Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 201035
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
335 AM PDT Wed Mar 20 2019

.SYNOPSIS...
Periods of light rain and mountain snow mainly today, Friday and
then early next week. Enough snowfall possible for travel delays
over the Sierra during each round of precipitation but light rain
over the lower elevations will only create minimal impacts.

&&

.DISCUSSION...
Negatively tilted upper level trough moving into Norcal with
shortwave rotating northward ahead of this trough bringing light
precipitation across much of the forecast area. Blue Canyon ASOS
showing a switch over to light snow with temperature at one
degree Celsius so snow levels a little above 5000 feet look okay.
Cloud cover and cooler air with the low will bring down daytime
highs today back down to a little below normal for this time of
year. Stability progs indicate enough instability associated with
the low this afternoon for a threat of thunderstorms over most of
the valley and foothills. Upper trough axis shifts inland over
night tonight taking most of the lingering shower threat to the
Sierra while showers end at the lower elevations. Upper trough
axis moves in to the Great Basin on Thursday but cyclonic flow
over the state will keep a threat of showers going over the
mountains. May see a brief break in precipitation over the CWA
Thursday night as small shortwave ridge slides quickly over the
state. Models bring light precipitation into norcal as early as
Friday morning with the frontal band pushing through the north
state Friday afternoon and evening. Precipitation amounts are
again expected to remain on the light side but there could be
enough snowfall over the higher elevations to bring travel impacts
to the Sierra Cascade range. Showers will continua going into the
weekend as the main upper low moves onshore.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)


Little change to the extended forecast package this morning. Weak
high pressure is forecast to build over California on Sunday
allowing for warm and dry conditions over Northern California.
This will likely be short lived though as a broad low pressure
system advances towards the west coast. Model and ensemble
guidance continue to hint at cooler and wetter weather for the
week, with rain returning to CWA as early as Monday morning. The
low remains quasi-stationary off the coast, which could lead to
wet weather through midweek.


&&

.AVIATION...


Rain will continue to spread over northern California this
morning, which will bring periods of MVFR conditions and an
increase in southerly winds. Thunderstorms are in the forecast
once again from 18Z Wednesday through 03Z Thursday.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM PDT this evening for West
Slope Northern Sierra Nevada.

&&

$$


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