…Strong atmospheric river continues to impact northern California with
heavy rain and life-threatening flooding through Friday…
…Developing storm system forecast to bring another round of gusty winds
to the Pacific Northwest on Friday with heavy mountain snow spreading
toward the northern Rockies this weekend…
…Unsettled weather expected across much of the Northeast and Great Lakes
over the next few days, including the likelihood of heavy snow in the
central Appalachians and higher elevations of northeastern Pennsylvania
and southern New York…
The big weather story is the heavy rain and flood threat in the Pacific
Northwest into early Saturday, though the greatest risk for flooding is
ongoing today, Thursday Nov 21st, with the peak of the atmospheric river
transport into southern Oregon and northern California. Several inches of
rainfall are still possible, around 5-7 inches remain possible over 48
hours with isolated areas in terrain to see 10 + inches of rain. Northern
California is under a High Risk for Excessive Rainfall and a Moderate Risk
goes northward into southern Oregon. For Friday, the atmospheric river
will be waning, but the atmosphere may still drop a couple of more inches
of rain onto saturated soils. Therefore, most of the coastal plain from
northern California to southern Oregon remain under a Slight Risk for
Excessive Rainfall. The Sierra Nevada mountain range will be under a
Moderate Risk for Excessive Rainfall with some rain totals greater than 3+
locally on Friday; additionally, snow levels will be high as warm
advection moves in so areas of higher elevation may see heavy rain as well
on top of snow pack.
The coastal plains and areas of higher elevation in the Pacific Northwest
will continue to face hazardous coastal erosion and strong winds as
another strong area of low pressure develops offshore. High Wind Warnings
are up through Friday morning and the forecast calls for winds in the
45-65 mph range. Power outages are possible and unsecured items may get
blown over. Then, states in the northern Rockies like Montana and Idaho
and the Sierra Nevada in California will have the chance for heavy
snowfall Friday into Saturday as the moisture plume begins to advance
inland over the Northwest.
November snowfall is also in the forecast for parts of the Northeast and
Great Lakes thanks to a potent upper-level low swinging over the region.
At the surface, a compact area of low pressure is currently looping around
the Great Lakes with an eventual southward trajectory over the northern
Ohio Valley. Some light to moderate snow is ongoing this afternoon across
the Ohio and Tennessee River Valleys as far south as Kentucky. The
combination of cold surface temperatues and moisture from the low pressure
will then maximize snowfall totals in the central Appalachians where over
a foot of snowfall is more than possible, and a Winter Storm Warning is
active over terrain in West Virginia for blowing snow and reduced
visibility, winds of 25-45 mph, and possible power outages from wet snow.
A separate area of low pressure developing near Long Island today is also
expected to track in a looping orientation across the Northeast through
Friday, while also producing periods of heavy snow in areas of higher
terrain in the Northeast and Mid-Atlantic.The greatest chances for at
least 6 inches of snowfall is found across northeast Pennsylvania and
southern New York, including the Pocono and Catskill mountains. Locations
in the Washington-Philadelphia metro may also see a snowflake or two, but
accumulations chances are low along the I95 corridor. Coastal areas in the
Northeast and Mid-Atlantic will be rather blustery and raw with rain
showers and temperatures in the 30s and 40s through Saturday, though the
precipitation totals should hover around an inch at the heaviest.
The central and southern U.S. can expect much more tranquil conditions as
high pressure creates a void in the unsettled weather impacting both the
East and West coasts. However, below average temperatures are forecast
from the Mississippi Valley to the Southeast as breezy northwest flow
ushers in a colder airmass. Freeze warnings are active across areas in the
Deep South with lows dropping near to or below freezing.
Wilder
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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