NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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000
FXUS66 KSTO 212105
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
205 PM PDT Thu Mar 21 2024

.Synopsis...
Dry and warm weather will continue until Friday. Widespread rain,
high elevation snow, breezy winds, and cooler weather return as
we move into the weekend with the arrival of our next impactful
weather system.

&&

.Discussion...
The strong ridge from earlier this week has broken down and
shifted east allowing occasional bands of high clouds to move
across the region. Currently skies are mostly clear with
temperatures mainly in the 30s and 40s over the mountains, and
upper 40s and 50s across the Central Valley. Onshore surface
pressure gradient has picked up a little compared to 24 hours ago
and southerly winds of 5-10 mph prevail through the Sacramento
Valley with a few gusts of 20-25 mph over the mountains.

Enough ridging remains overhead for another day of dry weather and
mild temperatures. Highs today will be mostly in the lower to mid
70s across the Central Valley with 50s and 60s over the mountains.

The upstream closed low off the coast of the PacNW is forecast to
drift closer to NorCal on Friday before moving in over the
weekend. Precipitation is forecast to begin over the Coast Range
and Shasta County by late Friday morning, then spread southeast
with a cold front reaching the I-80 corridor from the Sacramento
area up into the northern Sierra by Friday evening. Showery and
cooler weather is expected Saturday, then shower chances mostly
retreat to the mountains on Sunday.

Minor to moderate impacts are expected as the system moves through
bringing rain, mountain snow, gusty wind and thunderstorm chances.
QPF of 0.50" to 1" is forecast through the valley with 1.50" to 3"
over the foothills and mountains.

Snowfall accumulations of 8-18 inches are expected above 6k ft
with lighter accumulations down to around 4k ft. Amounts up to 3
ft will be possible over the higher peaks. Heaviest snow is
expected Friday night and Saturday resulting in travel delays over
the higher northern Sierra passes.

A few thunderstorms will be possible with the front as it moves
through Friday afternoon and evening, but a better chance of
thunderstorms is expected Saturday afternoon as the upper trough
moves overhead. Brief heavy rain and small hail may accompany
stronger cells.

Southerly breezes of 25-35 mph will be possible in the Sacramento
Valley Friday afternoon and evening, and again Saturday afternoon.
Southwesterly gusts of 30-50 mph will be possible over exposed
ridges in the mountains.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...

Periods of unsettled weather are expected through the extended
period. By Monday, a wave within the northwest flow will bring
light showers, mainly over the foothills and mountains. Ridging
amplifies Tuesday in wake of exiting wave. Another system will
bring more widespread light to locally moderate rain, moderate
mountain snow, and gusty winds by mid-week. NBM probabilities of
at least 0.25 inches range from 35% to 60% for the Valley, with
60-90% across the northern Sacramento Valley and
foothills/mountains. Snow levels begin around 5000 to 6000 feet
Wednesday, then lower to 3500 to 4500 feet by early Thursday
morning. NBM indicates a 40-70% probability of at least 6 inches,
and a 20-50% probability of at least 12 inches of snow over the
Sierra above 5000 feet through Thursday.

&&

.AVIATION...

Primarily VFR conditions over interior NorCal next 24 hrs. Light
to moderate rain expected to begin in northern Sacramento Valley
around 17z and may impact visibility there. Surface winds will
remain below 12 kts through 16z, then begin to pick up, especially
in the mountains, northern Sacramento Valley, and surrounding
foothills. Sustained winds up to 20 kts, with gusts up to 30 kts
expected in those areas, with sustained winds closer to 10 to 15
kts elsewhere in the Valley and foothills.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from noon Friday to 5 AM PDT Sunday for
West Slope Northern Sierra Nevada-Western Plumas County/Lassen
Park.

Winter Storm Warning from 6 PM Friday to 8 AM PDT Sunday for West
Slope Northern Sierra Nevada.

&&

$$
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