322
FXUS66 KSTO 132009
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
109 PM PDT Sat Sep 13 2025

.DISCUSSION...

.SYNOPSIS...
Seasonable temperatures and drier weather this weekend except for
an isolated shower or thunderstorm over the Shasta County
mountains this evening into Sunday morning. Warming and drying
trend to above normal temperatures with periodically breezy
northerly winds early to mid week.

&&

.KEY MESSAGES...

* TODAY - SUNDAY:
 - Transient ridging aloft today, then a progressive shortwave
   trough looks to traverse the Pacific Northwest on Sunday

 - High temperatures in the 80s to around 90 expected at lower
   elevations, with 70s to low 80s at higher elevations

 - Slim (5-10%) chance for an isolated light shower/thunderstorm
   across Shasta County mountains this evening into Sunday morning as
   the shortwave moves through

* EARLY TO MID NEXT WEEK:
 - The shortwave trough shifts eastward early Monday, followed
   rapidly by amplifying ridging, allowing for drier and warmer
   weather early to mid next week

 - Increasing northerly winds expected Sunday night into Monday,
   strongest along and west of Interstate 5

   - Probability of Wind Gusts > 20 mph: 50-80% for the
     northern/central Sacramento Valley, Delta and adjacent Coast
     Range foothills

 - Lowering relative humidity, in the upper teens to upper 20s for
   the afternoon minimum RH.

 - Areas of Moderate HeatRisk Tuesday-Wednesday in the southern
   Sacramento Valley, Delta, northern San Joaquin Valley and
   adjacent foothills

 - Warming trend to above normal temperatures with Valley highs in
   the 90s

* LATE NEXT WEEK:

 - Potential for mountain showers and thunderstorms returning to
   the region late next week into next weekend although some
   uncertainty remains in the details

.CHANGES FROM PREVIOUS FORECAST...

&&

.AVIATION...
VFR conditions expected at interior NorCal TAF sites next 24
hours. Potential for MVFR conditions from slight chance of showers
near the Coastal Range but generally will be north and west of
Shasta County. Generally light winds less than 12 kts expected
outside of up to 15 kts in the afternoon across the Valley, and
then gusts 15-20 kts through Delta and adjacent Valley from 18z -
15z Sunday.


&&

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

&&

$$