Ono, CA 96047 Weather

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

Key messages

- Light rain and mountain snow showers continue today for the Sierra and surrounding areas, accompanied by a low chance of isolated thunderstorms this afternoon into early evening

- Cooler temperatures, rain and mountain snow above 7,000 feet Saturday into Sunday

- Winter Weather Advisory in effect from 8 AM Saturday to 7 AM Sunday for elevations above 7000 feet in the Sierra Nevada

- Drier and warmer conditions Sunday through early next week, but temperatures will remain below-normal for this time of year

Discussion

A slow moving weak cold front is traversing Northern California today. As of 11AM, isolated light rain and mountain snow showers continues over portions of the Sierra. Shower activity will continue this afternoon with mix rain and snow over the Sierra, with spotty rain showers in the vicinity. There is a low chance of isolated thunderstorms, capable of and brief heavy downpours this afternoon into early evening. Generally dry weather is expected for much of the forecast area through today.

Increasing chances of precipitation is expected tonight and Saturday as a broad and deep upper low centered in the Northeastern Pacific and a low in the Eastern Pacific interact and shift eastward across the region through Sunday. Precipitations amounts have been trending slightly higher over the Sierra with this system, especially south of I-80 where up to 2.5 inches of rain is expected. The 00Z ECMWF Extreme Forecast Index highlight 50-70th percentile above normal QPF for portions of the Sierra south of I-80. Most likely rain total amounts range 0.5 to 2.5 inches over the mountains and 0.2 to 1 inch for foothills, with the highest amounts in the Sierra foothills. Meanwhile, lighter amounts ranging from a trace to 0.2 of an inch are expected for the Valleys and Coast Range, with the highest amounts in Shasta and eastern Modesto counties. Colder air aloft will bring an increasing instability on Saturday, capable of produce brief heavy downpours and a chance of isolated thunderstorms. Snow levels are expected to be above 7000 feet on Saturday, lowering to 6000-7000 feet Saturday night into Sunday. The snowfall total amounts are also trending higher with this system over portions of the Sierra Nevada, with the heaviest snowfall amounts expected above 7000 feet. Total snow accumulations up to 10 inches, with up to 25 inches at the highest peaks. Minor accumulations of up to 3 inches possible down to 6000 feet. Some light flurry will be possible as low as 5000 feet, but no snow accumulation are expected below 6,000 feet. A Winter Weather Advisory is now in effect from 8 AM Saturday to 7 AM Sunday for Northern Sierra above 7000 feet, including Highway 50 and Interstate 80.

High pressure build in in the wake of the trough on Sunday. Resulting in drying and modest warming Sunday through early next week. Breezy to east northerly winds are expected to developed across the area, with the strongest winds over the Sierra. Clusters are showing another upper-level trough approaching the area Tuesday, but there is a lot of uncertainty in the timing and position of this system.

Aviation

VFR conditions prevail across interior NorCal next 24 hours. Surface wind gusts generally below 12 knots across Valley TAF sites through 20z Saturday, when occasional gusts up to 20 kts can be expected in teh northern Sacramento Valley, adjacent foothills, and in the mountains. Low to mid-level clouds will continue through Saturday, slightly lowering ceilings at TAF sites. Light Valley rain showers possible, with chances increasing late Saturday.

Watches, warnings and advisories

Winter Weather Advisory from 8 AM Saturday to 7 AM PDT Sunday for Sierra (Cal-Tuo) Above 5000 ft-Sierra (El Dorado-Amador) Above 5000 ft-Sierra (Sierra-Placer) Above 5000 ft.