968
FXUS66 KSTO 152029
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
129 PM PDT Sat Mar 15 2025

.SYNOPSIS...
Snow showers are possible over the mountains today, with
accumulating snow over the Shasta County mountains. Sunday into
Monday, expect more widespread mountain snow with periods of
moderate to major travel impacts expected. Strong gusty winds are
expected, especially for the northern Sacramento Valley and
northeast foothills.
&&

.DISCUSSION...
Current radar analysis reveals mostly light snow showers present
in the Shasta County mountains this afternoon. Activity is
expected to increase in coverage in the aforementioned mountains
later this afternoon and continue throughout the evening and
overnight hours.  A Winter Storm Warning has been issued for
elevations above 4000 feet for Shasta County from 11 AM this
morning through 11 PM Sunday, with 6 to 12 inches of snow
accumulation and up to 2 feet over peaks. Some light rain showers
may extend into the northern and central Sacramento Valley today,
with generally dry conditions farther south. High temperatures
this afternoon will remain about 6 to 12 degrees below normal.

Our next widespread winter storm system arrives Sunday and
continues through early Tuesday bringing more rain, mountain
snow, and strong southerly winds. Strong winds aloft are forecast
to mix down to the surface, with ensembles showing the potential
for 65 mph gusts (60-80% probability) over the northeastern
foothills, with gusts up to 50 to 60 mph (50-70% probability) over
the northern Sacramento Valley. A High Wind Warning continues for
the area from 11 PM Sunday until 11 PM Monday. A Wind Advisory
continues for the Central Sacramento Valley, portions of the
southern Sacramento Valley, and adjacent foothills for gusts 40 to
50 mph, also from 11 PM Sunday until 11 PM Monday. Ensemble
guidance continues to show high probability of heavy snow in the
southern Cascades and northern Sierra. A Winter Storm Warning has
been issued for above 4500 feet for the southern Cascades from 11
AM Sunday to 11 PM Monday, and from 5 PM Sunday to 11 PM Monday
for the northern Sierra. Snowfall amounts of 1 to 2 feet are
expected, with up to 3 feet over higher peaks. Around 6-10 inches
of snow is expected for elevations between 4500-5000 feet. This
could bring moderate to major mountain travel impacts. Afternoon
thunderstorms are possible in clearing behind a cold frontal
passage, with best potential over the eastern Valley and into the
foothills.

 Latest probabilities moving into next week are as follows:

Probability of Rain > 1" Late Sunday-Tuesday AM: 30-60%
Valley/foothills, highest probs in the northern Sacramento Valley
and foothills.

Probability of Snow > 12" Late Sunday-Tuesday AM: 70-95% above
4500`

Probability of Thunderstorms Monday: 20-30%

It continues to look like most precipitation is expected to be
coming to an end by very early Tuesday morning. Dry weather is
expected for the rest of the day, with cold morning temperatures.
The NBM projects near freezing for the northern Sacramento Valley,
mid to upper 30s for the rest of the Valley, with areas of
morning frost possible.
&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...


A brief lull widespread activity is expected early Wednesday, then
another PacNW trough is progged to dig into Oregon and Washington,
which will slightly lower our heights and also re-introduce a shot
of light precipitation for the region Wednesday night and into
Thursday. Cluster analysis is relatively confident that most of
the heavier precipitation impacts will remain north of our CWA.
As that trough exits to our east on Thursday afternoon, ensembles
are depicting another shortwave trough strengthening in the PacNW
which will help keep our heights mostly flat, and allow for
additional moisture to return to the area Friday and Saturday. As
of now, most of the precipitation will be focused on portions of
the northern Sacramento Valley, southern Cascades, and the Sierra.
Slight changes in the trough`s intensity will alter the forecast,
however Clusters are confident in this general flat, zonal height
pattern. High temperatures will generally be in the low to mid
60s in the extended forecast period, with cooler 40s to mid 50s
for our higher elevations.
&&

.AVIATION...

Mostly VFR conditions across the Valley today, except in the
northern Sacramento Valley where MVFR/IFR conditions may develop
from a weather system moving through the area, bringing light rain
showers and snow showers to the Shasta County mountains. Strong
southerly winds are expected to develop tomorrow around 06z
Sunday and continue Sunday night, with southerly gusts up to
around 50 kts along the I-5 corridor north of Chico. Elsewhere,
gusts up to 40 knots will be possible in the central/southern
Sacramento Valley and Delta. Mountain wind gusts up to 60 knots
are also expected.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 11 PM PDT Sunday for Shasta Lake Area
/ Northern Shasta County-West Slope Northern Sierra Nevada-
Western Plumas County/Lassen Park.

High Wind Warning from 11 PM this evening to 11 PM PDT Sunday
for Northeast Foothills/Sacramento Valley-Northern Sacramento
Valley.

Wind Advisory from 11 PM this evening to 11 PM PDT Sunday for
Central Sacramento Valley-Motherlode-Mountains Southwestern
Shasta County to Western Colusa County-Southern Sacramento
Valley.

&&

$$