110
FXUS66 KSTO 062038
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
138 PM PDT Sat Sep 6 2025

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

.DISCUSSION...

.SYNOPSIS...
Largely seasonable weather this weekend transitions to a cooler
and more active weather pattern moving into the week ahead as a
slow moving weather system impacts the region. Breezy onshore
winds persist, with shower and thunderstorm chances Monday-
Thursday. A brief period of warmer and drier weather looks to
follow late next week into the following weekend.

&&

.KEY MESSAGES...

* TODAY-SUNDAY:
 - Seasonable temperatures continue through the weekend alongside
   breezy onshore winds. High temperatures in the mid to upper
   80s, with 70s expected at higher elevations. Despite mostly
   dry conditions, steadily improving humidity recovery
   anticipated from onshore flow.

 - As a progressive offshore shortwave approaches this
   afternoon/evening, a slight (15%) chance of thunderstorms
   remains in place across northwestern portions of Shasta County.

 - A slower moving longwave trough developing offshore will then
   gradually near the region late Sunday. Low (5%) chance for
   northern Sacramento Valley showers late Sunday, with more
   appreciable impacts to interior NorCal much of next week.

* MONDAY - THURSDAY:
 - Appreciable precipitation chances expected through much of the
   week ahead as the aforementioned longwave trough deepens, moves
   onshore, and briefly stalls over interior NorCal.

 - Monday - Tuesday:
   - Probability of thunderstorms: 20-30% across northern Sacramento
                                   Valley and surrounding terrain
   - Probability of Rain > 0.1"  : 40-70% for northern Sacramento
                                   Valley and surrounding terrain,
                                   20-40% elsewhere

 - Wednesday - Thursday:

   - Probability of thunderstorms: 25-35%, highest chances on Wednesday
                                   region-wide, with chances shifting to
                                   Sierra/southern Cascades on Thursday.
   - Probability of Rain > 0.1"  : 30-60%, highest along the Sierra/
                                   southern Cascades

 - Some uncertainty still exists with respect to timing and magnitude
   of expected precipitation.

 - Well below normal temperatures and breezy onshore winds
   expected. Valley low temperatures in the mid 70s to low 80s
   with 60s to 70s anticipated at higher elevations.

.CHANGES FROM PREVIOUS FORECAST...
- Shower and thunderstorm chances increasing for much of the week
  ahead.
- Some overnight thunderstorms possible, but timing and location
  remain highly uncertain.

&&

.AVIATION...
Generally VFR conditions expected at TAF sites next 24 hours,
although a 20-40% chance of MVFR/IFR in low stratus is possible
across the Delta and Sacramento Valley 10z-15z Sunday. Breezy
south to west winds continue, with gusts 15-25 kts at times.
Strongest winds expected 22z-06z through the Delta and adjacent
Valley locations.

&&

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

$$