Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 180517
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
917 PM PST Tue Jan 17 2017


.Synopsis...
Dry today, then a series of winter storms will begin Wednesday
and continue into early next week.

&&
.Discussion...
Some light rain is spreading across the coastal range and into the
northern and central valley as of 9 pm. Some patches of fog have
developed this evening ahead of the system over the Southern
Sacramento and Northern San Joaquin Valleys. A few patches of
dense fog may form during the overnight hours ahead of the
system. Precipitation will spread southward during the morning
with the main part of the rain moving through the central valley
during the afternoon and evening hours. Strong winds will increase
first over the north end of the valley by late morning then
spread south during the afternoon. The strongest winds over the
north look to occur during the afternoon hours while further south
it will be in the late afternoon and early evening hours.

The system looks like a decent winter storm with the higher
totals focused over the north. Though Thursday afternoon (0.75)
to (1.25) inches of rain is expected in the central valley with up
to (2.00) inches in the north. (1.00) to (5.00) inches for the
foothills and mountains with the higher totals over Butte County,
Western Shasta County and the Coastal range. (15.0) to (20.0)
inches of snow can be expected near major pass levels with (3.0)
to (6.0) inches between 4000 and 5000 feet. Locally lower levels
may occur over Shasta County.

Snow levels will remain fairly low and near 3500 ft through
Thursday with showers continuing through the day. Locally lower
snow levels may occur if convective showers develop during the
day. Models continue to indicate the Fridays system to be weaker
than this current one. Only exception will be in the mountains
where snowfall amounts looks to be similar through Saturday
afternoon.

.Previous Discussion...
An elongated upper ridge remains draped over California, extending
inland toward the northern Rockies. High clouds in advance of an
approaching weather system have been spreading across the region
today. Low clouds and fog formed across the western half of the
Central Valley this morning, and has been very stubborn in eroding
today. As such, temperatures have managed to climb only into the
mid 40s across the Valley. With a modestly strong temperature
inversion in place, temperatures in the Sierra foothills are in
the mid 50s.

The first in a series of winter storms is currently well off the
Pacific Northwest coast. Warm advection precipitation will start
along the Northern CA Coastal Ranges as early as this evening,
with the main frontal precipitation expected Wednesday into
Wednesday night. This system doesn`t appear to be as wet as last
week`s storms, with rain forecast totals of 0.50 to 1.50 inches
across the Valley, and 1 to 3 inches over the mountains. Snow
levels should primarily hover between 4000 and 5000 feet, with
over a foot of snow accumulation forecast over higher terrain.
South wind gusts of 35 to 45 mph will be possible across the
Valley.

Showery, off-and-on type weather should continue into Thursday,
in advance of the next wintry weather system on Friday. The Friday
system is trending a bit drier. While precipitation is still
expected across the region, we`re now forecasting a bit less in
the way of rain and snow totals than the first storm. Snow levels
are still expected to be lower than the first storm, potentially
down into the Sierra foothills and impacting Interstate 5 through
Shasta County.

Dang

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)


Weak upper ridging moves through Saturday with models suggesting
lingering showers possible over the mountains. The next weather
system then brings precipitation across the area Saturday night
into Sunday. A decent amount of QPF is expected as models showing
a slightly downward trend from 2+ last model runs to only around
1.5 inches in portions of the Central Valley Sunday through
Monday with 2 to 5 inches in the foothills and mountains. Snow
possible down into the foothills with this system and several
feet of new snow expected above 5000 feet impacting travel.
Strong southerly winds forecast Sunday for portions of Interior
NorCal. Decreasing showers Tuesday as weak high pressure returns
to the forecast area.        JClapp
&&

.AVIATION...


Pacific frontal system moves into the area tonight. Mid to high
clouds keeping IFR stratus over much of Central Valley south of
Sutter Buttes this evening. Expect much of Sac and northern San
Joaquin Valley to drop back into LIFR/VLIFR this evening. Sfc to
3000 ft MSL winds increasing Wed after 18z, with sustained 40 to
50 kt at 3000 ft MSL over Valley. Precip to begin tonight up
north and expand southward throughout Wed.     JClapp


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 10 AM Wednesday to noon PST Thursday
for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

Wind Advisory from 4 PM Wednesday to midnight PST Wednesday
night for Carquinez Strait and Delta-Central Sacramento Valley-
Motherlode-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Southern
Sacramento Valley.

&&

$$



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