Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 202358

Area Forecast Discussion
National Weather Service Sacramento CA
358 PM PST Mon Nov 20 2017

Weather system will continue to bring chances of rain tonight,
mainly from I80 northward and in the mountains. Mainly dry
weather is then expected through Wednesday with light rain
chances for the northern mountains. Another weak system will bring
light rain on Thanksgiving into Friday, mainly north of I80.


A weak system with an ample moisture supply from a Pacific plume
but little else is moving through Northern California. Some
locations in the mountains of Shasta and western Plumas counties
have received as much as an inch and a third. The northern
Sacramento Valley has up to a half inch so far. Areas south of
I80 have seen much less, for the southern Sacramento Valley
generally a trace to a few hundredths, virtually northing for the
San Joaquin Valley. Snow levels are high (over 10000 feet) with
this mild system.

Light precipitation will continue into the early evening, but
will drop off in intensity and coverage fairly quickly. Some
overnight mist could develop, though cloud coverage will limit
dense fog development. Have included just a narrow band of some
patchy fog for Tuesday morning for the eastern suburbs of
Sacramento and banking up against the foothills just east of
Stockton and Modesto.

Dry weather returns for most of the area Tuesday and Wednesday as
high pressure ridging strengthens over the West ahead of the
deepening trough over the Gulf of Alaska. A few light showers
remain possible over Shasta County, though. Temperatures will be
unseasonably mild with upper 60s and lower 70s expected through
the Central Valley (around 10 degrees above average). Fog could be
more extensive Wednesday morning, though northerly winds should
limit this in the Valley to around Sacramento southward, where
light southeast winds/calm conditions are expected.

Another weak system will move through the ridge on Thanksgiving
and may bring some light rain to portions of the area, again
mainly north of I80. This system is expected to have less rainfall
than the current system. Snow levels again look high (over 10000
feet), so snow will not be an issue for holiday travel.
Temperatures on Thanksgiving will be quite mild, reaching low 70s
in portion of the Valley. While warm, these are not record levels.
For downtown Sacramento, the record high on Thursday is 80
degrees. EK


A frontal boundary will be setting up over NorCal for the start of
the extended period. This will bring some shower chances with the
best chances north of I-80 and mainly in the higher elevations.
Snow levels will remain high and travel impact should be low for
the weekend but you may have to deal with wet roads at times. The
trough drops south on Monday and this will bring a better chance
for precip across the area. There is some disagreement
on trough placement but there is good agreement on rain chances.
We will also see lower snow levels and they will likely fall
below pass level. Mild temperatures will continue for the start of
the period but will return to near normal by early next week.



Areas of MVFR/IFR will be possible through 03z Tuesday due to
low cig and low vis mainly in scattered showers. Patchy fog and
low cigs possible after 12z Tuesday at the southern terminals,
MVFR/IFR possible. Improving conditions after 17z Tuesday. Winds
remain under 10 knots.


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