Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 230356
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
856 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...
Low pressure disturbance off the central coast continues to draw
moisture towards the west into the forecast area this evening.
Areas have settled down south of Plumas county this evening and
showers and thunderstorms have ended. Some showers continue to
moves northwest into the area. Models have some of the showers
spreading into mainly eastern Shasta county later tonight.
For the most part showers with isolated thunderstorms are
expected. The only major concern may be over Burney Basin which
has a chance for some scattered thunderstorms over the next
several hours as a weak disturbance moves northward over the area
and may help to provide enough instability. As this disturbance
moves northward overnight by morning any remaining activity will
be north of the forecast area.

.PREVIOUS 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 09z Wednesday.
Winds generally 5-10 knots but locally higher in any t-storms
and also in the Delta where gusts to 25 knots are possible.

&&

.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
Portions of Tehama-Glenn Unit.

&&

$$



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