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. && $$