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Wx Forecast - Wx Discussion - Wx Aviation

062
FXUS66 KSTO 252011
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
111 PM PDT Fri Jul 25 2025

.DISCUSSION...

.SYNOPSIS...
Near to below-normal temperatures expected into next week breezy
onshore winds at times. Chances for afternoon and evening
mountain thunderstorms today through the weekend.

&&

.KEY MESSAGES...

*  Today:
 - Afternoon highs in the 80s and low 90s throughout the Valley as
   below normal highs continue.
 - Onshore winds will be gusty through the Delta and into the
   Valley late afternoon and evening.

 Thunderstorms:
 - Chances (25-45%) for isolated to scattered mountain showers and
   thunderstorms this afternoon and evening as upper low moves
   overhead. Main storm hazards include lightning, brief heavy
   rain, gusty winds, small hail, and possible fire starts.
 - There is a 15-30% chance of isolated thunderstorms in the
   northern Sacramento Valley late this afternoon into the early
   evening hours.
 - A stray shower or storm may develop over the Sierra during the
   overnight hours tonight into early Saturday morning in the
   vicinity of Interstate 80 and Highway 50.
 - Elevated fire weather conditions are expected in the mountains into
   the weekend due to the lightning threat and any strikes
   outside the main precipitation core will pose the threat for
   fire starts.

* Saturday-Sunday:
 - Chances (15-30%) for isolated to scattered mountain showers
   and thunderstorms continue on Saturday with the highest
   potential over the Sierra crest.
 - Storms are expected to form along the crest and move
   northeastward, resulting in most of the activity occurring
   outside of interior Northern California.
 - Thunderstorm chances decrease on Sunday over the Sierra to
   10-20%.

* Long Term:
 - Slight warming trend early next week, but highs will remain
   below normal.
 - Periodically breezy onshore flow expected during the
   afternoons and evenings next week.

.Changes from previous forecast...
 - Potential for mountain thunderstorms by the middle of next week
   during the afternoon and evening hours.

&&

.AVIATION...
Mostly VFR conditions expected over the next 24 hours across
Interior NorCal. Isolated to scattered mountain thunderstorms may
cause MVFR/IFR conditions until around 03z-06z Saturday. Isolated
thunderstorms possible over the Sierra crest after 18z Saturday.
For the Valley, south to southwest surface winds generally less
than 12 kts with gusts up to 15 to 20 kts through 06z Saturday and
again after 21z Saturday. For the Delta vicinity, sustained winds
10 to 20 kts with gusts 20 to 30 kts at times. Non-zero chance
(less than 10%) for MVFR ceilings from 12Z to 16Z Friday in the
Delta and adjacent Valley locations.

&&

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

$$