219
FXUS66 KSTO 292040
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
140 PM PDT Mon Sep 29 2025

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

.SYNOPSIS...
Cooler temperatures with widespread wetting rain early through the
middle of this week across interior NorCal, with the highest
chances within the Coastal Range, southern Cascades, and northern
Sierra. Drier and warmer conditions heading into next weekend with
chances for breezy northerly winds.

&&

.KEY MESSAGES...

*  TODAY THROUGH WEDNESDAY:

 - Low pressure is moving into the area tonday, bringing chances
   for areas of wetting rain through Wednesday. Highest totals
   will be over the mountains.

 - This afternoon and evening also sees a 10-50% chance for
   thunderstorms across interior NorCal, with highest chances in
   the foothills and along the Sierra Crest (generally 30-50%).
   Non- zero chance for convection to continue into the overnight
   hours.

 - The overall trend in precipitation totals has trended down once
   again, with most of the Valley seeing minimal, if any,
   precipitation with this first wave, and less than a quarter of
   an inch with the second.

 - 72 hour probabilities (Monday - Wednesday):
- 5-25% chance of a half inch of rain or more in the central and
      southern Sacramento Valley, and northern San Joaquin Valley
- 40-65% chance in the northern Sacramento Valley
- 45-80% chance of 0.5 inch or more of rain in the mountains

* THURSDAY THROUGH SUNDAY:

 - Lingering showers are possible Thursday morning, though there
   is still some uncertainty in the timing of the end of this
   system and any totals for Thursday. Latest guidance has shown
   precipitation tapering off in the morning.

 - Slight chances (10-20%) on Thursday and Friday afternoons and
   evenings for isolated thunderstorms along the Sierra Crest,
   primarily south of I-80.

 - Friday sees a return to dry weather and a slight warming trend
   into the weekend, with daytime highs reaching closer to
   normal.

 - Breezy northerly winds expected periodically Friday through
   Sunday, strongest on Sunday.

.AVIATION...
VFR to MVFR conditions in the Sac Valley due to frontal system
moving through today. Showers and isolated thunderstorms expected
from Sac terminals northward through tomorrow morning. Ceilings
will decrease to MVFR in heavier showers and again tonight into
Tuesday morning. Further south, VFR conditions expected to
prevail. Onshore flow expected with gusts up to 20 kts across the
Sacramento Valley thru this evening.

&&

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

&&

$$