135
FXUS66 KSTO 271831
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1131 AM PDT Mon Apr 27 2026


.KEY MESSAGES...

 - Mountain showers and isolated thunderstorms continue today into
   Tuesday, with some potential into the foothills and portions of
   the lower elevations of Shasta County this evening.

 - Dry weather and warming temperatures through Sunday.

 - Next system possibly late Sunday into early next week with low
   confidence at this time.

&&

.DISCUSSION...

...Today-Tuesday...
An upper trough extending from California northward to south
central canada slides across the area today and this evening. Not
much moisture or instability with this but enough that scattered
showers (30-50%) and isolated thunderstorms (10-20%) are expected
across most higher elevated locations. The valley should remain
try expect for a slight chance of portions of Shasta County.

Tuesday...the main upper trough slides off to the east but another
area of energy looks to drop into NorCal centered over western
central California by the end of the day. Looking at instability,
looks to be a big higher then today but will mainly in the Sierra
mostly areas south of I-80. CAPE values look to get up to around
300 j/kg which could be enough for a few showers to get to
moderate localized amounts of rain.

Upper level high pressure then looks to build into the area
Wednesday through Friday/Saturday. Temperatures look to rise
above normal with high temps in the mid 80s by Thursday and
Friday.

Ensemble are showing yet another possible upper trough to be
offshore of CA late Saturday into Sunday. Confidence a bit low at
this time so check back on how this system trends, but at this
time not looking like an impactful system at this time.

&&
.AVIATION...

VFR conditions at TAF sites next 24 hours. Light surface winds
generally 10 kts or less. Local MVFR conditions from scattered
mountain showers and isolated thunderstorms this afternoon and
evening until around 03z Tuesday. Additional mountain showers or
thunderstorms expected Tuesday afternoon and evening, with best
chances over the northern Sierra.


&&

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

$$