Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 132307
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
307 PM PST Thu Dec 13 2018



.SYNOPSIS...
Dry weather into Friday morning with areas of valley fog. Showers
spreading over the north state Friday with breezy south winds and
light snow over the mountains. A moderate storm system moves
through NorCal late Sunday into Monday with mountain travel
impacts likely.

&&

.DISCUSSION...
Clear and cool tonight with patchy fog in valley locations
under departing high pressure ridge. Storm system over the
eastern Pacific will approach the area Friday and especially
Friday night. System will weaken while moving through NorCal with
mostly dry conditions south of I 80. Rainfall will range from less
than 0.10 Sacramento area to 0.50 or higher Redding area. Snow
amounts will be light with only 1-2 inches above 6000 feet
I80/highway 50 corridor. The system will cause gusty winds over
the mountains with gusts up to 60 mph over the high Sierra
mountains above 7000 feet.

Brief break in the precip Saturday before a stronger system moves
through Sunday and Monday. This system looks to have enough
moisture to cause moderate travel impacts over the Sierra with a
quick shot of heavy snow possible, up to a foot or more late
Sunday night/early Monday morning above 5500 feet. Two
day(Sun/Mon) rainfall amounts from 1-2 inches are also possible.
There is still some uncertainty with this system and confidence in
rain and snow amounts are only medium. We should have a better
handle on the details of this storm system tomorrow.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)
A low pressure system will be passing over northern California
early Monday morning bringing rain and mountain snow to the
region. The bulk of the precipitation is forecast to fall between
midnight and 9AM with showers expected for the afternoon. There is
some uncertainty as to what will happen for the rest of the week
as the ECMWF and the GFS vastly differ. The ECMWF tries to push
another system into northwest California, which would clip our
most northern counties; however, the GFS supports ridging over the
area. If the GFS pans out, we`d like see drier and warmer weather
with the potential for some valley fog. Models then try to come
back into agreement for Thursday/Friday with both having a weak
system advance towards the region. The GFS seems to be faster and
lighter while the ECMWF is slower and brings the precip in on
Friday. &&

.AVIATION...
VFR conditions are expected until early tomorrow some MVFR and
locally IFR visibilities may be possible again in the morning
south of KSAC. Precipitation will begin to move into Northern
Californa after 18Z tomorrow which will reduce both ceilings and
visibilities.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 10 AM to 10 PM PST Friday for West Slope
Northern Sierra Nevada.

&&

$$


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