FXUS66 KSTO 112045
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
145 PM PDT Thu Sep 11 2025
SYNOPSIS...
Afternoon/evening shower and thunderstorm chances continue today
and Friday for portions of interior NorCal as a slow moving
weather system exits the region. Near normal temperatures and
drier weather then arrive by the weekend, with above normal
temperatures and periodically breezy and drying north winds
expected by next week.
.KEY MESSAGES...
* TODAY - FRIDAY:
- Scattered showers and thunderstorms are expected across the
northern Sacramento Valley/surrounding terrain and northern
Sierra/southern Cascades today.
- Probability of thunderstorms: 15-30%, highest across Shasta
County mountains
- Probability of Rain > 0.1" : 20-40%, highest across Shasta
County mountains and northern
Sierra/southern Cascades
- Isolated shower/thunderstorm chances along the Sierra crest
south of Interstate 80 on Friday as the weather system exits
the region.
- Probability of thunderstorms: 10-20% along Sierra crest south
of Interstate 80, highest south
of Highway 50
- Probability of Rain > 0.1" : 15-30% along Sierra crest south
of Interstate 80
- Below normal temperatures today warm to near normal on Friday.
Breezy onshore winds continue. Valley high temperatures in the
80s with 60s to 70s at higher elevations.
* SATURDAY - SUNDAY:
- Transient ridging aloft is expected Saturday as the exiting
trough pushes eastward. A progressive shortwave trough then
looks to traverse the Pacific Northwest on Sunday.
- High temperatures in the 80s to low 90s expected at lower
elevations, with 70s to low 80s at higher elevations.
- A slight (5-10%) chance for an isolated light shower/thunderstorm
across Shasta County mountains on Sunday as the shortwave
moves through.
* NEXT WEEK:
- The aforementioned shortwave trough ejects eastward early
Monday, followed rapidly by amplifying ridging. Dry weather and
above normal temperatures anticipated much of next week.
- Increasing north winds expected on Monday as mid/upper level
jet briefly aligns down the Valley. Strongest winds at this
time are anticipated late Sunday night through mid day Monday
in northern/central Sacramento Valley.
- Probability of Wind Gusts > 25 mph: 30-55% for
northern/central Sacramento Valley
-
Areas of Minor to Moderate HeatRisk Tuesday-Thursday, with
Valley high temperatures in the mid to upper 90s and limited
overnight recovery.
.CHANGES FROM PREVIOUS FORECAST...
- Shower/thunderstorm chances linger along Sierra on Friday, with
chances on Sunday continuing to trend down.
- Above normal temperatures and areas of Moderate HeatRisk
expected Tuesday-Thursday.
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