Arnold, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

448
FXUS66 KSTO 111903
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1203 PM PDT Sat Apr 11 2026

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


.KEY MESSAGES...

 - Active weather will continue through the weekend with showers, heavy
   mountain snow, gusty winds, and thunderstorms.

 - Winter Storm Warning in effect for the Sierra and Southern
   Cascades through Sunday evening.

&&

.DISCUSSION...

...This Weekend...

Upper level trough continues to move onshore this weekend
bringing showers, heavy mountain snow, gusty winds, and
thunderstorms to the area. Current satellite has the center of the
low offshore of CA. Surging moisture and instability ahead of the
low pressure is helping fuel showers and mountain snow over CA.
Current radar has isolated to scattered shower activity through
the Valley and foothills with scattered snow in the mountains
around 6000-7000 feet and above. Latest 12z guidance from the CAMS
show a timeframe of 20-22z for storms to develop along the
western side of the forecast area and track NE to north through
the afternoon and evening hours. Atmospheric profiles show
500-1000 J/kg CAPE, sufficient low level moisture/shear, and long
skinny CAPE profiles within the Valley. This brings the chance
for 1+ inch hail, strong winds, accumulating hail, funnel
clouds/brief weak tornadoes, and locally heavy rainfall rates.
Stay alert and stay prepared by having a way to receive watches,
warnings, and statements this afternoon and evening.

Winds will be strong out of the south this afternoon and evening,
with gusts of 35-45 mph within portions of the northern
Sacramento Valley, northeastern Foothills, and into portions of
the southern Sacramento Valley. We will continue to monitor for
any headline potential for winds this afternoon and evening for
the Sacramento Valley and adjacent foothills.

The center of the low pressure system moves onshore Sunday
bringing further chances for thunderstorms. Soundings look near
the same as they do for today across the Valley. As the Low
pressure moves through, colder air shifts down, which could bring
a slightly increased chance for cold air funnels to the area
during the day on Sunday. We will continue to monitor the latest
trends in the forecast and environmental conditions for Sundays
thunderstorm impacts and any chance for cold air funnels.

Through today and tomorrow snow levels will continue to drop as
the low moves through. Snow levels today will be around 6000-7000
feet and lower toward 4000-5000 feet by Sunday. Latest HREF
guidance has probabilities of 50-60 percent to see 1-2 inch per hour
snowfall rates this afternoon through Sunday. Heavy snow is
expected, and a Winter Storm Warning is in effect through Sunday
at 11PM. Total snow accumulations 1 to 2 feet above 4500 feet,
with up to 3 to 4 feet at the highest peaks. Minor snowfall
accumulations of 2 to 4 inches down to 4000 feet. Wind gusts as
high as 50 mph. Travel could be very difficult to impossible this
weekend within the mountains.

... Next Week...

A return to drier and warmer temperatures early to mid next week
as a ridge of high pressure builds into the region. Signal is
there for brief showers and snow showers Wednesday as a system
moves north of the area, but confidence remains low on development
and track of the system.

&&

.AVIATION...

MVRF conditions, with periods of IFR in and around thunderstorm
activity for the TAF period. Thunderstorm chances increase this
afternoon and evening and continue into the overnight hours. Winds
may be erratic with direction and speed in and around
thunderstorm activity. Otherwise, surface winds will be strong out
of the south, with gusts up to 40kts at times in the northern
Sacramento Valley this afternoon and evening. Winds slowly
diminish overnight and into tomorrow, but remain breezy at times.
Further thunderstorm chances tomorrow afternoon and evening.


&&

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

&&

$$