383
FXUS66 KSTO 072000
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
100 PM PDT Sun Sep 7 2025

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

.DISCUSSION...

.SYNOPSIS...
Seasonable and dry weather today transitions to a period of
cooler temperatures and more active weather into the week ahead as
a slow moving system affects the region. Daily shower and
isolated thunderstorm chances are expected Monday-Thursday, with
highest chances across the northern Sacramento Valley and over the
mountains. A brief trend toward near normal temperatures and
drier weather then looks to follow late week into next weekend.

&&

.KEY MESSAGES...

* TODAY:
 - Seasonable temperatures continue today alongside breezy
   onshore winds and steadily improving humidity recovery.

 - A slow moving longwave trough currently deepening offshore will
   continue a gradual eastward progression this evening into the
   week ahead.

* MONDAY - THURSDAY:
 - Periods of scattered showers and embedded thunderstorms
   expected through much of the week ahead as the aforementioned
   longwave trough moves onshore, and briefly stalls over interior
   NorCal on Wednesday.

 - Highest thunderstorm chances across the northern Sacramento
   Valley/surrounding terrain Monday and Tuesday, expand to
   include the Sierra/southern Cascades Wednesday and Thursday.

 - Lower, but still nonzero chances for showers/thunderstorms
   through the remainder of the Valley/foothills on Wednesday.

 - Monday - Tuesday:

   - Probability of thunderstorms: 20-30% across northern Sacramento
                                   Valley/surrounding terrain
   - Probability of Rain > 0.1"  : 60-80% for northern Sacramento
                                   Valley/surrounding terrain,
                                   25-45% elsewhere

 - Wednesday - Thursday:

   - Probability of thunderstorms: 20-40% chances on Wednesday for
                                   northern Sacramento Valley/surrounding
                                   terrain
                                   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

 - While some uncertainty around timing/magnitude still persists,
   highest chances for nocturnal showers/thunderstorms is expected
   overnight Monday-Tuesday AM and overnight Tuesday-Wednesday AM.

 - 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...
- Highest shower/thunderstorm chances trending toward northern
  Sacramento Valley/surrounding terrain and Sierra/southern
  Cascades.
- Still some uncertainty in lingering shower/thunderstorm
  potential on Thursday.

&&

.AVIATION...
Generally VFR conditions expected at TAF sites through Monday
morning, although a 30-60% chance of MVFR/IFR in low stratus is
possible across the Delta and Sacramento Valley 10z-16z Monday.
Breezy winds continue, with gusts 15-25 kts at times. Strongest
winds expected 18z Monday - 06z Tuesday through the Delta and
adjacent Valley locations, as well as the Sierra. Chances for
local MVFR/IFR conditions from showers or thunderstorms over the
northern Sacramento Valley and Shasta County mountains Monday
afternoon into the overnight hours.

&&

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

$$