Area Forecast Discussion
Issued by NWS Sacramento, CA

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829
FXUS66 KSTO 221023
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
323 AM PDT Fri May 22 2015

.Synopsis...
Mild weather with mainly mountain showers and thunderstorms will
continue today. Warmer temperatures with fewer mountain showers
expected this weekend into next week.

&&

.Discussion...
Upper low center just off the coast of point Concepcion this
morning and moving to the southeast. Upper level deformation zone
over the Great Basin contained numerous showers during the day on
Thursday but most of these showers had dissipated by the early
morning hours this morning. As for our CWA this morning...a few
dissipating showers have drifted southwestward into the Northern
Sierra with remnant clouds and partly cloudy skies elsewhere. Main
upper low center is forecast to track through southern California
today. Stability proggs show slightly unstable conditions over the
mountain areas today under broad upper trough and cyclonic flow.
Scattered mountain thunderstorms are a likely occurrence again
today. Steering current today will be out of the northeast so not
out of the question that some of these showers will make it into
the valley at least in the form of dissipating showers or
thunderstorms. Cool airmass and variable cloud cover will keep
temperatures down a little below normal today. Upper trough axis
shifts to the eastern Great Basin on Saturday with Eastern Pacific
ridging starting to push inland over the area for a slight
warming. Still a threat of showers or thunderstorms over the
Sierra however as wrap around moisture pushes over the Sierra
crest. Still a bit more warming on Sunday with daytime highs
most areas pushing above normal for the first time in a few
weeks. With only slight movement of Great Basin trough...wrap
around moisture and Sierra crest showers or Thunderstorms remain a
possibility Sunday afternoon. Mid range models now in better
agreement in placing a weak low center over Washington state by
Monday afternoon with a trough sagging down over Northwest
California. This system showing enough instability and upward
motion for a threat of showers over the northern mountains and
Sierra. Otherwise...mainly fair skies and slightly above normal
temperatures continue.
&&

.Extended Discussion (Tuesday through Friday)

Trough pattern forecast to linger, albeit weaker, through the
extended period continuing a chance of daily diurnal deep
convection over the mountains while temperatures return to near
normal.

&&

.Aviation...

General VFR conditions expected next 24 hours except areas of MVFR
with local IFR conditions over the northern Sierra Nevada vicinity
showers. Isolated thunderstorms over the mountains 20Z-02Z. Chance
for MVFR ceilings in the Delta through about 17Z. Local westerly
wind gusts 20-25 kts after 20Z in the Delta and northern San
Joaquin Valley.

&&

.STO Watches/Warnings/Advisories...
None.
&&

$$







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