Flood and Heavy Snow in California, January 4 to 6, 2016

Area Forecast Discussion
National Weather Service Sacramento CA
345 AM PST MON JAN 4 2016

.SYNOPSIS...
Unsettled weather this week with several systems moving through
the area. Rain and mountain snow is likely from time to time,
especially into Tuesday, and later Wednesday into Thursday.

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.DISCUSSION...
Showers only making slow progress inland overnight as a weak
trough ahead of the approaching Pacific low takes its time moving
eastward into the ridge over the West. All the cloud cover is
resulting in rather mild temperatures across the region with
readings presently in the upper 30s to mid 40s in the Central
Valley with 20s and 30s in the mountains.

Initial shower band will continue to edge slowly inland this
morning with rain expected to hold off in the Sacramento area
until after the morning commute. Mostly light rain is expected in
the valley through the midday hours before the band of
precipitation moves into the northern Sierra in the afternoon
where some light snow will be possible.

More significant precipitation and stronger winds will develop
over interior NorCal tonight into Tuesday as the trough presently
west of 130W moves onshore. This system will have a tap to a
deeper TPW plume of around an inch and stronger forcing for
heavier precip. Snow levels briefly bump up to 5000-6000 feet
tonight, but then lower Tuesday as the trough moves in. A half
inch to an inch of rain may fall in the valley with up to 3 inches
in the mountains. A winter storm warning has been posted with a
foot of snow possible across the passes.

Precipitation turns showery behind the front Tuesday afternoon
with lowering snow levels with a period of clearing possible in
the valley behind the front. Forecast soundings across the
Sacramento Valley indicate a good amount of shear and MU CAPE in
excess of 500 J/KG in the afternoon, so we'll be keeping an eye
on the timing of the main frontal band for the possibility of some
stronger thunderstorms.

Precip forecast to taper a bit Tuesday night with short-wave
ridging, then storm number two moves in Wednesday and number three
on Thursday with the main upper low.

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.EXTENDED DISCUSSION (Friday THROUGH Monday)...
An upper ridge over the Eastern Pacific will move into the West
Coast on Friday causing shower activity to taper off throughout
the day. Although, the unsettled pattern may not entirely ward off
all precipitation chances. By Saturday morning, the next wave is
forecast to move into NorCal bringing wet weather, followed by a
drier spell Sunday night. Then another dose of wetter weather
comes Monday into early Tuesday. JClapp

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.AVIATION...
Trough spreading light rain northeastward today and increasing in
intensity overnight. MVFR probable this afternoon with areas of
IFR in mountain. Freezing level remains between 040-050 MSL. S
winds 30-40 kts 050-100 MSL with relatively light surface winds.
JClapp

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.STO Watches/Warnings/Advisories...
Winter Storm Warning from 10 PM this evening to 10 PM PST
Tuesday for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

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