Big River, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

000
FXUS66 KSTO 202153
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
153 PM PST Sat Dec 20 2025

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


.KEY MESSAGES...

 - Light rain and high elevation snow showers today, with
   widespread precipitation this evening and overnight.

 - Series of atmospheric rivers will bring widespread moderate to
   heavy precipitation Sunday through the holiday week.

 - High snow levels through the early week, gradually falling
   through mid week, with potential major holiday travel impacts
   over the passes.

 - Period of gusty southerly winds through mid week, with the
   strongest Sunday and Wednesday.

&&

.DISCUSSION...

...Today and Tonight...

Current satellite and radar shows isolated to scattered rain
showers moving through the Coastal range and Bay Area into the
Valley. Rain will continue to spread eastward through today, with
widespread chances this evening and overnight. Snow levels are
over 8000 feet today and into Sunday. Higher elevation snow
showers are likely. Winds will begin to increase out of the south
through the overnight hours, with gusts up to 30mph at times
within the Sacramento Valley and northern San Joaquin Valley.
Minor impacts from snow and rain through the remainder of today
and into tonight.

...Sunday through Friday...

Satellite shows the swath of precipitable water moving through
the eastern Pacific and entering CA. This strong push of moisture
is associated with a deepening trough across the eastern Pacific.
This will bring a moderately strong atmospheric river, with
several rounds of precipitation and gusty southerly winds to the
forecast region Sunday through the holiday week.

Heavier rainfall is expected to develop and push through northern
CA Sunday, with snow levels remaining above 8000 feet, with only
light snow expected at the higher peaks. Isolated thunderstorms
(15-25 percent) Sunday afternoon and evening across portions of
the Sierra and northern Sacramento Valley. Gusty southerly winds
are expected within the Sacramento Valley and portions of northern
San Joaquin Valley Sunday. Probabilities of seeing over 40 mph
wind gusts are 70-80 percent along the foothills of the Sierra
(north of I-80) and in the northern Sacramento Valley. Thus a Wind
Advisory is in effect 4am through 10pm Sunday.

Rain will continue to be moderate to heavy at times through the
week, with the heaviest totals in the higher terrain of Butte
county where 10 inches is around 90 percent of occurrence.
Elsewhere, 3 to 8 inches of rainfall looks likely, with the lower
amounts within the Valley. An Areal Flood Watch is in effect at
4pm Today and continues through 4pm next Saturday for urban, small
streams and creek flooding.

Snow levels begin to drop early to mid week, with levels around
5500 feet Tuesday evening through Friday. Probabilities of seeing
over 30 inches of snow is 70 to 80 percent above 5500 feet.
Once it gets closer we will get more exact amounts in the
forecast as snow level fluctuations often occur with these
systems but several feet of snow seems likely. A Winter Storm
Watch is in effect Tuesday evening through Friday morning for
areas above 5500 feet. Lastly, winds will be breezy out of the
south mid week, with probabilities of over 45mph being 40-60
percent in the foothills and over 60 percent in the mountains.

Holiday travel impacts are likely as this atmospheric river sets
up and affects the forecast area. Lingering impacts are likely
after Christmas and into the early portions of next weekend.
Monitor the latest forecasts, have backup plans for travel, and
watch for flooded roadways this Holiday week.

&&


.AVIATION...

Ceilings remain IFR to MVFR through the TAF period, with rain
chances increasing throughout the day. Visibilities remain MVFR
through the period, with occasional VFR at times outside of rain.
Heaviest rain is expected to move in around 23-02z and continue
through the overnight period. Around 13-15z rain will be moderate
at times through the end of the TAF period. Winds will be on the
increase out of the south around 10-15kts, with gusts up to 25kts
07z through the end of the TAF period. Winds will be strongest
Sunday afternoon and evening for areas north of I-80, with some
areas seeing 30kt to 35kt gusts.

&&

.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.

Wind Advisory from 4 AM to 10 PM PST Sunday for Central
Sacramento Valley-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley.

Winter Storm Watch from Tuesday evening through Friday morning
for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$