…Unsettled weather to persist across the Northwest U.S. into early next
week with much colder temperatures and heavy snowfall across the Cascades
and the Northern Rockies…
…Strong atmospheric river to bring heavy rains and flooding concerns to
northern California…
…Storm system crossing the Great Lakes region to bring accumulating
snowfall to the Northeast…
…Record high temperatures are expected across portions of the Southwest
out through the Southern Plains on Monday…
A trough of low pressure will be impacting the Pacific Northwest and the
northern Rockies for the remainder of the weekend and into early next
week. Moist onshore flow into the higher terrain coupled with colder
temperatures settling south from southwest Canada will set the stage for
very heavy accumulating snowfall across the Cascades and especially
interior mountain ranges such as the Sawtooth and the Tetons of the
northern Rockies. Generally 1 to 2 feet of new snowfall is expected for
the Cascades, but as much as 2 to 4 feet is expected over the northern
Rockies where the moist upslope flow and colder temperatures will maximize
the snowfall potential.
Some of this very heavy snow over the Northwest will also be influenced by
a strong atmospheric river impacting northern California which is forecast
to bring very heavy rainfall totals into the coastal ranges and the
interior foothills and upslope areas of the northern Sierra Nevada. Going
through Monday, an additional 4 to 8 inches of rain can be expected
locally, with isolated heavier totals. Flooding will become a notable
concern across these areas, and the Weather Prediction Center has issued a
Slight Risk (level 2 of 4) of excessive rainfall. This will include a
threat for some burn scar flash flooding locally with debris flow and
mudslide activity also possible.
Farther off to the east, a storm system currently crossing the Midwest
will advance through the Great Lakes region tonight and will allow for
accumulating snowfall to overspread portions of northern Pennsylvania and
New York along with adjacent areas of New England. Locally as much as 2 to
4+ inches of snow is expected with this system and there will also likely
be some freezing rain/icing concerns for areas of central and western
Pennsylvania. This system will pull away through southeast Canada on
Monday, and gradually a cold front will cross the Great Lakes and
Northeast in its wake with much colder temperatures arriving behind it.
Arctic high pressure will be settling south from Canada across much of the
northern tier of the nation by Monday which will allow for temperatures to
trend locally well below normal. This will especially be the case over the
northern High Plains where temperatures will be as much as 15 to 25
degrees below normal, with daytime highs locally staying below zero.
However, south of the Arctic front, very warm temperatures will be pooled
across much of the southern tier of the country. This will include
temperatures reaching well into the 80s across the interior of the
Southwest and also across the southern Plains. Record high temperatures
are expected for some locations as a result, and for some areas the high
temperatures will be as much as 20 to 30 degrees above normal.
Orrison
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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