Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 211618

918 AM PDT Thu May 21 2015

Mild weather with mountain showers and thunderstorms will continue
through Friday. Warmer temperatures with fewer mountain showers
expected this weekend into next week.


A broad upper level trough remains quasi-stationary along the West
Coast, with blocking ridge situated over the Rockies. Several
shortwaves have been rotating around this upper trough, and the
next one is moving toward the California coast today. Doppler
radar is detecting a few showers over the mountains. The marine
layer remains at very deep levels along the coast, and a
considerable amount of marine stratus is pushing through the Delta
into the Valley this morning.

Another round of showers and thunderstorms will be developing
today across interior Northern California mountains today.
Steering flow will be a SE to easterly direction today, which is a
more favorable direction for convection on the west slopes of the
Sierra. Elevated instability doesnt look as good as yesterday,
though we still cant rule out a few stray showers reaching the
Valley floor this evening into Friday morning. Hi-Res models show
a considerable amount of precipitation falling along the Sierra
today. It wouldnt be surprising to see some snow accumulations
along the high Sierra passes south of Tahoe.

The aforementioned shortwave pushes south toward Southern
California on Friday, with steering flow becoming more northerly.
While we should still expect some mountain showers and
thunderstorms Friday afternoon, they shouldn`t be as widespread.

Northerly flow aloft will continue over Northern California
through the weekend. This should promote warmer weather, with
temperatures closer to normal. Isolated showers will still be
possible over the mountains, but confined to primarily Lake Tahoe
and southward.



.Extended Discussion (Monday through Thursday)

Starting to sound like a broken record, but models continue to
illustrate a slightly unsettled environment for the extended forecast.
Valley should remain dry while instability persists over
mountains which could trigger showers and afternoon/evening
thunderstorms. Daytime highs in the valley will generally be in
the low to mid 80s with 70s in Delta Breeze influenced areas.
Mountain highs will range in the 50s/60s while Foothills warm into
the 70s. JBB



Onshore flow this morning has allowed low clouds to move through
the Delta region into Sacramento area and are banking up against
the Sierra Foothills. MVFR conditions this morning for that
vicinity through 16-18z, otherwise, the rest of our CWA will be VFR. Delta
breeze will continue to range 15-25 kts with gusts up to 30 kts
today. TAF sites will be fairly light (around 10 kts or less)
except for KSMF, KSAC, KMHR, KSCK between 17-04z when the delta
breeze enhances and increases winds at these sites with speeds
between 10-20 kts.  JBB


.STO Watches/Warnings/Advisories...

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