Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 292209
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
209 PM PST Sun Jan 29 2023

.SYNOPSIS...
Moderate snow with travel impacts and a few light Valley showers
through this evening. There is the potential for near to slightly
below freezing overnight low temperatures through mid-week.
Precipitation returns late in the week.

&&

.Discussion...
An upper low moving southward through the area is bringing
light Valley showers and moderate mountain snow this afternoon.
Observed precipitation amounts have generally ranged from less
than a tenth of an inch to around 0.25-50" across portions of the
central Sacramento Valley and over the Sierra along and north of
I-80. Additional snow accumulations of 3 to 5 inches, locally
higher, can be expected across the northern Sierra; heaviest
amounts through this afternoon. Current snow levels are around
2,500-3000 feet per latest webcams and snow level radar data.
Light accumulations are possible down to 3,000 feet, with less
than an inch down to 2,000 feet. High- resolution guidance shows
additional light Valley showers spreading southward into the
southern Sacramento and northern San Joaquin valleys later this
afternoon into the early evening hours, with Sierra snow lingering
into the evening. Mountain travel will likely be impacted with
slippery roads and chain controls. A Winter Weather Advisory
remains in effect through 7 pm this evening for the northern
Sierra. Dry weather returns tonight through midweek.

North to east winds will continue to increase in this system`s
wake this afternoon and into Monday with a strong surface pressure
gradient developing. Wind gusts of 25-35 mph, locally up to 40
mph, are being observed across portions of the Sacramento Valley
this afternoon. Wind gusts in the 40 to 50 mph range are still
possible along the west side of the Sacramento Valley. Even higher
gusts will be possible for portions of the foothills, with gusts
to 60 mph possible over exposed ridgetops, peaks, and gaps. NBM
continue to show probabilities of 65-100% for wind gusts greater
than 40 mph along the west side of the Sacramento Valley and the
Sierra. A Wind Advisory remains in effect until 1 pm Monday for
the Sacramento Valley, Delta, northeast foothills, northern
Coastal Range, and the Sierra Cascade Range.

A cold airmass filters in behind the system, with overnight
temperatures at or below freezing early to mid-week. The ECMWF
EFI also highlights the potential for cold overnight temperatures.
Valley lows will generally range from the upper 20s to mid 30s. Even
colder overnight lows will be possible Tuesday morning, with
Valley lows around freezing down into the upper 20s, though the
potential for a hard freeze has diminished some. This is largely
due to northerly winds lingering into early Tuesday. NBM
probabilistic guidance of hitting 28 deg F ranges from 15-35
percent. The best potential for hard freeze conditions remains
across the northern San Joaquin Valley, where winds will be
lighter. The mountains will be very cold, with single digits and
potentially some high mountain basins dropping to around zero.
Wednesday morning lows are projected to be a little less cold in
the Valley, generally around 32, with teens in the mountains.

IDS/EK

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...
By late week, low temperatures will trend closer to normal and
much of the area will see relief from the very cold overnight
temperatures. Ensemble guidance suggests another shortwave trough
will move through the area later this week, bringing the potential
for another round of light precipitation chances to interior
northern California late Thursday into Friday. There is still some
uncertainty in the cluster analysis, but overall this system does
not look too impactful. Another system will be possible next
weekend, however there is still quite a bit of uncertainty with
timing and strength.

&&

.AVIATION...
Weather system will continue to move southward today bringing
scattered showers and mountain snow through this evening. VFR
conditions with areas of MVFR in the Valley, and MVFR/IFR
conditions in the mountains through 02Z Monday, then widespread
VFR conditions return. Strong north to east surface wind gusts
25-40 kts, locally higher in the Sierra Nevada through 21Z Monday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 1 PM PST Monday for Carquinez Strait and
Delta-Central Sacramento Valley-Mountains Southwestern Shasta
County to Western Colusa County-Northeast Foothills/Sacramento
Valley-Northern Sacramento Valley-Southern Sacramento Valley-
West Slope Northern Sierra Nevada-Western Plumas County/Lassen
Park.

Winter Weather Advisory until 7 PM PST this evening for West
Slope Northern Sierra Nevada.

&&

$$


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