Alta, CA Weather

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

Key messages

- Cool and mostly dry weather through Friday

- Pattern change to unsettled weather Saturday into Sunday, with rain and mountain snow above 6000-7000 feet

- High pressure will promote a drying and modest warming for Sunday and Monday

- Breezy north to east winds Sunday into Monday

Discussion

: Today through Friday:

Cool and mostly dry weather pattern with light winds is expected to persist across northern interior California through Friday. Although, a weak surface high pressure is promoting a modest warming today. Afternoon highs in the mid 60s into low 70s for the Valleys, 55-65 in the Foothills and 50s-60s in the mountains today. Cold morning lows are expected for the mountains and higher elevation basins the next few days, with near to below freezing temperatures. Patchy fog or haze will be possible each morning in the Valley.

A larger upper-level trough is expected to deepen offshore Thursday and Friday, with a series of embedded weak shortwave moving across the area. This will bring a slight chance of isolated mountain showers over the Sierra. Elsewhere, will see mostly increasing mid to high clouds.

: Saturday through Tuesday:

A system will moves across the area Saturday into Sunday bringing an increasing chance of rain and mountain snow above 6000-7000 feet. Uncertainties remain on how much moisture will arrives across the area, as well on the exact amounts. There is a near 50% chances of measurable rain (0.01") for the Valley, with higher chances across the eastern portions of the forecast area. The chance for wetting rain (0.10") is 20-45% for the Valley, with the highest chances in Stockton and Modesto counties. While the models tend to agree that the higher rain chances will occur over the Sierra Foothills and mountains. The 25th percentiles shows 0.1-0.4 inches over the Sierra mountains Saturday into Sunday, the 75th percentile range 0.75-1 inch and the 90th percentile showing 1.5-2 inches. The Sierra foothills have a 90th percentile of 0.8-1.5 inches of rain throughout Sunday. As for the Valleys, 90th percentiles between 0.1 to 0.5 inches for the Sacramento Valley and 0.7 to 1 inch for the northern San Joaquin Valley.

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. There is a 35 to 60% chances of snowfall exceeding 3 inches for the higher terrain over the Sierra Saturday into Sunday, especially south of the US-50.

Ensemble cluster shows a ridge building in right after the trough exits 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.

Aviation

VFR conditions prevail across interior NorCal next 24 hours. Surface wind gusts generally below 12 kts. Low probabilities of BR developing around 10z Thursday at the northern San Joaquin Valley TAF sites.

Watches, warnings and advisories

None.