Area Forecast Discussion
Issued by NWS Sacramento, CA

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384
FXUS66 KSTO 181133
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
333 AM PST Wed Jan 18 2017


.Synopsis...
First in series of winter storms moves through today with another
Friday and a third around Sunday. Higher elevation travel impacts
are likely due to snow and winds today and Thursday with lower
snow levels for the Friday and Sunday storms. Moderate to heavy
rain at the lower elevations with windy conditions today through
this evening and again on Sunday.

&&
.Discussion...
The first in a series of Pacific storm systems is now moving on to
the north coast with a band of warm sector precipitation now
moving through the central valley. So far, precipitation has been
very light and expect it to remain that way until main frontal
band moves through later this afternoon and evening. Cloud cover
associated with the light warm frontal precipitation has not kept
light fog from forming throughout the central valley this morning
but should be enough to keep it from becoming significantly dense.
Precipitation and winds will increase this afternoon as the
Pacific front pushes inland with strong enough winds likely to
warrant wind advisory now in place. Snow picks up this afternoon
as well over the Sierra Cascade range. Snow levels over the Sierra
will drop from around 5500 feet today to 4500 feet this evening
and tonight allowing for significant impacts to trans-Sierra
travel, especially when combined with the strong winds. Over the
northern mountains. with snow levels remaining generally above
3500 feet, impacts there will be minimal although areas above 3000
feet may receive an inch or two of snow this evening when snow
levels are lowest. The frontal band is forecast by models to move
into the Sierra late tonight continuing the precipitation there
while winds and precipitation decrease elsewhere. Showers continue
on Thursday under flat ridging before next Pacific storm system
moves onto the coast Friday morning.

This next system will slide across Norcal on Friday bringing
another round of rain, mountain snow and winds. A look at current
QPF forecasts indicates that this will not be as wet of a storm as
todays system with rainfall amounts about half to three quarter as
much as todays system. Winds will be a little less as well. One
significant difference with this system will be snow levels which
are expected to drop below 3000 feet over Shasta county and below
3500 to 4000 feet over the Sierra Cascade range making mountain
impacts more widespread. Saturday looks like a showery day under
brief flat ridging before next system arrives at the coast
Saturday night.

Cloudy cool conditions throughout the short term
forecast will keep daytime temperatures a little below normal with
overnight lows a bit above.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)

Precipitation spreads across the entire forecast area Saturday
night into Sunday as next Pacific frontal system impacts interior
NorCal. Models have trended down some on QPF and now suggesting
upwards of 1 to 2.5 inches in the Central Valley and foothills
and upwards of 3 to 4 inches in wetter mountain locations. Snow
possible down into the foothills with this system and several feet
of new snow expected at pass levels impacting travel. Strong
southerly winds forecast Sunday and wind advisories may be issued
for portions of Interior NorCal. Decreasing showers Monday into Tuesday
as high pressure returns to the forecast area.
&&

.AVIATION...

Pac fntl sys movg thru Intr NorCal attm with wdsprd MVFR/IFR and
isold LIFR nxt 24 hrs. Areas Sly sfc wnd gsts to 30 kts in Cntrl
Vly tda and S-SW gsts up to 45 kts ovr hyr mtn trrn. Sn lvls
035-045 ovr Nrn/Cstl mtns and 045-055 ovr Wrn Plumas/Siernev mtns
tda into Thu mrng.

&&

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

Wind Advisory from 4 PM this afternoon to midnight PST tonight
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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