NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
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000
FXUS66 KSTO 210146 CCA
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
233 PM PDT Sun May 20 2018

.SYNOPSIS...
Afternoon and evening thunderstorms possible over higher terrain
much of this week. Seasonal temperatures continue across the
region.
&&

.DISCUSSION...
Getting some showers and isolated thunderstorms over the northern
mountains and along the northern coastal range this afternoon. The
activity is expected to continue into the evening before
tapering.

A low pressure area will move southward overnight through the
central part of California. This may trigger some showers over the
western slopes later at night as it moves towards Southern
California. Unstable air is still forecast for the region with
most of the activity continuing to remain over the mountains and
foothills. Counter-clockwise flow around the low may bring a few
showers or isolated thunderstorms into the valley in the evening
hours on Monday and mainly over the eastern end of the valley from
around Chico southward.

On Tuesday the low will move northeast into the Great Basin with
easterly flow continuing to bring moisture westward back over
Northern California. Continued showers and thunderstorms for the
mountains and foothills is expected. This might also be the best
chance for activity to move over the valley...mainly north of
I-80.

The low over the Great Basin begins to lift northeast on
Wednesday and winds aloft will shift southerly over the region.
Less activity is expected compared to the prior two days. Most of
the activity should stay over the mountains but the north end of
the valley may continue to be under the threat of thunderstorms.

Decent flow will continue through the Delta the next few days and
temperatures for most locations with remain near seasonal normals
with the exception of the north end of the valley which will warm
to around 90 degrees the next couple of days.

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)

Closed upper low off the California coast Thu into Fri, tracks NE
through Interior NorCal Sat. This will continue a threat of
showers and afternoon/evening thunderstorms over the foothills and
mountains, and possibly in the Northern Sacramento Valley. By
Sunday, low is progged into Oregon with a decreased threat of deep
moist convection over the CWA. High temperatures forecast to be
near to slightly above normal through the extended period with 80s
in the Central Valley, and mostly 60s to 70s for the mountains
and foothills.

&&

.AVIATION...

Upr trof ovhd dvlps into upr low ovr Cntrl CA tngt into Mon. VFR
conds ovr Intr NorCal nxt 24 hrs exc wdly sct MVFR/IFR conds poss
in shwrs and aftn tstms omtns. Lcl MVFR/IFR conds poss in ST vcnty
Delta into Srn Sac Vly btwn 10z-18z Mon. Lcl SW-W sfc wnd gsts up
to 25 kts in Delta til arnd 08z tngt, and to 20 kts in Srn
Sac/Nrn San Joaquin vlys til abt 04z.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
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