271
FXUS66 KSTO 132007
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
107 PM PDT Mon Oct 13 2025

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

.SYNOPSIS...
A wet, cold system will continue to bring widespread rainfall and
the season`s first measurable snowfall to the mountains through
early Wednesday morning. Latest precipitation and snowfall
amounts have trended down.

.KEY MESSAGES...

* TODAY - WEDNESDAY AM:

 - Precipitation coverage and intensity is expected to increase
   later this afternoon as a cold, wet system continues to move
   across the area.

 - A Winter Storm Warning is in effect until 5 AM Wednesday for
   the Sierra Nevada and Lassen NP areas above 6500 feet. Total
   snowfall accumulations of 4-8" are expected along the I-80 and
   Highway 50 corridors, as well as Lassen National Park. 1-2 feet
   of snow are anticipated south of Highway 50, with the heaviest
   late tonight and Tuesday.

 - Widespread Valley and foothill rain is expected today, with
   the heaviest rainfall anticipated later this afternoon into the
   overnight hours. Latest WPC guidance indicates rainfall totals
   of 0.50" to around 1.50" in the Valley and Sierra foothills.
   Highest precipitation totals generally along and south of I-80.

 - Scattered showers are expected on Tuesday, with the potential
   for isolated thunderstorms (10-15% chance). Best thunderstorm
   potential will be over the northern San Joaquin Valley and
   adjacent foothills.

 - Lingering showers through early Wednesday morning, followed by
   drier conditions.

* WEDNESDAY PM - SATURDAY:

 - Dry conditions expected with a gradual warming trend and
   periodically breezy winds. Below to near normal temperatures
   are anticipated, with Valley highs in the 70s.

 - Trough moving through in northwest flow may bring light
   mountain showers on Sunday, but confidence is low.

.AVIATION...

A weather system will continue to impact interior NorCal through
Tuesday, bringing MVFR/IFR/LIFR conditions from rain and mountain
snow. Isolated thunderstorms possible through Tuesday. Snow levels
5500-6500 feet. Gusty southerly winds expected through 06z
Tuesday, with gusts up to 15-25 kts in the Valley and Delta and up
to 20-30 kts over the mountains. Gusty and erratic winds near
thunderstorms.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 5 AM PDT Wednesday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$