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000 
FXUS66 KSTO 222054
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
154 PM PDT Tue Aug 22 2017

.SYNOPSIS...
Mountain showers and thunderstorms through Wednesday, then dry 
weather returns for the end of the week. Temperatures around 
average through mid-week, then warming for the end of the week.

&&

.DISCUSSION...
Upper level low continues to spin off the central California coast
this afternoon and will linger through Wednesday. Plenty of
moisture and modest instability has led to another afternoon of
showers and thunderstorms over the mountains. Another round will
be possible on Wednesday, though expecting less coverage and have
confined chances to near the Sierra crest. Temperatures will be
near average through Wednesday as onshore flow continues. 

Low moves onshore Thursday, opening up into a trough. Moisture and
instability will decrease, ending chances for thunderstorms.
Temperatures will begin to warm with highs topping out a few
degrees above normal. Ridging builds in for the end of the week
into the weekend with a more substantial warming trend. Quiet 
weather otherwise. 

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
A strong upper level ridge will be set up over the western half 
of the US for the extended period. This will bring quiet weather 
with warm temperatures for the weekend, highs 97-105 expected in 
the Valley and 70's and 80's in the higher elevations. The ridge 
will start to push to the east early next week and we will start 
to see an increase in moisture but mountain thunderstorm chances 
look to remain minimal. Temperatures stay warm into early next 
week but will start a slow cooling trend. 

-CJM 

&&

.AVIATION...
VFR conditions expected at the TAF sites the next 24 hours. 
Scattered Mountain thunderstorms possible through 05z Wednesday. 
Clouds between 15000 and 20000 feet build into the northern part 
of the Valley this evening and VCSH are possible at KRDD and KRBL 
between 01z and 05z Wednesday. Winds generally 5-10 knots but 
locally higher in any shower or t-storms and also in the Delta 
where gusts to 25 knots are possible. 

-CJM

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until midnight PDT tonight for Burney Basin and 
Northeast Plateau in Shasta County Including Northwest Lassen NF 
north of Lassen NP-Eastern Mendocino NF-Eastern Portion of 
Shasta/Trinity NF-Northern Sacramento Valley to Southern Tehama 
County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to 
3000 Ft. Includes portions of Shasta-Trinity and Butte Units-
Northern Sierra Including Lassen NP and Plumas and Lassen NF/S 
West of the Sierra Crest (West of Evans Peak-Grizzly Peak-
Beckworth Peak)-Southeast Edge Shasta-Trinity NF and Western 

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