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A dry December so far for the Mother Lode


Water emerges at the base of Lyons Dam on Dec. 20. Lyons Reservoir was 62 percent full with 3,435 acre-feet as of Dec. 17. The historical average this time of year at Lyons is about 2,800 acre-feet. (Guy McCarthy / Union Democrat)
Fresh snow dusts edges of Lyons Reservoir on Dec. 20. The same fast-moving storm that brought the snow was the Mother Lode's last significant precipitation of a comparatively dry month so far. (Guy McCarthy / Union Democrat)
Lyons Reservoir was 62 percent full with 3,435 acre-feet as of Dec. 17, three days before this photo was taken. The historical average at Lyons this time of year is about 2,800 acre-feet. (Guy McCarthy / Union Democrat)
A sign at Lyons Dam shows the reservoir level is well below the maximum on Dec. 20. The manmade lake was 62 percent full with 3,435 acre-feet as of Dec. 17. (Guy McCarthy / Union Democrat)

The Mother Lode got two quick shots of rain and snow this month, but it’s been dry the rest of December, and the arid trend is expected to continue right up to New Year’s Eve.

Sonora has received 0.12 inch of rain, with a 0.03 inch on Dec. 3 and 0.09 inch a week ago today, Corey Mueller, a National Weather Service meteorologist in Sacramento, said Tuesday in a phone interview.

This week, residents of foothill towns in Calaveras and Tuolumne counties can expect sunny to mostly sunny skies through this weekend, with a slight chance of rain possible on

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The Mother Lode got two quick shots of rain and snow this month, but it’s been dry the rest of December, and the arid trend is expected to continue right up to New Year’s Eve.

Sonora has received 0.12 inch of rain, with a 0.03 inch on Dec. 3 and 0.09 inch a week ago today, Corey Mueller, a National Weather Service meteorologist in Sacramento, said Tuesday in a phone interview.

This week, residents of foothill towns in Calaveras and Tuolumne counties can expect sunny to mostly sunny skies through this weekend, with a slight chance of rain possible on New Year’s Day, which is Monday.

Since the current water year started Oct. 1, major watersheds in the Central Sierra, including the Stanislaus and the Tuolumne, have received 5 inches of precipitation. That’s 41 percent of average for the date Dec. 26.

It’s also more than 10 inches less precipitation than the same watersheds received through Dec. 26 last year, when the 2016-17 winter was the second-wettest on record.

And it’s about 4 inches less through the same date in the 2014-15 water year, one of the driest on record, however there’s still plenty of unused water in storage for now.

Reservoirs

Most major reservoirs in the Mother Lode were at least half full this week. Primary reservoirs holding water for more than 44,000 Tuolumne County residents were at least 60 percent full, greater than late December historical averages for the man-made lakes.

On the Mokelumne River, Pardee was 95 percent full with 194,167 acre-feet, and Camanche was 73 percent full with 302,800 acre-feet, according to state Department of Water Resources data.

On the Stanislaus River, Donnell Reservoir was 31 percent with 20,046 acre-feet, Beardsley was 47 percent full with 45,902 acre-feet, and New Melones was 83 percent full with 1,993,053 acre-feet.

On the Tuolumne River, Hetch Hetchy was 89 percent full with 322,820 acre-feet and Don Pedro was 81 percent full with 1,644,143 acre-feet.

On the South Fork Stanislaus River, water source for Tuolumne Utilities District and its customers, Pinecrest was 72 percent full with 13,264 acre-feet, Tom Haglund, general manager for TUD, said Tuesday. The historical average this time of year at Pinecrest is about 7,100 acre-feet.

Lyons was 62 percent full with 3,435 acre-feet, Haglund said. The historical average this time of year at Lyons is about 2,800 acre-feet. The most recent data for Pinecrest and Lyons was dated Dec. 17.

One acre-foot of water is enough to flood a typical American football field 12 inches deep.

La Niña

The first official day of winter in the northern hemisphere arrived Thursday last week.

Forecasters who watch the Pacific Ocean for signs of what to expect this winter say there’s a “weak La Niña signal” with “cooler than average equatorial water in the central Pacific,” said Michelle Mead, a warning coordination meteorologist in Sacramento.

What that means for the Mother Lode and the rest of the Central Sierra is hard to tell, because past La Niñas have resulted in a range of different outcomes, Mead said.

Of the 10 La Niñas in the past 65 years, one of those produced a wet winter in the Golden State, three resulted in normal winters and six produced dry winters.

No two La Niña seasons are the same, Mead said.

Drought monitor scientists say more than 44 percent of the Golden State is abnormally dry this week, and 12.69 percent is in a stage of moderate drought.

All abnormally dry and drought areas in California are south of Tuolumne County.

So Cal

As of Tuesday, there were still five personnel from Cal Fire’s Tuolumne-Calaveras Unit assigned to the Thomas Fire in Ventura and Santa Barbara counties, said Greg Adams, a division chief based in San Andreas.

Since Dec. 4, the Thomas Fire has burned more than 440 square miles, destroyed 1,063 buildings, damaged 280 structures, and killed one firefighter and one civilian.

The Thomas Fire was estimated to be 88 percent contained as of Tuesday morning. There was little to no active fire and very little smoke, according to Cal Fire. The fire was not expected to make any more forward progress, but 899 total personnel remained assigned to the massive burn area.

The cause of the Thomas Fire was said to be under investigation. Cal Fire and the Forest Service say it’s now the largest wildfire in modern California history.

Contact Guy McCarthy at gmccarthy@uniondemocrat.com or (209) 588-4585. Follow him on Twitter @GuyMcCarthy.