166
FXUS66 KSTO 121028
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
228 AM PST Wed Feb 12 2025

.SYNOPSIS...
Another cool and dry morning ahead a weather system bringing
moderate to heavy rain and snow and gusty winds Wednesday night to
Friday.

&&

.DISCUSSION...
Radar imagery this evening is beginning to show the first line of
radar returns as moisture makes it way towards NOrthern CA.
Things will remain relatively quiet throughout the morning with
most precipitation falling as virga and just across the far
southwestern corner of the CWA. Precipitation moves into Interior
Northern CA this evening over the western side of the Valley and
track westward throughout the Thursday early morning. Thursday
morning will be the wettest period, first in the Valley then by
late morning over the Sierra. Snow and rain rates begin to taper
down THursday night into Friday morning with most precipitation
over by very early Saturday morning. Here is look into impacts
during this stretch of weather....

Beginning with snow, snow level Wednesday night will be 1500-2500
feet over Shasta County/Coast Range areas with 3000-4500 feet over
the Sierra mountains. Increasing snow levels move in from the
south and by Thursday morning be 3500-5000 feet over Northern
Shasta and 5000-7000 feet across the Sierra. By the evening much
of Northern CA will see 4500-5500 feet before lowering to around
4000-5000 feet Friday morning. This will bring periods of moderate
to heavy snowfall with feet of snow expected for the Sierra above
4500 feet and up to a foot for the Northern Shasta County areas
above 2000 feet. Additionally, there continues to a chance of snow
across the lower elevations of the Northern Sac. Valley with EC
and GFS Ensembles showing snow accumulations as low as Redding
although is a high level of uncertainty, combined by the
potential mitigating affect of snow falling on rain and/or there
being a mix of rain and snow. Local effects could really come into
play and in areas where cold air can be trapped may see snow but
locally warmer areas see rain or mixed precipitation. No matter
what, plan for slippery road conditions and travel delays as the
weather system moves through.

With all that being said, Winter Storm Warnings remain in effect
for Northern Shasta County/Coast Range above 2000 feet from 10 PM
Wednesday to 4 AM Friday for 3-8 inches with 1-2 feet above 3500
feet and winds up to 45 MPH. For the Sierra and Southern Cascades,
our Warning will be from 10 PM Wednesday to 10 PM Friday for 2-5
feet possible above 6000 feet and 5-15 inches between 4500-6000
feet and winds as high as 60 MPH. Very difficult travel
conditions with chain controls and road closures are expected and
heaviest snowfall is expected on Thursday with rates of 1-2
inches per hours at times.

Widespread rain will impact interior NorCal over the same
timeframe. The NBM shows a 60-90% probability of 1 inch of rain
or more in the Valley with a 60-90% probability of 2 inches or
more in the foothills . Rain may be moderate to heavy at times,
creating slick roads, mud/rock slides in the foothills, high flows
on area waterways and minor flooding issues. There is also a 10
to 20 percent probability of isolated thunderstorms Thursday
afternoon through Friday that could lead to locally heavier rain
amounts. A Flood Watch has been issued for elevations below the
primary snow line to address these conditions.

Gusty southerly winds are forecast with this system, generally
around 30 to 50 mph gusts in the lower elevations Wednesday night
through early Friday, strongest on Thursday. A Wind Advisory has
been issued for portions of the Valley to address impacts such as
difficult driving conditions for high profile vehicles, potential
power outages, downed trees or tree branches, and loose objects
blowing around.

Saturday looks to be mostly a transition day after the mid week
storm tapers off and we see a brief break in precipitation.
Saturday evening will see light showers move ocer the Northern
Sac. Valley and Southern Cascades are with 25-55% of seeing
precipitation.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...

Ensemble guidance then indicates by Sunday morning another
weather system has pushed its wave into the Northern CA, mainly
over the mountains and N. Sac. Valley. This system looks much
weaker than the upcoming mid- week storm, and appears to be more
progressive as well. Little to no impacts are expected from this
weekend storm, with just some dusting of snow, light showers, and
locally breezy winds. On Monday, as any lingering precipitation
tapers off, it appears we can expect a return to drier and
slightly warmer weather that continues into Tuesday.
&&

.AVIATION...

VFR conditions expected to prevail through 00z Thursday, when a
storm system brings widespread MVFR conditions and periods of
IFR/LIFR due to moderate to heavy precipitation. Heavier precip
rates expected to start after 06z Thursday. Snow levels start
around 1000` to 2000` with start of precip in Shasta County and
southern Cascades before rising to 3500` to 4500` over Thursday
(2500` to 4500` in the Sierra, rising to 4500` to 6000`).
Southerly surface winds across the Valley, around 10 to 20 kts,
with gusts 30 to 45 kts at times, starting after 06z Thursday.
South to southwesterly gusts in the Sierra 60 to 70 kts after 06z
Thursday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from this evening through Friday evening for
Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-
Mountains Southwestern Shasta County to Western Colusa County-
Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-
Shasta Lake Area / Northern Shasta County-Southern Sacramento
Valley-West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

Winter Storm Warning from 10 PM this evening to 4 AM PST Friday
for Mountains Southwestern Shasta County to Western Colusa
County-Shasta Lake Area / Northern Shasta County-West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

Wind Advisory from 10 PM this evening to 10 AM PST Friday for
Carquinez Strait and Delta-Central Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Southern
Sacramento Valley.

&&

$$