Alta Sierra, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

985
FXUS66 KSTO 192026
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
126 PM PDT Sat Jul 19 2025

.DISCUSSION...

.SYNOPSIS...
Slight warmup through the weekend with continued dry conditions,
then high temperatures will cool back down to below normal through
at least the middle of next week. Breezy onshore flow will
continue into next week.

&&

.KEY MESSAGES...

*  Today and Tomorrow:

 - High temperatures return to seasonable levels today and
   tomorrow. Delta vicinity will have temperatures below normal
   thanks to enhanced onshore flow.
 - Smoke and haze from the Green Fire continues to linger around
   Redding, with KRDD reporting 6 miles of visibility and
   smoke/haze. Conditions have improved since this morning, at
   least in terms of visibility, however
 - Onshore flow and Delta Breeze influence expected through at
   least early next week, bringing minor cooling and overnight
   relief to the Delta and adjacent Valley.
- Breezy to gusty southerly winds expected this evening,
      especially in the vicinity of the Delta.

*  Next Week:

 - Upper level pattern: off-shore troughing continues. On Monday
   and Tuesday, trough will phase with a stronger low in Canada,
   lower heights across interior NorCal and introduce enhanced
   onshore flow. The Delta could see winds gusts approaching 40
   mph Monday afternoon through early Tuesday morning.
 - The Extreme Forecast Index (EFI, which essentially measures how
   anomalous a weather variable (max temperature, in this case)
   is based on model forecasts from the previous 20 years,
   highlights most of the Valley with high confidence for cool
   highs Tuesday through at least Friday.
- The Delta may struggle to break 80 on Tuesday
- Northern Sacramento Valley may struggle to hit 90 Tuesday
 - Periodically breezy onshore flow expected to persist in the
   afternoon and evening late this week, shifting toward terrain
   driven influence during the overnight hours in the Valley,
   foothills, and mountains.
 - Persistent and periodic late day wind gusts 20 to 30 mph
   anticipated throughout the Delta and vicinity each day.
 - Long term sneak peak: Temperatures are looking to climb back to
   near normal by the end of next week. Cluster Analysis reveals
   some uncertainty on what our upper-level pattern may look like.
   All four Clusters relatively agree off-shore troughing, with
   desert southwest ridge building, some disagreement on said
   strength of each synoptic feature. NBM following stronger ridge
   development, which will help to slightly weaken onshore flow,
   and allow temperatures to climb. Confidence increasing in
   return to July/summer like temperatures by the end of next
   week.

-Wood

.Changes from previous forecast...
 - Minimal changes from the previous forecast.

&&

.AVIATION...

VFR conditions expected next 24 hours across interior NorCal,
although periods of MVFR/IFR expected (highest chances 15z-20z) in
HZ/FU at RDD from ongoing Green Fire in Shasta County.
Periodically breezy west-southwest winds to continue as well, with
strongest gusts 20-25 kts through the Delta and vicinity after
22z, gradually decreasing after 06z.

&&

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

$$