Rain on snow

Whitewater on Sullivan Creek under Mono Way before noon on Friday in Sonora.

A slow drive from East Sonora up Tuolumne Road to Highway 108 told most of the story Friday.

Warm rains were swelling new creeks and streams at every low spot, melting slopes, drifts and berms of snow, and unleashing mudslides and snow slides, while workers in fluorescent vests and helmets dug out drainage ditches and drove excavators to try to relieve intense flooding conditions from the township of Tuolumne to Twain Harte.

Whether predictions for up to 100 inches of new snow on Ebbetts, Sonora, and Tioga passes this weekend prove true or not, most people at lower elevations in the Mother Lode know they can expect mostly rain with the current storm through Sunday, and then again Monday through Wednesday.

“Today through Sunday and then another similar storm Monday through Wednesday, both of these are atmospheric river storms,” Cory Mueller, a National Weather Service meteorologist in Sacramento, said Friday afternoon in a phone interview. “They are definitely tapping into that deeper subtropical moisture. That’s why the snow levels are so much higher with these storms, they’re pulling in warmer air and more moisture.”

With some mountain residents already dealing with 4 to 5 feet of snow on their roofs, Tuolumne County Office of Emergency Services staff were already aware of at least 10 roof collapses earlier this week, including a roof collapse at at least one business. Friday morning, they became aware of at least a couple more roof collapses and a half-dozen homes already flooded.

County officials also announced Friday afternoon that the Community Resilience Center at 18241 Bay Ave. in Tuolumne is now open as an evacuation center for anyone who has had to leave their homes due to collapsed roofs, flooding, or other unforeseen circumstances. 

Sand and sandbags were also available again Friday at locations in Columbia, Tuolumne, Jamestown and Big Oak Flat.

The severity of storm impacts already being felt up and down the Golden State, along with dire forecasts for more warm rain-on-snow flooding this weekend and next week, prompted a federal emergency declaration Friday for Tuolumne and 33 other counties, signed off by President Joe Biden. 

State and federal declarations that include Tuolumne County could free up future disaster assistance funding for local government agencies and individual property owners and tenants.

Sonora received record-breaking rainfall on Thursday, with 1.9 inches, breaking the previous record for March 9, 1.72 inches set back in 1939.

As of 2:30 p.m. Friday, with sheets and intermittent deluges of rain coming down, Pacific Gas and Electric Co. crews were responding to scattered outages in Sonora, East Sonora, Cedar ridge, and Twain Harte, and the utility giant was warning Mother Lode customers to expect more weather-related outages.

Weather-related traffic incidents Friday afternoon in Tuolumne County included a hit-and-run vehicle striking a building, reportedly Serendipity Gifts and Antiques, on Main Street and Highway 120 in downtown Groveland at 2:31 p.m.; and another incident involving a male walking Middle Camp Road or Longeway Road with a cone on his head, insisting a traffic incident was not a collision. Both incidents were reported by California

Highway Patrol communications staff. 

Farther east up Highway 120 and the Tuolumne River watershed, authorities in Yosemite National Park were advising they expect to keep the park closed through at least next Thursday to clear snow from man-made roads, other infrastructure, and buildings. Man-made properties in Yosemite are the only things at risk in the park. Nature is thriving.

Tuolumne Utilities District staff warned residents and customers of rain-on-snow flooding concerns Friday, and TUD workers have already tried to “turn off” water in the agency’s ditches. That’s easier said than done on the miles of open ditches that date to the Gold Rush. Shaws Flat Ditch at Lyons Bald Mountain Road was full of runoff from one of the road’s drainage ditches, and more runoff from other new creeks and streams further downstream.

“While TUD crews are doing everything possible to utilize its spills to relieve the ditches

of snowmelt and stormwater, the ditches are likely to become overwhelmed and in some areas the stormwater may spill over the ditch berms,” Emily Long with TUD communications said. 

“Property owners living below any creeks, streams, rivers, and ditches should be prepared. TUD’s water and wastewater systems continue to be taxed by numerous consecutive storms, power outages, and road closures which may result in delayed response times. We apologize for any inconvenience this may cause as we work to triage issues as they arise.”

As of Friday, a five-station index including Calaveras Big Trees and Hetch Hetchy showed principal watersheds of Calaveras and Tuolumne counties had received 46.7 inches of precipitation since the current water year began Oct. 1 — 162% of average for the date March 10.

Forecasters said the Sonora area could get 3 to 4 more inches of rain Friday to Sunday, and 4 to 5 more inches of rain Monday to Wednesday.

Also Friday, 49 snowpack sensors across the Central Sierra showed average snow-water equivalence of 52.1 inches, 206% of normal for the date March 10.

The current storm could bring 60 to 80 inches more snow to Ebbetts, Sonora, and Tioga passes by Sunday, and 4 to 5 more feet Monday to Wednesday.

Calaveras, Tuolumne and Mariposa counties were declared drought-free last week for the first time in three years.

Record-setting atmospheric river storms in late December and the first half of January, along with more recent colder storms packing low-elevation snow, sleet, and icy rains, have combined to reduce drought intensity in Calaveras and Tuolumne counties to “none,” according to U.S. Drought Monitor scientists.

For the most up-to-date information on sand and sandbag locations, evacuation centers and shelters, go to www.tuolumnecounty.ca.gov/1524/Office-of-Emergency-Services.

Contact Guy McCarthy at gmccarthy@uniondemocrat.net or (209) 770-0405. Follow him on Twitter at @GuyMcCarthy.