874
FXUS21 KWNC 121902
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST November 12 2025

SYNOPSIS: Dynamical models continue to favor an active pattern heading into
next week. Forecast mid-level low pressure is expected to bring an increased
risk of heavy precipitation, high elevation snow, and periods of high winds
across many parts of the Interior West. Surface low formation in the lee of
Rockies with ample moisture from the Gulf supports elevated chances for heavy
precipitation and periods of high winds over the southcentral and southeastern
contiguous U.S. early in week-2. Mid-level low pressure centered over the
Bering Strait and associated surface low development may lead to locally heavy
precipitation and high winds over parts of the Alaska Mainland and the
Southeast.

HAZARDS

Moderate risk of heavy precipitation for parts of the Southern Plains, Lower
and Middle Mississippi, Tennessee, and Ohio Valleys, and the Southeast, Thu,
Nov 20.

Slight risk of heavy precipitation for much of the Great Plains, Mississippi,
Tennessee and Ohio Valleys, Appalachians, and Southeast, Thu-Sun, Nov 20-23.

Slight risk of high winds for parts of the Southern and Central Plains and
Middle and Lower Mississippi, Tennessee and Ohio Valleys, Thu-Sat, Nov 20-22.

Slight risk of heavy precipitation for parts of the Southwest and southern
Rockies, Thu-Fri, Nov 20-21.

Slight risk of heavy snow over much of the Rockies and Great Basin, Thu-Wed,
Nov 20-26.

Slight risk of high winds for many parts of the western and central CONUS,
Thu-Wed, Nov 20-26.

Slight risk of high winds for parts of the Aleutians, southern and western
Mainland, and Southeast Alaska, Thu-Fri, Nov 20-21.

DETAILED SUMMARY

FOR SATURDAY NOVEMBER 15 - WEDNESDAY NOVEMBER 19:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY NOVEMBER 20 - WEDNESDAY NOVEMBER 26: Consistent with previous
ensemble mean guidance, the GEFS and ECMWF are at odds with one another in
regards to the 500-hPa height pattern over the western CONUS towards the middle
of next week. While both models feature a highly amplified blocking ridge
center near Greenland, the ECMWF favors deeper troughing over the Interior
West, with more shortwave energy shifting inland over the Pacific Northwest
that is absent in the GEFS. As the period progresses, however, the evolving
mean mid-level pattern does become better aligned between these models, as both
feature the development of a high latitude amplifying ridge over Alaska and the
northeastern Pacific. Such a pattern shift would yield to more persistent
troughing downstream over the West, with the potential for much colder
temperatures overspreading the northwestern and northcentral CONUS later in
November.



Despite the aforementioned model differences next week, much of the troughing
across the West is expected to induce surface low development in the lee of the
Southern Rockies, where there continues to be good model support for enhanced
and potentially heavy precipitation over the south-central CONUS. Based on raw
precipitation and Probabilistic Extreme Tool (PET) guidance which show greater
than 40% (20%) chances for amounts exceeding an inch (two inches), a moderate
risk of heavy precipitation remains posted over the Southern Plains eastward to
the Tennessee Valley and remains valid through Nov 20. Relative to yesterday,
coverage for this moderate risk area is expanded northeastward into the Middle
Mississippi, and Ohio Valley due to greater chances of precipitation exceedance
in these tools early in the period. A broader slight risk area for heavy
precipitation remains posted where probabilities for amounts exceeding an inch
are less than 40%, with the valid times extended through day 11 (Nov 23) due to
the potential for additional surface low development in the lee of the Rockies
with enhanced precipitation amounts favored later in week-2. This potential is
supported in both the GEFS and ECMWF Probabilistic Extremes Tools (PETs) which
maintain at least 20% chances for precipitation amounts exceeding the 85th
percentile through the middle of week-2. Due to increasing wind signals in both
the GEFS and ECMWF PETS likely associated with the deepening mean low, a slight
risk of high winds is issued for portions of the Plains, Mississippi, Tennessee
and Ohio Valleys for Nov 20-22. On the backside of the mean surface low, it is
worth noting that accumulating snowfall is possible over the lower elevations
of Great Plains, though amounts are expected to remain below hazard thresholds.



Following the shortwave disturbance that is favored to propagate across the
Pacific Northwest by the middle of next week, the ECMWF has abruptly backed off
on any renewal of enhanced onshore flow later next week in the latest ensemble
run. This is reflected in the latest Integrated Vapor Transport (IVT) tools,
where there is better agreement between the GEFS and ECMWF depicting more muted
signals tied to the building heights favored. Combined with lesser totals in
raw and calibrated precipitation tools, the slight risk of heavy precipitation
and high elevation heavy snow is discontinued in the updated outlook. However,
an amplifying longwave ridge over the northeastern Pacific and into Alaska
supports the potential for an arctic air outbreak over the northwestern and
possibly reaching the northcentral CONUS later in week-2. A colder temperature
response is depicted in the ECMWF and Canadian PETs with increased signals in
percentile space for minimum temperatures falling below the 15th percentile
during the back half of week-2. Given general uncertainty at this lead and
little support for actual temperatures reaching hazards criteria, no
corresponding temperature shapes are issued, though this potential will
continue to be monitored in upcoming outlooks.



Tied to the amplified troughing favored over the Interior West, a slight risk
of heavy precipitation remains issued over the lower Four Corners region where
PETs continue to show increased chances for amounts exceeding the 85th
percentile and 0.5 inches. The risk area is extended through day 9 (Nov 21) due
to another round of precipitation early in the period following a wet week-1.
Expansion of this slight risk area into southern California was considered
based on the ECMWF PET which depicts 20% chances for amounts exceeding an inch,
however this is less supported in its uncalibrated counterpart as well as the
drier GEFS.  With more persistent troughing over the Interior West, a slight
risk of high elevation heavy snow also remains posted for the higher elevations
of the Rockies and Great Basin and is extended through the entirety of week-2
which is supported in the raw ECMWF probabilistic snowfall guidance and the
GEFS Snow Water Equivalent PET. Similarly, a slight risk of high winds is also
extended through Nov 23 near the base and ahead of the mean troughing aloft.



Over Alaska, an amplified 500-hPa trough centered over the Bering Strait is
expected to lead to potential strong surface low development and possibly bring
periods of high winds and heavy precipitation to many parts of southern Alaska.
While there is still some uncertainty as to whether realized amounts exceed
hazard thresholds early in week-2, the mid-level and surface pattern supports
the continuation of a slight risk of high winds, and remains valid through Nov
21 before the troughing aloft is favored to deamplify.

FORECASTER: Nick Novella

$$