Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 241207
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
407 AM PST Wed Jan 24 2018

.Synopsis...
Strong Pacific storm impacts the area later today thru Friday
with periods of moderate to heavy rain, mountain snow and gusty
wind. Drier weather over the weekend.

&&

.Discussion...
Offshore frontal system slowly approaching NW California as
upstream trough continues to deepen over the eastern Pacific.
Radar shows precipitation has begun over the northwestern most
counties of the state with heavier precipitation indicated
offshore to the west of Eureka. Inland across interior NorCal,
clouds have begun to thicken to the north of Sacramento, while
relatively clear skies to the south has allowed patches of dense
fog to develop across portions of the Delta and in the northern
San Joaquin Valley.

The front will accelerate southeastward across the region later
today and tonight as the upper trough lifts into the PacNW. Snow
will begin across the northern mountains this afternoon, and over
the northern Sierra by this evening. Heavy snow and gusty winds
will be likely in the mountains overnight as the front traverses
the area, and snowfall rates may exceed 2 inches an hours at times
overnight making for very difficult travel conditions. Snow levels
will lower to 2000-4000 feet by Thursday morning, then lower to
around 1500-3000 feet during the day.

A brief break in the precipitation will be possible early Thursday
before a second impulse along with increased instability moves
onshore. This will enhance mountain snow showers by Thursday
afternoon and may also lead to a few thunderstorms across the
Central Valley.

Total snow accumulations will likely reach 1 to 2 feet across most
of the interior NorCal mountain passes by early Friday. The low
snow levels along with hefty snow accumulations will mean
significant travel delays are likely with lengthy travel distances
with chain requirements. If at all possible, travel over the
passes this morning or delay until Friday or the weekend.

The return of ridging will lead to gradually drier weather Friday
and heading into the weekend.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
Flat upper level ridging builds across interior NorCal Sunday,
pushing the storm track to our north. Dry conditions will prevail
across the forecast area Sunday into Monday. Forecast models
indicate an upper level system moving inland for the beginning of
the next work week. Best dynamics should remain to our north with
only slight chances of precipitation over the northern mountains.
Daytime highs will trend upward by early next week, but will
remain near or slightly above seasonal normals through the
extended forecast.

&&

.AVIATION...
MVFR ceilings for the northern Sacramento valley as rain
approaches with IFR/LIFR conditions for terminals near Sacramento
and southward. Rain and mountain snow moves through the area after
14Z Wednesday and continues into Thursday with breezy northerly
winds and lowered cigs/visibilities in periods of heavier showers.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from noon today to 10 AM PST Friday for
West Slope Northern Sierra Nevada-Western Plumas County/Lassen
Park.

Winter Weather Advisory from 4 PM this afternoon to 10 AM PST
Friday for Burney Basin / Eastern Shasta County-Mountains
Southwestern Shasta County to Northern Lake County-Shasta Lake
Area / Northern Shasta County.

Winter Weather Advisory from 4 PM this afternoon to 6 PM PST
Thursday for Clear Lake/Southern Lake County-Northeast
Foothills/Sacramento Valley.

&&

$$



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