563
FXUS66 KSTO 282013
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
113 PM PDT Wed Oct 28 2026

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


.KEY MESSAGES...

 - Cool and mostly dry weather through Friday

 - Pattern change to unsettled weather Saturday into Sunday, with
   rain and mountain snow above 6000-7000 feet

 - High pressure will promote a drying and modest warming for
   Sunday and Monday

 - Breezy north to east winds Sunday into Monday


&&

.DISCUSSION...

...Today through Friday...

Cool and mostly dry weather pattern with light winds is expected
to persist across northern interior California through Friday.
Although, a weak surface high pressure is promoting a modest
warming today. Afternoon highs in the mid 60s into low 70s for the
Valleys, 55-65 in the Foothills and 50s-60s in the mountains
today. Cold morning lows are expected for the mountains and
higher elevation basins the next few days, with near to below
freezing temperatures. Patchy fog or haze will be possible each
morning in the Valley.

A larger upper-level trough is expected to deepen offshore
Thursday and Friday, with a series of embedded weak shortwave
moving across the area. This will bring a slight chance of
isolated mountain showers over the Sierra. Elsewhere, will see
mostly increasing mid to high clouds.

...Saturday through Tuesday...

A system will moves across the area Saturday into Sunday bringing
an increasing chance of rain and mountain snow above 6000-7000
feet. Uncertainties remain on how much moisture will arrives
across the area, as well on the exact amounts. There is a near 50%
chances of measurable rain (0.01") for the Valley, with higher
chances across the eastern portions of the forecast area. The
chance for wetting rain (0.10") is 20-45% for the Valley, with the
highest chances in Stockton and Modesto counties. While the
models tend to agree that the higher rain chances will occur over
the Sierra Foothills and mountains. The 25th percentiles shows
0.1-0.4 inches over the Sierra mountains Saturday into Sunday, the
75th percentile range 0.75-1 inch and the 90th percentile showing
1.5-2 inches. The Sierra foothills have a 90th percentile of
0.8-1.5 inches of rain throughout Sunday. As for the Valleys,
90th percentiles between 0.1 to 0.5 inches for the Sacramento
Valley and 0.7 to 1 inch for the northern San Joaquin Valley.

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.
There is a 35 to 60% chances of snowfall exceeding 3 inches for
the higher terrain over the Sierra Saturday into Sunday,
especially south of the US-50.

Ensemble cluster shows a ridge building in right after the trough
exits 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.

&&

.AVIATION...

VFR conditions prevail across interior NorCal next 24 hours.
Surface wind gusts generally below 12 kts. Low probabilities of BR
developing around 10z Thursday at the northern San Joaquin Valley
TAF sites.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$