783
FXUS66 KSTO 112045
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
145 PM PDT Thu Sep 11 2025

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

.DISCUSSION...

.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.

&&

.AVIATION...
Periods of MVFR/IFR possible in scattered showers/thunderstorms
generally in the mountains north of Interstate 80 through 07z
tonight. Highest thunderstorm chances are in the northern Coast
Range, Shasta County mountains, and Sierra/southern Cascades, with
the potential for isolated thunderstorms to spread into the
northern Sacramento Valley in the vicinity of KRDD around 03-06Z.
Otherwise, primarily VFR conditions anticipated elsewhere. SCT-BKN
marine stratus could affect the Delta and Sacramento metro area
12-17z Friday morning.

&&

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

$$