034
FXUS66 KSTO 192054
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
154 PM PDT Mon Oct 19 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Chance for a shower over the Coastal Range this
afternoon/evening.
- Widespread precipitation Tuesday through Thursday, with below
normal temperatures, thunderstorm chances, and high elevation
snow showers.
- Dry conditions return end of the week and into the weekend,
followed by the potential for further unsettled weather.
&&
.DISCUSSION...
...Today through Thursday...
Current satellite and radar has an area of light showers over the
Coastal Range this afternoon as a trough sits off the coast. This
trough will continue to deepen and move onshore through
Thursday. Today we will continue to see clouds move into the
region with a broken cloud deck overnight. Temperatures will be in
the upper 60s to lower 70s today and through the remainder of the
week.
The main push of precipitation comes Tuesday evening as moisture
from the south pushes through California. Snow levels will be
above 9000 feet on Tuesday and drop to 8000-9000 feet Wednesday.
Tuesday evening, we will see instability increase across the
mountains and foothills, with up to 500 J/kg of CAPE and strong
speed and directional shear. This fuels the chances for an
isolated thunderstorms within the mountains and foothills. A few
storms may be on the stronger side with small hail, gusty winds,
and frequent lightning possible. As we move through Tuesday night
into Wednesday precipitation chances becomes widespread across the
forecast area, with increased chances for thunderstorms by
Wednesday afternoon in parts of the southern Sacramento Valley,
northern San Joaquin Valley, foothills, and mountains. Shear,
instability, moisture, and lift are in better positions to
initiate and sustain thunderstorms Wednesday afternoon/evening. A
few storms may be on the stronger side Wednesday, with small hail,
gusty winds, brief heavy rain, and frequently lightning being the
main hazards. There is a low chance for a low top supercell to
develop within the foothills and/or northern San Joaquin Valley
where shear is more elongated and sustainable for supercellular
development. We will continue to monitor the latest for
thunderstorms Tuesday and Wednesday.
Snow levels start to drop to the 8000-9000 feet Wednesday, and a
few inches are possible within the higher peaks of the Sierra
predominantly south of Highway 50. Minor impacts are possible in
eastern Tuolumne and Alpine counties Wednesday and potentially
into Thursday as the system lingers across the area. Thunderstorm
chances will again be possible Thursday, but remain in the
foothills and Sierra where lift is more sustainable for the growth
and development.
...Friday and onward...
The system moves out of the southwestern United States Friday and
Saturday, with a return to dry conditions for the area. This
doesn`t last long as ensemble guidance continues to show an
unsettled pattern redeveloping across the western United States
bringing the potential for more precipitation to parts of
California. Temperatures during this time remain below average for
this time of year. Uncertainty arises with the development,
timing, and strength of any precipitation end of the weekend and
into next week.
&&
.AVIATION...
VFR conditions prevail across the region through the TAF period.
There are some brief low clouds around the RBL site this morning,
which will continue off and on through 19z. Otherwise, winds will
be breezy at times, with a few gusts near the Sacramento sites to
20kts this afternoon/evening. Overnight clouds move in for all
sites from the west as a system moves into the region.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
