599
FXUS66 KSTO 271915
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1215 PM PDT Wed Aug 27 2025

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

.DISCUSSION...

.SYNOPSIS...
Isolated mountain showers and thunderstorms today, mainly along
the Sierra/Southern Cascades crest. Elevated fire weather
conditions in the mountains from lightning and gusty erratic
outflow winds. Seasonable high temperatures, along with drying
conditions today through the weekend.

&&

.KEY MESSAGES...

* Today:
 - 15-35% chance of isolated mountain thunderstorms today in the
   Sierra and southern Cascades. Best chances along and east of
   the crest, as stronger monsoonal moisture advection will occur
   east due to Four Corner`s ridge breaking down.
   -- Any thunderstorm that develops will mainly be wet, however
      lightning strikes outside of the precipitation core pose a
      risk for new fire starts. Gusty, erratic outflow winds are
      also a concern.
 - High temperatures will be seasonable, with mostly low to mid
   90s in the Valley; cooler mid to upper 80s in the Delta. Minor
   HeatRisk across interior NorCal.

* Thursday - Weekend:
 - PacNW low builds off coast; enhanced onshore flow will usher
   in a slight (5%) chance of a shower/t-storm on Thursday in
   southeast corner of Tuolumne County, dry conditions elsewhere
 - Seasonable temperatures with Minor to locally Moderate
   HeatRisk
 - High temperatures mainly in the 90s across the Valley and Delta
 - Minor drying brings lower relative humidity over the weekend
   especially to the northern Sacramento Valley where daytime RHs
   in the mid teens are forecast

.Changes from previous forecast...
- No significant changes from previous forecast

&&

.AVIATION...

Isolated thunderstorms are expected this afternoon
and evening within the Sierra Range and southern Cascades, with
TAF locations remaining dry. SCT clouds this afternoon and evening
near RDD and MOD while SKC prevails through the remainder of the
sites. 10-15kt winds this afternoon, with light and variable
overnight for each TAF locations. VFR conditions are expected
through the TAF period.

&&

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

$$