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000 
FXUS66 KSTO 192335
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
335 PM PST Fri Jan 19 2018

.Synopsis...
Showers and a few thunderstorms will taper off across the region
by this evening. The active weather pattern will continue with
a series of storms, the first Sunday through Monday, followed by
another mid week.

&&

.Discussion...
Scattered showers and isolated thunderstorms are developing this 
afternoon with instability from daytime heating and cold air 
aloft. his convective activity is expected to increase further 
through the rest of the afternoon, then quickly weaken as the sun
sets. So far, a few isolated thunderstorms have formed in the 
Redding Red Bluff area, but have been weak and short lived. Any
additional storms that form are not expected to be strong, with a
brief period of heavy rain and small hail possible.

Snow showers could locally produce some light snow accumulations
over the mountains, but no significant impacts are expected for
the rest of the day/evening. The Winter Storm Warning and 
Advisory have been cancelled. 

As this storm exits, attention turns to another cool system
arriving Sunday, and continuing through Monday. A Winter Storm
Watch has been issued for this system. Heavy snow is possible for
the mountains north of I80, including the mountains of Shasta
County, northern Coastal Range, and mountains of western Plumas 
County and Lassen National Park. Snow levels are expected to drop 
to 2500 to 3000 feet, and storm total snow amounts of 8 to 16 
inches are currently projected. Snow could potentially impact 
travel on area freeways, including I5 and Highway 299. Snow 
amounts over the I80 corridor southward do not look as high, but 
could potentially be enough for a Winter Weather Advisory, with 
around 4 to 8 inches of accumulation. EK

&&
.EXTENDED DISCUSSION (Tuesday THROUGH Friday)
Wet weather continues next week as another weather system pushes 
through the west. Multiple shortwave troughs embedded within the 
larger low pressure system produce a chance of precipitation 
Tuesday through Thursday for interior NorCal. In general, this is 
expected to be another colder storm with snow levels 4000 to 6000 
feet. Precipitation amounts keep flip-flopping this far out, 
though valley locations could see anywhere from 0.3 to 1 inch and 
foothill and mountain locations could get 1 to 3 inches. With 
these liquid precipitation amounts, the mountains are forecast to 
receive up to a foot and a half of snow at the higher elevations. 
Drier weather expected on Friday through the weekend as models 
show slight ridging behind the passage of the low. HEC


&&

.AVIATION...
VFR conditions at all TAF sites. Light isolated showers and 
possibly a thunderstorm are possible across the area through 3z 
Saturday. Localized MVFR conditions within these areas. Light 
winds generally less than 15 kts. HEC &&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Sunday morning through Monday morning 
for Mountains Southwestern Shasta County to Northern Lake County-
Shasta Lake Area / Northern Shasta County-Western Plumas 

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