790
FXUS66 KSTO 311957
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1257 PM PDT Thu Jul 31 2025

.DISCUSSION...

.SYNOPSIS...
Chances for afternoon and evening thunderstorms continue through
this evening over the mountains mainly in the Shasta County area.
Near to slightly below normal temperatures are expected this week
as periodically breezy onshore winds continue.

&&

.KEY MESSAGES...

* Today:
 - Thunderstorm chances around 10-25% across Shasta County
   mountains for this afternoon/evening. Models show storms
   forming along the Coastal Range then moving north/northeast
   through the afternoon/evening.
 - Main storm hazards include lightning, brief heavy rain, gusty
   winds, small hail, and possible fire starts. Simulated
   reflectivity shows best chances for thunderstorms will be 4-9
   PM.
 - Elevated fire weather conditions are expected in the mountains
   into the due to the lightning threat and any strikes outside
   the main precipitation cores will pose the threat for fire
   starts.
 - Afternoon highs in the 90s throughout the Valley as high
   temperatures approach normal leading into next week
 - Periodically breezy onshore flow expected during the afternoons
   and evenings.

* Friday - Weekend:
 - Isolated mountain thunderstorm chances 10-20% on Friday and
   less than 10% on Saturday along and near the Shasta County
   mtns.
 - Periodically breezy onshore flow persists, with a slight uptick
   in wind speed possible by Sunday.
 - Probability of south to west wind gusts across the Delta and
   nearby area > 30 mph on Sunday:60-90%
 - Near to slightly below normal temperatures expected to
   continue.

.Changes from previous forecast...
 - No significant changes in the forecast this period.
 &&

.AVIATION...

Generally VFR conditions expected to prevail next 24 hours across
interior NorCal. MVFR/IFR possible in isolated mountain
showers/thunderstorms across Shasta County terrain through Fri
06z. Otherwise, breezy onshore surface winds up to 12 kts expected
through Valley and Delta, with lighter terrain driven winds at
higher elevations. Gusts 20-25 kts in Delta and vicinity from
21-12z Friday, decreasing through the early morning.

&&

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

$$