Area Forecast Discussion
Issued by NWS Sacramento, CA

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838
FXUS66 KSTO 232340
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
340 PM PST Tue Jan 23 2018


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

&&

.Discussion...
Strong Pacific storm system will sweep east across NorCal
Wednesday with periods of heavy mountain snow lasting into Friday.
Initial band of Precip will impact Shasta county and the Coastal
Range during the morning and move into the Sierra during the late
afternoon and continue through the evening. Snow levels will start
near 5000 feet but fall to 3000 feet by morning...snow levels may
briefly fall to 1500 feet at times over Shasta county. A burst of
snow with rates greater than 1 inch per hour will be possible
over the Sierra between 4-11 pm. Travel is discouraged during this
time, as visibilities may also be near zero. 1 to 2 feet of snow
will be possible over the Sierra above 4000 feet including areas
along Interstate 80 and Highway 50 with 4 to 6 inches along
Interstate 5 above 2000 feet through Friday morning. The heaviest
snow for Interstate 5 will be late Wednesday night into Friday. A
winter storm warning is in effect for the Sierra above 4000 feet
from noon Wednesday through 10 am Friday and a winter weather
advisory is in effect for the Coastal Range and Shasta county
above 2000 feet 5 pm Wednesday.

A brief bout of valley fog will be possible late tonight into
Wednesday morning, as skies clear just enough overnight.

A second impulse along with increased instability will enhance
mountain snow showers Thursday afternoon. This system may also
cause valley thunderstorms with small as the primary threat. Total
valley rainfall amounts will generally range from 0.50-1.00
inches. Mountain snow showers will linger into Friday, but taper
off by afternoon.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Flat upper level ridging builds across interior NorCal over the
weekend, pushing the storm track to our north. Shortwave energy
moving across the Pacific Northwest will bring a slight chance of
precipitation over the northern mountains, and the northern
Sacramento Valley on Saturday. Otherwise, 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.


&&

.AVIATION...

VFR conditions through this evening with light and variable
winds. Some haze/br may reform across southern Sac and northern
San Joaquin valleys overnight ahead of next storm system. 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 Wednesday to 10 AM PST Friday for
West Slope Northern Sierra Nevada-Western Plumas County/Lassen
Park.

Winter Weather Advisory from 4 PM Wednesday 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.

&&

$$



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