…Another round of heavy lower elevation/coastal rain and high elevation
mountain snow returns to the Pacific Northwest Christmas Day…
…A couple rounds of showers and thunderstorms in the south-central
states through Thursday…
…Relatively mild, average to above average conditions across the
majority of the country Christmas day…
It will be a tale of two weather patterns for the country heading through
the Christmas holiday, as portions of the West and south-central U.S. see
a couple rounds of unsettled weather while most other locations remain
dry. In the West, moderate to heavy lower elevation rain will remain
possible with showers and thunderstorms in California though Christmas Eve
as a Pacific system moves inland, with heavy higher elevation snow for the
Sierra. Some isolated flooding will remain possible along upslope regions
of the Sierra. The precipitation focus will spread inland over the Great
Basin and northern/central Rockies through Christmas Eve night and into
Christmas morning as the system continues eastward, with a mix of rain and
snow for lower elevations and snow into the mountains. Any accumulations
should light for lower elevations with a few inches possible in the
mountains. Another Pacific system will approach the Pacific
Northwest/northern California on Christmas day bringing another round of
moderate to heavy lower elevation/coastal rain and heavy high elevation
snow. Some isolated flooding will be possible along upslope regions of the
coastal ranges, and Winter Storm Watches have been issued for the Cascades
south through the Mt. Shasta region in California for snow totals of 1-2
feet through Thursday. The system will continue inland into the day
Thursday bringing more lower elevation rain/snow and high elevation snow
to the Great Basin and northern/central Rocky Mountains. Heavy snow totals
of 4-8 inches, locally 12″+, are also expected through many ranges of the
northern Great Basin/Rockies. Any accumulations at lower elevations should
remain light. Strong, gusty winds will spread inland with the system and
lead to blowing snow at higher elevations.
To the east, showers and thunderstorms remain in the forecast for portions
of the south-central U.S. the next couple of days as a couple upper level
waves/surface systems pass through the region. Showers and thunderstorms
will continue through this evening over eastern Texas and into the
ArkLaTex ahead of the first system. Some severe thunderstorms producing
mainly hail and isolated damaging winds are possible, as well as some
locally heavy downpours and isolated instances of flash flooding. This
system will make little progress eastward and weaken Christmas day as a
supporting upper-level wave departs the region, which fortunately means
more scattered chances of storms into the Middle/Lower Mississippi Valley.
Then, by early Thursday, another upper-level wave dropping southward will
lead to lee cyclogenesis and a second frontal system pushing eastward into
the southern Plains. Plentiful Gulf moisture lingering just along the
coast will quickly return back northward over Texas/Oklahoma and into the
Arklatex, leading to a renewed round of showers and thunderstorms. Severe
weather will once again be possible with a Slight Risk (level 2/5) issued
from the Storm Prediction Center for the threat of damaging winds as well
as the potential for tornadoes. In addition, widespread storms producing
locally heavy downpours will also once again bring the threat of some
isolated flash flooding. Some more scattered showers and storms will be
possible further northeastward into the Middle and Upper Mississippi
Valleys as well.
Elsewhere, some lingering showers will be possible this evening along the
coastal Carolinas. Scattered showers and thunderstorms will be possible
across Florida through Christmas day and into Thursday. Conditions will
generally be at or above average temperatures-wise through Christmas, with
some of the higher anomalies of 5-15 degrees most likely for the central
U.S. Forecast highs Christmas Day and Thursday generally range from the
30s and 40s for the northern Rockies/Plains east through the Great Lakes
and New England/Mid-Atlantic; the 40s and 50s for the Pacific
Northwest/northern California east through the Great Basin, central
Rockies/Plains, and the Middle Mississippi and Ohio Valleys; the 50s and
60s in the Southeast; and the 60s and 70s for southern California, the
Desert Southwest, Texas, and Florida.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php