Winter Storm Warning 12, NWS Sacramento, CA

Area Forecast Discussion
National Weather Service Sacramento CA
315 AM PDT Thu Mar 23 2017

.Synopsis...
Dry day today then rain and mountain snow returning tonight and
Friday. Sierra snow impacts likely late tonight into Saturday.
Brief break in precip mid weekend but more precipitation early
next week.

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.Discussion...
Radar is clear this morning as upper trough shifts farther into
the Great Basin and high pressure builds over the state. Enough
clearing has occurred to allow some patchy fog to form in the
valley this morning. Once this fog clears, skies should be
generally fair most areas today with daytime highs warming to just
a bit below normal. Upper ridge axis quickly shifts eastward into
the Great Basin tonight with the next upstream frontal system
pushing into norcal by this evening. A moderate precipitable water
plume associated with this system will bring moderate amounts of
precipitation on the order of a half to an inch of rain in the
valley and up to a couple inches over the higher terrain between
late tonight and Saturday. Moderately high snow levels will mean
impacts for Sierra Travel and have issued a winter weather watch
for Sierra zones. At this time, snow amounts appear will come in
at high advisory or low warning amounts so will have to see how
subsequent QPF forecasts pan out. Most precip from this system
will end Saturday morning as the front shifts east of the state
but a few showers will continue Saturday as Norcal remains under
cyclonic flow behind the upper trough axis. Early Sunday looks dry
under upper level ridging so likely to see some patchy valley fog
again Sunday morning. Another quick moving system brings
overrunning precipitation into the north state by Sunday
afternoon. A fairly weak frontal system is forecast to bring light
precipitation to the forecast area Sunday night.

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.EXTENDED DISCUSSION (Monday THROUGH Thursday)

Lingering showers over Interior NorCal Monday as upper trough
moves through then drier weather expected Tuesday and Wednesday
under upper level ridging. Models suggest another short wave
trough will bring a threat of some precipitation mainly over
northern and eastern portions of the forecast area Thursday.

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.AVIATION...

Upr rdg in EPAC blds inld with NWly flow alf. Genly VFR conds
ovr Intr NorCal exc isold MVFR/IFR conds in vly mist/fog til arnd
17z and lcl MVFR/IFR conds poss with pcpn fm nxt stm W of I-5 aft
06z Fri. Lcl Sly sfc wnd gsts to 25 kts poss aft 06z Fri.

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.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from this evening through late Friday night
for Western Plumas County/Lassen Park.

Winter Storm Watch from late tonight through late Friday night
for West Slope Northern Sierra Nevada.

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