Area Forecast Discussion
Issued by NWS Sacramento, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS66 KSTO 040442

TTAA00 KMTR 040335

940 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.


Upper low over Norcal will be dropping SSWwd to just S of the SFO
Bay area by 06z and S of our CWA by 12z Sun. Strong cyclonic flow
around the low has resulted in precip trending a little farther Wwd
over our CWA and we adjusted the PoP line a little farther Wwd to
include Solano Co per the HRRR model. T-storms have been pulsing and
mainly in the NErn quadrant of the upper low. As the upper low
continues to drop SSWwd tonite...the precip/isolated clusters of
T-storms should also sag Swd. Instability may linger past 06z so
have updated the forecasts to include a chance of thunder past the
midnite hour mainly S of Plumas/Sierra Co-KCIC line.

Leading edge of Nly winds has also been evident on radar as line of
convergence and initiating showers/storms along the convergent zone.
The activity has been quick to pulse up/down and may include small
hail. Behind the line the Nly winds are increasing and more or less
verifying the wind advsry at several of the sites. Valley winds on
the wane at press time...and will likely let advsry for the
valley expire at 11 pm.  JHM

.Previous Discussion...

Total rain amounts will mostly be 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

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


$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.