Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 032222

322 PM PDT SAT OCT 3 2015

Storm moving into NorCal will bring cooler weather, windy
conditions, and a chance of showers and thunderstorms this
weekend. Showers will linger into Monday over the Sierra Nevada
south of Highway 50.


The approaching storm will be centered over NorCal this evening.
Water Vapor and Visible satellite imagery are showing the
circulation`s center near the OR/CA border this afternoon. On
radar, we are already seeing instability from the storm as
thunderstorms develop east of the Sierra Crest in Lassen County
and also in Western Nevada. The HRRR model indicates that showers
and possible thunderstorms should develop west of the Sierra Crest
after 5 pm this evening...with a slight chance of some showers
working their way into portions of the valley overnight. Showers
expected to continue into Sunday afternoon but will push southward
as the low tracks towards SoCal. Total rain amounts will be very
light in the valley (trace amounts to a few hundredths) while rain
over the western Sierra slopes could range from a tenth of an inch
up to a half inch (locally higher near the crest and in vicinity
of thunderstorms). Snow levels will be above 9000 ft so light snow
amounts are possible near the Sierra Crest.

The primary concern with this storm are the increasing winds as
this storm tracks across our region. 3 pm wind observations at
Redding Airport had gusts close to 40 mph...Sacramento
International gusts near 25 mph...Vacaville gusts near 30 mph.
Strongest north to northeast winds this evening will be in the
Northern/Western Sacramento Valley and the Coastal Range between
Shasta County to Lake County with gusts up to 40 mph for valley
and up to 50 mph in higher terrain. Overnight, northeasterly winds
will also pick up along the western Sierra slopes north of
Interstate 80 with gusts 40-50 mph. Winds could easily knock down
large branches and trees that have been weakened by the drought
and wildfires. Downed trees may cause power outages or damage
vehicles/buildings. Wind advisory remains in effect overnight into
Sunday morning. Winds will gradually lessen throughout the day
Sunday and any shower activity should be limited to areas south of
Interstate 80.

Another concern overnight is whether thunderstorms develop near
burnscars along the Sierra Nevada. Heavy downpours from the
thunderstorms could cause debris flows (ie near the Butte Fire).

Showers may linger over the Sierra south of Highway 50 on Monday
due to wraparound moisture from the Low over southern NV/southeast
CA area. Ridging builds in with gradually increasing temperatures
and dry conditions as the Low weakens and moves eastward.


Upper level high pressure ridging expected to remain over the
western U.S through the extended period. Genreally light winds are
expected through this time. Daytime highs Wednesday are forecast
to come in near to a little above normal. Temperatures will warm
slightly each day reaching several degrees above normal by next



Upper low dropping southward through northern California over
next 24 hours. Scattered Showers and isolated thunderstorms
mainly over the sierra tonight. VFR conditons expected next 24
horus with ceilings above 50k feet. Gusty winds over the
Sacrametno valley...coastal mountains and southern Cascades into
Sunday. North to northeast wind gusts over 40 mph possible.

WIND ADVISORY until 11 AM PDT Sunday for Central Sacramento
Valley-Clear Lake/Southern Lake County-Mountains Southwestern
Shasta County to Northern Lake County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta
Lake Area / Northern Shasta County-Western Plumas County/Lassen

RED FLAG WARNING until 11 AM PDT Sunday for Central Sacramento
Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County
Below 1000 Ft-Eastern Mendocino NF-Eastern Portion of
Shasta/Trinity NF-Lake County Portion of Lake-Napa-Sonoma Unit-
Northern Sacramento Valley to Southern Tehama County Line Below
1000 Ft-Southeast Edge Shasta-Trinity NF and Western Portions of
Tehama-Glenn Unit-Southern Sacramento Valley in Yolo-Sacramento
Far Western Placer, southern Sutter and Solano County Below 1000


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