A wet weather system billed as a powerful, high-impact storm is approaching the Mother Lode and the rest of the Central Sierra with potential for heavy rains, heavy snow and thunderstorms starting Friday night and lasting into Sunday.
“This storm origin is the north Pacific south of the Aleutian Islands,” Brendon Rubin-Oster, a National Weather Service meteorologist in Sacramento, said Friday in a phone interview. “It’s strengthening and interacting with a subtropical plume of moisture from near the Hawaiian Islands chain and setting up an atmospheric river event.”
What that means in Calaveras and Tuolumne counties is rains are expected to begin a couple hours after dark Friday, between 8 p.m. and 10 p.m. The sunny weather evident Friday during the day is not expected to return until Monday.
This is not a freezing storm system bringing ice and snow to Mother Lode foothill towns. Overnight lows in Sonora and other communities along Highway 49 are expected in the 40s Friday night and Saturday night, with cooler temperatures moving in Sunday evening as the storm system exits. Overnight lows Sunday night could dip into the mid-30s.
Sonora residents can expect 2 to 3 inches of rain Friday to Sunday. Three feet to 4 feet of snow are expected at Ebbetts Pass and Sonora Pass. Two feet to 30 inches of snow are expected at Tioga Pass.
Snow levels with this approaching storm are expected to begin around 6,500 feet elevations, east of Arnold, east of Calaveras Big Trees, east of Strawberry, east of Pinecrest, and east of Groveland and Pine Mountain Lake. Snow levels are expected to drop to 5,500 feet levels Saturday night and into Sunday morning. Pinecrest is at 5,680 feet elevation. Strawberry is around 5,325 feet.
All the Mother Lode passes on Highway 4, Highway 108, and Highway 120 -- Ebbetts Pass, Sonora Pass, and Tioga Pass -- are closed for the winter season.
Anybody heading down to the Central Valley between Friday night and Saturday can expect gusting winds up to 40 miles per hour. In the Sonora area, winds are expected 15 mph to 20 mph through Saturday evening.
Forecasters say their confidence is high for heavy snow, medium for winds strength and medium for the chance of thunderstorms Saturday and Sunday.
Contact Guy McCarthy at email@example.com or 588-4585. Follow him on Twitter at @GuyMcCarthy.