135
FXUS66 KSTO 181938
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1238 PM PDT Fri Jul 18 2025

.DISCUSSION...

.SYNOPSIS...
Continued dry and seasonable conditions through the end of the
work week. Slight warmup over the weekend, 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:

 - High temperatures continue to be slightly below normal, with
   highs running around 1 to 4 degrees below what is expected for
   this time of year.
 - Current GOES-18 Visible shows a layer of haze/smoke lingering
   in the Redding area. ASOS observations at Red Bluff AP show
   southerly winds developing. Southerly winds forecast to develop
   in the next 1-3 hours should help disperse smoke and haze.
 - 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.

*  Weekend - Middle of Next Week:

 - Upper level pattern remains largely persistent with broad
   troughing/northwesterly flow across interior NorCal.
 - Near seasonable temperatures continue, increasing slightly over
   the weekend, before cooling again early next week. The cooldown
   next week could see temperatures 10 to 15 degrees below July
   normals for interior NorCal.
 - 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 this weekend and next week, shifting
   toward terrain driven influence during the overnight hours.
 - 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.

-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 12z-21z) 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.
&&

$$