Forecasters say snow, rain on way to Sierra

A winter storm is forecast to arrive in the Central Sierra on Tuesday, bringing much-needed rain and snow to the parched region.

The National Weather Service says a slight chance of precipitation tonight will develop into a 70 percent chance Tuesday. Clear skies are again forecast for Wednesday and the next chance of precipitation comes Sunday.

The 2011-12 rain season — which began July 1 and ends June 30 — has been unusually dry.

 Sonora has gotten only 8.07 inches of precipitation this year. Average for this time of year is about 32 inches.

Two weeks ago, a storm passing through the area dropped about four inches of rain and eight inches of snow in the higher elevations. Before that storm, 33 days passed without precipitation, according to the National Weather Service.

Dry spells of more than 30 days are rare in this area. The most recent was in 2008, from the end of February through late March, but the last time there was no rain for 33 days or more during the winter was in 2000, from Dec. 10 to about Jan. 10, said National Weather Service meteorologist Jim Mathews, in Sacramento.

The longest winter period without precipitation was 44 days in 1976, he said.

Temperatures — hovering in the low to mid-50s during the day — are on par with historic averages.
The lack of rain and snow can be chalked up to a high-pressure system over the eastern Pacific and West Coast that is keeping storms out of our area, Mathews said.

The atmosphere is filled with low-pressure troughs and high-pressure ridges.

While there’s usually a ridge over the Pacific and Gulf of Alaska, it’s stronger this year and is preventing low pressure systems from coming down from Alaska, Mathews explained.

"It's stronger this year than last year. That’s why it’s been drier in our area,” Mathews said.
“Unlike last year, low pressure (systems) from Alaska dipped into our area and gave us cold storms accompanied by snow and rain,” he said.

“Sometime, before the end of time, it will rain in Tuolumne County,” Mathews joked.