Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 222225
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
225 PM PST Sun Jan 22 2017

.Synopsis...
Showers and isolated thunderstorms with mountain snow showers
continue tonight into Monday. Drier weather Tuesday into the
weekend except for a slight chance of some light mountain showers
midweek.

&&

.Discussion...
Frontal system is well south of the forecast area this afternoon
with vertically stacked system currently off the Central Oregon
coast. Afternoon deep moist convection has been limited so far
with one lone thunderstorm which developed near KDAX and is
tracking to the NE. Satellite imagery showing some cirrus shield
moving over the area which is helping to limit surface heating.
High resolution models showing showers increasing this evening
over the southern two thirds of the CWA as short wave currently
near base of main low swings inland. Precipitation expected to
increase in the Motherlode and Northern Sierra Nevada tonight with
periods of heavy precipitation. Snow levels will gradually lower
into the upper foothills overnight. A few inches of snow
accumulation possible above 2500 feet in the Coastal and Shasta
mountains and in the NE foothills and Motherlode. Snow amounts
will vary due to showery nature. At the higher mountain elevations
in the Sierra Nevada, an additional 1 to 3 feet is possible overnight
into Monday.

Quasistationary stacked system progged to dig slowly off the West
Coast Monday as it fills. Continued threat of showers and isolated
afternoon thunderstorms Monday. Snow showers continue to be a
possibility in the mountains Monday but any additional
accumulations expected to be light.

Drier northerly flow sets up on Tuesday as upper ridging
approaches the West Coast and subsidence increases over Interior
NorCal.

PCH

&&
.EXTENDED DISCUSSION (Thursday THROUGH Sunday)
Scattered rain and snow showers are possible on Thursday, which
will be mainly confined to the foothills and the Sierra. A
building shortwave ridge of high pressure over the Pacific is
consistently depicted in model forecasts behind a weak positively
tilted upper level trough exiting the region Thursday. The
lingering trough could bring some shower activity, but no
significant precipitation is expected at this time.

Upper ridge builds into northern California on Friday and into the
weekend to bring dry weather and plenty of sunshine. Temperatures
Thursday/Friday will be on the cooler side of normal, but a
gradual warm up in temperatures is expected for the weekend with a
return to normal or slightly warmer than average conditions.

&&

.AVIATION...
For Cntrl Vly, Nrn and Cstl mtns, mnly VFR conds exc lcl MVFR/IFR
in showers. Isold tsra/tsrags poss til arnd 03z Mon. For Wrn
Plumas and Siernev mtns, wdsprd MVFR/IFR conds with lcl LIFR in
shwrs nxt 24 hrs. Sn lvls lwrg to arnd 025 ft amsl tngt.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 4 AM PST Monday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$



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