Castella, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

479
FXUS66 KSTO 251915
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1215 PM PDT Mon May 25 2026

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

.KEY MESSAGES...

 - Gusty southwesterly winds today combined with low daytime RHs,
   will lead to Elevated Fire Weather conditions in the Valley.

 - Chances for isolated showers/thunderstorms Tuesday-Thursday
   afternoon and evening over the Sierra and Shasta County.

&&

.DISCUSSION...

...Today through Tuesday...

Current conditions across the area show higher level clouds in the
northern portions of the forecast area around Redding with
temperatures in the 70s. Winds have started to slowly increase
across the Valley, with gusts of 20-25mph being reported near the
Delta. We will continue to see the winds increase throughout the
day, with gusts of 30-40mph possible within the Valley and Delta.
RH values will drop this afternoon when we get temperatures into
the 80s for daytime highs. The low RH values combined with the
breezy south to southwesterly winds bring elevated fire weather
concerns to the Valley today. The highest chances lie in the
northern Sacramento Valley where temperatures are warmer, winds
are higher, and RH values are lower. Please do be mindful of any
outdoor activities that involve fire/flame; the fuels will only
continue to dry as we dive into the dry season.

Temperatures will slowly cool off on Tuesday, with highs in the
70s with filtered sunshine. Latest HIRES and NBM guidance has RH
values improving tomorrow along with winds diminishing. This has
been the case over the past several runs of the NBM. Thus, we
decided to remove the Elevated Fire Weather concerns for Tuesday
as forecasted conditions have improved. We will continue to
monitor conditions across the area for any fire weather concerns
Tuesday.

A low pressure system will track through the region on Tuesday
bringing moisture to the higher elevation and potentially down
into the foothills. Isolated shower and thunderstorm activity has
been picked up in the NBM and HIRES guidance for Tuesday afternoon
and evening. The highest chances lie around Shasta County and in
the Sierra. Snow levels will be at 7000 feet, but will slowly
drop toward 6000-7000 feet late Tuesday and into Wednesday. Areas
south of Highway 50 in the Sierra at the higher elevations have
the best chances to see snow. Accumulations are expected to be
minor.

...Wednesday and onward...

The low pressure system continues to move through the region
Wednesday and Thursday, with winds increasing out of the north.
Wind gusts of 25-35mph are possible on Wednesday, with the highest
winds along and west of I-5 in the Sacramento Valley. The trend
for the past couple of runs of the NBM have had RH Values
increasing and winds being lighter across the region. This has
allowed us to drop the Elevated Fire Weather concern headline for
Wednesday. However, we will continue to monitor conditions and the
latest HIRES guidance to see if any headlines are needed to be
re-added for fire weather concerns on Wednesday.

Shower and isolated thunderstorms are possible in the mountains
and foothills Wednesday and Thursday. A few of the storms could be
on the stronger wide, with small hail and gusty winds possible.
There is a slight chance (less than 20 percent) for an isolated
shower within the Valley Wednesday/Thursday. Chances for light
snow at the highest elevations south of Highway 50 in the Sierra,
with snow levels above 7000 feet Wednesday afternoon. Post
Thursday, we will start to see temperatures increase slowly as the
low pressure system exists the region.

&&

.AVIATION...

VFR conditions are expected through the TAF period, with breezy
south to southwesterly winds. Gusts of 25-35kts will be possible
for the Sacramento sites, RDD, and RBL. Winds will be out of the
north to northwest for SCK and MOD today, with a few gusts to
20kts. SCT to BKN clouds move through the region later this
evening and overnight. Otherwise, winds go light and variable
overnight and into tomorrow morning.

&&

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

&&

$$