Big River, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

789
FXUS66 KSTO 232141
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
141 PM PST Tue Dec 23 2025

For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.


.KEY MESSAGES...

 - Series of atmospheric rivers will bring major holiday travel
   impacts from periods of heavy rain, heavy mountain snow, and
   gusty winds throughout the week.

 - High snow levels begin falling from late today onward.
   Heaviest snow is expected Wednesday and Thursday, with snowfall
   rates of 1-2" per hour at times.

 - Periods of heavy rainfall are anticipated across the Valley and
   lower foothills with additional flood impacts possible through
   the end of the week.

 - Strong southerly winds expected, with gusts up to 60mph
   Wednesday and Thursday.

&&

.DISCUSSION...

...Today and tonight...

A stream of moisture from the eastern Pacific continues to funnel
into CA today and through the holiday week. Current radar has
precipitation continuing at higher elevations, while a brief lull
in activity is being observed in the Valley. HIRES guidance has
this continuing through the remainder of the afternoon before
heavy precipitation moves onshore and becomes widespread across
the area. Snow levels are sitting around 7000-8000 feet and will
slowly decline as we move into tonight and tomorrow. Southerly
winds will increase as a shortwave moves onshore, with wind gusts
of 40-60 mph overnight and into Wednesday.

...Wednesday through Friday...

Band of heavy precipitation moves on shore late Tuesday into
Wednesday morning. Rain overspread the area, with snow levels
diminishing as colder air filters down aloft. Snow levels drop
toward 4500-5500 feet in the Sierra by the later afternoon and
into the overnight. The Coastal range and southern Cascades will
see snow levels down to 3500 feet later on Wednesday through
Friday. A lull in activity is expected during the day on
Wednesday before another band of stronger precip moves on shore as
the associated low pressure system moves onshore. Rain totals
range between 2 and 5 inches within the Valley, with higher
amounts at higher elevations. Flooding in susceptible urban and
low lying areas, including small streams and creeks from the heavy
rainfall. Embedded thunderstorms may bring higher rainfall rates
at times, like in Shasta county. Remember to turn around and don`t
drown. Find alternative routes and make adjustments to travel
plans if needed to avoid flooded areas. For the Sierra, the
snowfall will range between 4 to 8 feet 5500 feet and above, with
locally higher amounts at the highest elevations. Up to a foot of
snow at 4500-5500 feet. Areas around the Coastal range and
southern Cascades will see 1 to 3 feet above 4500 feet and up to a
foot around 3500-4500 feet.

Low level shear along the frontal boundary moving across the area
brings the chance for isolated strong to severe thunderstorms,
during the later evening and overnight hours on Wednesday. Main
hazards will be gusty winds and small hail, with the low chance of
a tornado.

Wednesday and Thursday we will see strong southerly winds ahead of
the frontal boundaries where wind gusts reach up to 60 mph. A lull
in the strongest winds will be co located to the lull in
precipitation. Winds will remain strong on Thursday before slowly
diminishing by later Thursday and into Friday morning.

Given the magnitude of expected rainfall, mountain snowfall, and
gusty winds, major travel impacts affecting the holiday travel
period are anticipated throughout the week. A combination of
dangerous mountain travel conditions from heavy, wet snow and
gusty winds and periods of difficult travel at lower elevations
from heavy rain, gusty winds, and thunderstorm chances is likely
Wednesday through Friday. If you have travel plans this week plan
ahead, make alternate routes, have backup plans, and carry safety
kits with you in case of an emergency. If you see flooded areas,
turn around don`t drown.

Precipitation lingers Saturday morning in the mountains, with
minor impacts. Otherwise, expect drier conditions over the
weekend and into next week. Chance for low stratus to redevelop
within the Valley over the weekend and early next week.

&&


.AVIATION...

VFR/MVFR conditions expected through 00z, becoming MVFR/IFR in
widespread RA/SHRA after 06z although some LIFR possible at times
in isolated +RA/+SHRA at low elevations. Snow levels 7000-8000 ft
begin dropping to 5500-6500 ft after 09z Wednesday. Once snow
levels fall, LIFR/VLIFR conditions anticipated over mountains in
+SN/+SHSN and gusty winds. Precipitation expected to gradually
clear after 13z Wednesday at TAF sites. Breezy south winds with
gusts 20-25 kts prevail through 00z, then increasing with gusts 35
to 45 kts before becoming breezy again after 13z Wednesday.
Stronger gusts expected along Sierra. Low level wind shear 45 to
55 kts at times between 00z and 12z Wednesday.


&&

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

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

High Wind Warning until 4 PM PST Thursday for Carquinez Strait
and Delta-Central Sacramento Valley-Motherlode-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Southern Sacramento Valley.

&&

$$