079 FXUS66 KSTO 102022 AFDSTOArea Forecast Discussion National Weather Service Sacramento CA 122 PM PDT Fri Oct 10 2025
For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing.
.SYNOPSIS... A weak system continues bringing scattered showers and thunderstorms this afternoon and evening north of I-80. A colder, wet system will then bring widespread rainfall and the season`s first measurable snowfall to the mountains, though exact amounts and timing are still uncertain.
.KEY MESSAGES...
* TODAY - SUNDAY:
- A weak system continues to bring breezy winds and scattered showers today, with precip primarily in Shasta County and the southern Cascades. Potential for rain continues through Saturday afternoon with a 55 to 80% chance of 0.25 inches in the aforementioned areas through Saturday.
- 10-20% chance for thunderstorms this afternoon/evening in Shasta County.
- Briefly drier conditions on Sunday before the next system arrives early next week.
* MONDAY - WEDNESDAY:
- A colder, wet system arrives early next week, bringing widespread rainfall and the season`s first measurable mountain snowfall through Wednesday evening.
- Exact timing and amounts are still uncertain for this system, but a Winter Storm Watch has been issued from Monday morning to Wednesday evening for the Sierra south of I-80 and above 6500 ft. Biggest impacts are expected south of HWY 50.
- 10-20% chance of thunderstorms Monday evening into Tuesday morning as well, as the system begins to move onshore.
.AVIATION... A weak system will bring isolated MVFR conditions due to scattered showers north of I-80 and a 10-20% chance of isolated thunderstorms over Shasta County and adjacent terrain between 21Z Friday and 02Z Saturday. South winds 10-15 kts with gusts 15 to 20 kts through the Delta and northern/central Sacramento Valley until 04Z Saturday. Southwest gusts up to 20-30 kts over the mountains through 23Z Saturday.
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.STO WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Monday morning through Wednesday evening for West Slope Northern Sierra Nevada.
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NWS STO Office Area Forecast Discussion