…Unsettled weather to persist across the Northwest U.S. through the
middle of the week much colder temperatures and heavy snowfall across the
Cascades and the northern Rockies…
…An atmospheric river will continue to stream across northern and
central California over the next couple of days with additional heavy
rains and concerns for flooding…
…New storm system to bring a threat for light snow, sleet and freezing
rain to portions of the Ohio Valley and the Mid-Atlantic region by
Thursday…
…Record high temperatures are expected across much of the Southern U.S.
over the next few days…
A persistent deep layer low center and associated trough axis will
continue to impact the Pacific Northwest and the northern Rockies going
through the middle of the week which will continue to support widespread
unsettled weather. Moist onshore flow into the higher terrain coupled with
colder temperatures continuing to settle south from southwest Canada will
maintain a threat for locally heavy snowfall across the Cascades and the
snow levels will be low enough to support heavy snowfall also for the
coastal ranges and some of lower elevations given the depth of cold air
that will be in place. Heavy snowfall is also expected to continue farther
inland into the interior mountain ranges such as the Sawtooth,
Bitterroots, Tetons and Absaroka Range. Much of this snowfall will be
connected to the persistent and strong atmospheric river that will
continue to impact central and northern California over the next couple of
days. Additional snowfall accumulations of 1 to 2 feet will be possible
over the Cascades and the northern Rockies with locally heavier totals
through early Thursday.
The aforementioned atmospheric river impacting California will only
gradually settle southward through the middle of the week as multiple
waves of low pressure traverse the front and bring strong Pacific moisture
transport into the coastal ranges, portions of the Central Valley, and the
foothills of the Sierra Nevada. This will result in more heavy rain for
the region with concerns for flooding which will also include the Bay
Area. An additional 2 to 4 inches of rain is expected for the coastal
ranges, with 3 to 6+ inches for the Sierra Nevada foothills. The Weather
Prediction Center has maintained a Slight Risk (level 2 of 4) of excessive
rainfall across the region to account for this. Meanwhile, for the highest
elevations of the central and northern Sierra Nevada, as much as 1 to 3
feet of new snowfall is expected.
Farther off to the east, the story going through today and Wednesday will
be Arctic high pressure nosing southward across the northern Plains and
Midwest, with this airmass in a moderating fashion gradually pushing east
across the Great Lakes region and Northeast in behind a cold front. This
cold air will be in place though ahead of a new storm system approaching
the Ohio Valley and Mid-Atlantic region by Wednesday night and Thursday
which is expected to drive a concern for some light snowfall, but also a
swath of sleet and freezing rain. Hazardous winter weather driving
conditions are expected across these areas.
Temperatures across the Northwest U.S. and stretching east across the
northern Plains will remain well below normal and especially areas of
Montana where sub-zero temperatures are expected through the middle of the
week. Locally the high temperatures will be as much as 10 to 20 degrees
below normal. However, for areas south of the Arctic front involving the
southern tier of the nation from the Southwest east across the southern
Plains, Mid-South and Southeast, record high temperatures are expected
with numerous locations expected to see temperatures reaching into the 80s
which will be locally 20 to 30+ degrees above normal for this time of year.
Orrison
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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