698
FXUS66 KSTO 302002
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
102 PM PDT Fri Oct 30 2026

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


.KEY MESSAGES...

 - Light rain and mountain snow showers continue today for the
   Sierra and surrounding areas, accompanied by a low chance of
   isolated thunderstorms this afternoon into early evening

 - Cooler temperatures, rain and mountain snow above 7,000 feet
   Saturday into Sunday

 - Winter Weather Advisory in effect from 8 AM Saturday to 7 AM
   Sunday for elevations above 7000 feet in the Sierra Nevada

 - Drier and warmer conditions Sunday through early next week, but
   temperatures will remain below-normal for this time of year


&&

.DISCUSSION...

A slow moving weak cold front is traversing Northern California
today. As of 11AM, isolated light rain and mountain snow showers
continues over portions of the Sierra. Shower activity will
continue this afternoon with mix rain and snow over the Sierra,
with spotty rain showers in the vicinity. There is a low chance of
isolated thunderstorms, capable of and brief heavy downpours this
afternoon into early evening. Generally dry weather is expected
for much of the forecast area through today.

Increasing chances of precipitation is expected tonight and
Saturday as a broad and deep upper low centered in the Northeastern
Pacific and a low in the Eastern Pacific interact and shift
eastward across the region through Sunday. Precipitations amounts
have been trending slightly higher over the Sierra with this
system, especially south of I-80 where up to 2.5 inches of rain
is expected. The 00Z ECMWF Extreme Forecast Index highlight
50-70th percentile above normal QPF for portions of the Sierra
south of I-80. Most likely rain total amounts range 0.5 to 2.5
inches over the mountains and 0.2 to 1 inch for foothills, with
the highest amounts in the Sierra foothills. Meanwhile, lighter
amounts ranging from a trace to 0.2 of an inch are expected for
the Valleys and Coast Range, with the highest amounts in Shasta
and eastern Modesto counties.
Colder air aloft will bring an increasing instability on Saturday,
capable of produce brief heavy downpours and a chance of isolated
thunderstorms. Snow levels are expected to be above 7000 feet on
Saturday, lowering to 6000-7000 feet Saturday night into Sunday.
The snowfall total amounts are also trending higher with this
system over portions of the Sierra Nevada, with the heaviest
snowfall amounts expected above 7000 feet. Total snow accumulations
up to 10 inches, with up to 25 inches at the highest peaks. Minor
accumulations of up to 3 inches possible down to 6000 feet. Some
light flurry will be possible as low as 5000 feet, but no snow
accumulation are expected below 6,000 feet. A Winter Weather
Advisory is now in effect from 8 AM Saturday to 7 AM Sunday for
Northern Sierra above 7000 feet, including Highway 50 and
Interstate 80.

High pressure build in in the wake of the trough on Sunday.
Resulting in drying and modest warming Sunday through early next
week. Breezy to east northerly winds are expected to developed
across the area, with the strongest winds over the Sierra.
Clusters are showing another upper-level trough approaching the
area Tuesday, but there is a lot of uncertainty in the timing and
position of this system.

&&

.AVIATION...

VFR conditions prevail across interior NorCal next 24 hours.
Surface wind gusts generally below 12 knots across Valley TAF
sites through 20z Saturday, when occasional gusts up to 20 kts
can be expected in teh northern Sacramento Valley, adjacent
foothills, and in the mountains. Low to mid-level clouds will
continue through Saturday, slightly lowering ceilings at TAF
sites. Light Valley rain showers possible, with chances increasing
late Saturday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 AM Saturday to 7 AM PDT Sunday
for Sierra (Cal-Tuo) Above 5000 ft-Sierra (El Dorado-Amador)
Above 5000 ft-Sierra (Sierra-Placer) Above 5000 ft.

&&

$$