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000 
FXUS66 KSTO 221705
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
905 AM PST Mon Jan 22 2018


.Synopsis...
Pacific storm exits the area today. Dry weather Tuesday with some
morning valley fog possible. A stronger system impacts the area 
Wednesday into Friday bringing moderate to heavy rain, mountain 
snow and gusty wind.

&&

.Discussion...
Pacific frontal system pushing through southern portions of the
forecast area this morning. 88D showing some scattered light
showers in Central Valley area with snow showers over the Sierra 
Nevada, where chain controls are in effect. Models indicating 
shower activity will diminish by the afternoon as the system exits
and subsidence increases from the west.

Upper ridging brings drier weather tonight into Tuesday. Some 
morning fog may develop in portions of the Sacramento Valley and 
Northern San Joaquin Valley tomorrow morning. Temperatures trend 
up to near or slightly above normal Tuesday.

Stronger Pacific frontal system is forecast to move through 
Interior NorCal beginning Wednesday. Models similar with timing, 
pushing frontal precip into Western Shasta and the Coastal Range 
by 18z Wed then across Interior NorCal Wednesday into Wednesday 
night. Breezy to windy conditions develop ahead of the front. Snow
levels initially look to be around 4000 to 6000 feet Wednesday 
but lower to 2000 to 4000 feet behind the front Wednesday night 
and Thursday. Upper trough moves through Thursday into early 
Friday keeping unsettled weather over the area. Model storm liquid
QPF ranges from around half and inch to 1.5 inches in the Central
Valley (highest in the Northern Sacramento Valley), and 1 to 3 
inches for the mountains. 1 to 2 feet of snow expected in the 
mountains and will likely be issuing a watch with the afternoon 
package. 

PCH

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)
Area of high pressure will bring mostly dry conditions Friday for
northern California, although a few lingering showers across the 
Cascades and extreme northern Sacramento Valley are possible. The 
next low pressure system to make landfall will affect the Pacific 
northwest and the Cascade/Coastal mountains of the interior, which
will bring another round of precipitation chances for Saturday. 
High pressure returns for Sunday before the next weather making 
system approaches for early next week, mainly affecting the 
northern valley and mountains. 

&&

.AVIATION...
Widespread MVFR to IFR conditions this morning with improving
conditions this afternoon into evening. Mainly VFR Tuesday except
areas MVFR to LIFR conditions in the Central Valley in BR and Fog
between 10z-19z.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM PST this morning for West 
Slope Northern Sierra Nevada-Western Plumas County/Lassen Park.

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