Flash Flood Warning 1, NWS Sacramento, CA

Area Forecast Discussion
National Weather Service Sacramento CA
221 PM PDT Tue Sep 9 2025

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

.DISCUSSION...

.SYNOPSIS...
Active weather and cooler temperatures continue this week as a
slow moving system brings scattered shower and isolated
thunderstorm chances through Thursday. A brief return to near
normal temperatures and drier weather is expected Friday and
Saturday, with a quick moving system then looking to move through
late weekend into early next week.

&&

.KEY MESSAGES...

* TODAY - THURSDAY:
 - Periods of scattered showers and embedded thunderstorms are
   expected through much of the week ahead as longwave troughing
   moves onshore, briefly stalls over interior NorCal on
   Wednesday, then ejects eastward on Thursday.

 - Highest thunderstorm chances today across the northern
   Sacramento Valley/surrounding terrain, expanding to include the
   Sierra/southern Cascades on Wednesday, then shifting to the
   Sierra crest by Thursday.

 - Slight chances for showers/thunderstorms exist through the
   remainder of the Valley/foothills, with highest potential,
   around 10-20%, on Wednesday.

 - Today:

   - Probability of thunderstorms: 20-30% across northern Sacramento
                                   Valley/surrounding terrain
   - Probability of Rain > 0.1"  : 60-80% across northern
                                   Sacramento Valley/surrounding terrain,
                                   20-40% elsewhere

 - Wednesday - Thursday:

   - Probability of thunderstorms: 25-45% chances on Wednesday for
                                   northern Sacramento Valley/surrounding
                                   terrain & Sierra/southern Cascades
                                   15-25% chances on Thursday for
                                   northern Sacramento Valley/surrounding
                                   terrain & Sierra/southern Cascades
   - Probability of Rain > 0.1"  : 30-60%, highest along the Sierra/
                                   southern Cascades, Coastal Range,
                                   and Shasta County mountains.

 - Nocturnal showers/thunderstorms remain possible tonight
   through Wednesday morning for portions of the northern
   Sacramento Valley and surrounding terrain.

 - 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.

* FRIDAY - SUNDAY:
 - As the longwave trough exits the region, a period of drier
   weather is expected to start the weekend with near normal
   temperatures returning.

 - High temperatures in the mid to upper 80s expected at lower
   elevations, with 70s to low 80s at higher elevations.

 - A progressive weather system is expected to move through the
   region Sunday, bringing a slight chance for showers/isolated
   thunderstorms, primarily to the northern Sacramento
   Valley/surrounding terrain.

.CHANGES FROM PREVIOUS FORECAST...
- Slight increase in thunderstorm chances for Wednesday, still
  focused across the northern Sacramento Valley/surrounding
  terrain and Sierra/southern Cascades.
- Forecast rainfall amounts continue to trend lower for most
  Valley locations outside of the northern Sacramento Valley.

&&

.AVIATION...
Generally VFR conditions expected at TAF sites. Breezy winds
continue, with gusts to 15-30 kts at times. Chances for local
MVFR/IFR conditions from showers or thunderstorms over the
northern Sacramento Valley and Shasta County mountains into
Wednesday.

&&

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