Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 211036

Area Forecast Discussion
National Weather Service Sacramento CA
236 AM PST Tue Nov 21 2017

Mainly dry weather this week with rain chances limited to far
northern CA. Wetter system possible early next week.


High pressure has begun to build into California from the south,
bringing clearer skies and forcing the upstream atmospheric river
northward. A few light showers are still present mainly along the
northern CA coast. Nighttime satellite imagery suggests extensive
coverage of low stratus with some fog across the region. Northerly
surface winds are keeping fog from becoming dense thus far

Warm temperatures with mainly dry weather are expected the next
couple of days under strengthening high pressure. Look for high
temperatures to reach the upper 60s to lower 70s across the
Valley, with 50s and 60s over the mountains. These forecast high
temperatures are 5 to 10 degrees warmer than normal for this time
of year, and may be within a couple of degrees of record high

With clearing skies and light winds, Valley fog may develop over
the next few mornings. The most likely areas will be from around
Sacramento southward, and favored mountain basins.

A weak weather system may make its way into NorCal on
Thanksgiving, and may bring a few showers to the region. This
isn`t expected to significantly impact holiday travel however.



Shortwave will move through the area on Saturday into early
Sunday. Majority of moisture plume will be pointed toward the
Pacific NW so local area will just catch the tail end of
precipitation. Shower chances will be mainly for I-80 northward
with heaviest amounts in the mountains. Still not a big soaker by
any means and snow levels will remain high.

Parent low and associated trough will then approach the area
Sunday night and move through on Monday. Models are in better
agreement than past several runs so confidence in forecast is
increasing, though still some uncertainty with precipitation
amounts. Regardless, this system should bring better chances for
more widespread precipitation, again heaviest amounts in the
mountains. The difference with this wave is that snow levels look
to drop below pass levels on Monday as colder air moves in. This
will bring accumulations down to 5000-6000 feet and possible
travel delays over mountain passes. Mild temperatures expected for
the weekend, cooling off a bit by Monday.




Areas of MVFR/IFR will be possible this morning and again on
Wednesday morning due to patchy fog and low cigs. Improving to VFR
conditions during the day. Winds remain under 10 knots.


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