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY NOVEMBER 17 - SUNDAY NOVEMBER 23: A mid-level trough is forecast to
move into the West at the start of the period, continuing a period of active
weather across the West. The GEFS and CMCE continue to predict a deep trough
supporting increased chances of heavy precipitation across portions of the
West, and the ECENS mean has moved in this direction relative to its weaker
depiction yesterday. There is a bit of a disconnect between the dynamical
models and the ensemble means today, with the dynamical models showing two
distinct shortwaves in the West - one moving into the Northwest, and another
either moving through the Southwest or cutting off and drifting into the
adjacent Pacific Ocean. The ensemble means continue to favor a full latitude
trough moving into the west, but are focusing the largest negative height
anomalies on the southern side of this trough axis which is then held together
better in the southern reaches of the West rather than farther north, where it
gets sheared out. The Probabilistic Extremes Tools (PETs) from the ensembles,
in particular the ECENS, today focus the best odds for precipitation totals
over the 15th percentile over the Southwest and the southern Rockies during the
first few days of the period, removing the heavy precipitation and heavy snow
threats from the northwestern CONUS. The ECENS PET shows a 40 to 70 percent
chance that precipitation totals for the first 3 days of week-2 will exceed the
top 15th percentile, but the other PETs are considerably less robust. As a
result, only a slight risk of heavy precipitation is posted for the first few
days of week-2, and is restricted to the southern tier of the western CONUS.
The dynamical models and ensemble means further diverge from each other later
in the period, with some dynamical models showing another strong trough digging
into the western CONUS toward the end of week-2. The ensemble means bring some
mid-level troughing back toward or into the West by the end of the period, but
with considerably less amplitude and significant uncertainty regarding the
precise timing and location of such a feature. No hazards are posted in
association with the possible re-amplification of the mid-level trough in the
West at this time, but the situation will need to be monitored.



Despite the largest negative height anomalies settling into the Southwest and
southern Rockies for the first few days of the period, the GEFS PET snowfall
guidance continues to indicate enhanced probabilities for heavy snow in the
Sierra Nevada although probabilistic output from the GEFS and ECENS is
unimpressive. The dynamical models and ensemble mean raw snowfall totals are
not particularly consistent with the timing or location of heavy snow, but
consistent with the GEFS PET and the expected position and orientation of the
mid-level trough axis in the West, a slight risk of heavy snowfall is posted
for most of the Sierra Nevada, Great Basin, and higher elevations of the
Rockies for the first 3 days of week-2. Heavy snow may again become a threat
later week-2 if the dynamical models are more correct and a strong mid-level
trough digs into the West toward the end of the period, but the uncertainty
precludes posting any hazards in association with this potential development.



The southern end of the mid-level trough - or some portion of it - is expected
to drift toward the east and maintain at least moderate amplitude early week-2.
Southerly flow ahead of the trough should begin to tap Gulf moisture as it
proceeds eastward, increasing the odds for heavy precipitation across a
significant portion of the south-central and southeastern CONUS. Some raw model
output is fairly robust, dropping multiple inches of rain on parts of the
region, but all of the PETs keep probabilities for precipitation in the top 15%
of the historical envelope and exceeding an inch relatively low, under 40
percent in the ECENS PET and below 30 percent in the GEFS PET. As a result,
only a slight risk of heavy precipitation is posted for Nov 18-20 in the
region, but it should be noted that the raw output from a few of the models are
somewhat wetter than yesterday.



The eastward-moving mid-level trough may also trigger lee-side cyclogenesis in
the High Plains which eventually pulls off to the east-northeast. This in turn
increases the risk of high winds from the Rockies eastward through much of the
Great Plains and part of the Upper Mississippi Valley from November 17-19. The
ECENS PET shows odds for winds in the top 15th percentile of the historical
envelope exceeding 40 percent around November 19 in part of New Mexico, similar
to yesterday, and GEFS PET shows odds exceeding 30 percent in a few locations.
The risk ends toward mid-week as the mid-level trough and associated surface
low track east and weaken.



For Alaska, a mid-level trough may affect the state through the entirety of
week-2, supporting one or more strong low pressure systems in the Bering Sea
and Gulf of Alaska. This could lead to high winds and heavy precipitation
across the Aleutians and southern Alaska. This signal is slightly stronger in
the PETs than yesterday, but there remains a lot of inconsistency in the
guidance regarding the strength and evolution of the features involved, so
while this situation will need to be monitored, no hazard is posted at this
time.

FORECASTER: Rich Tinker

$$