NOAA Forecast Discussion

000
FXUS66 KSTO 151104
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
304 AM PST Fri Dec 15 2017

.Synopsis...
Weak system brings a slight chance of light showers over the
mountains Friday night into early Saturday, otherwise dry through
early next week. Breezy to windy conditions forecast this weekend,
resulting in increased fire concerns.

&&

.Discussion (Today through Monday)...

Upper level high pressure over the region overnight began to show
signs of degradation as a shortwave trough approached in the
eastern Pacific. Water vapor imagery showed increasing amounts of
moisture streaming ahead of the approaching disturbance with
increasing high level clouds for northern California.

Short range models continue to be in good agreement to tracking a
shortwave trough of low pressure aloft through northern California
tonight and exiting by early Saturday. This system will bring
increasing cloud cover and some chances for light rain for the
northern mountains and high Sierra elevations.

The most impactful weather will be as the system passes and
northerly winds develop Saturday. Pressure gradients across the
valley and mountains will allow gusty winds to develop. The
combination of dry fuels with a lack of recent rainfall, low
relative humidities and windy conditions will provide critical
fire weather conditions for portions of the valley and west valley
foothills/mountains. Outdoor burning is discouraged.

Calmer winds will return Sunday into Monday as another upper level
high pressure system develops and returns to northern California
to provide dry conditions and above normal temperatures.

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Models continue in agreement with a cold Pacific storm system
dropping south mid-week. This system breaks down the ridge rather
rapidly and brings a few impulses of precipitation across Northern
California. Current forecast reflects precip chances Wed-Thur with
possible pattern change. This system appears to be rather dry
with only light rain and snow amounts expected. Relatively low
confidence remains with specific system details.

&&

.AVIATION...

VFR/MVFR conditions across interior NorCal the next 24 hours
except local MVFR/IFR conditions in BR for the southern Sacramento
and northern San Joaquin Valleys. Valley winds generally below 10
knots.

Shoe/Dang

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 PM this evening to 10 AM PST Sunday for
Carquinez Strait and Delta-Central Sacramento Valley in Glenn,
Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-
Eastern Mendocino NF-Lake County Portion of Lake-Napa-Sonoma
Unit-Northern San Joaquin Valley in San Joaquin and Stanislaus
Counties 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 Ft.

Wind Advisory from 4 AM to 4 PM PST Saturday for Carquinez
Strait and Delta-Central Sacramento Valley-Clear Lake/Southern
Lake County-Mountains Southwestern Shasta County to Northern
Lake County-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Southern
Sacramento Valley.

&&

$$

NWS STO Office Area Forecast Discussion

Information from NOAA - National Oceanic and Atmospheric Administration

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