Environment

More lightning and rain, possibly tornadoes in storm’s second wave

The atmospheric river is making its presence felt in Sacramento area as rain falls on the campus of UC Davis in Davis on Friday.
The atmospheric river is making its presence felt in Sacramento area as rain falls on the campus of UC Davis in Davis on Friday. mcrisostomo@sacbee.com

A second blast of weather expected Sunday could be even more intense than the first, according to the National Weather Service, which warns that the Sacramento Valley could see hail, additional lightning and even a possibility of tornadoes.

All this could result from thunderstorms defined as “severe,” said meteorologist Holly Osborne, meaning winds of 58 mph or more and hail as big as 1 inch or larger.

This next wave of weather is expected to begin before dawn Sunday and last into evening. Overall, the storm could be more eventful than Friday’s blast.

“It does look unstable,” Osborne said. “Rainfall amounts might be a little less, but we’re expecting maybe more thunderstorms. If you happen to be under a thunderstorm, you’re going to get a downpour. But in general, rainfall amounts will be less.”

The heaviest rainfall from Friday’s storm, as predicted, hit after dark. In some areas, Sacramentans woke up Saturday to flooded intersections and clean blue skies poking through moody clouds.

For the 24 hours ending at 9 a.m. Saturday, downtown Sacramento received 1.14 inches of rain. Sacramento International Airport received 1.49 inches, while Executive Airport received 1.39 inches, breaking a record for the date. Greater amounts were recorded in most Sierra Nevada foothill locations.

Lightning and strong winds caused most of the power outages in Friday’s storm. Thousands of Pacific Gas and Electric Co. customers throughout the Sierra Nevada foothills were still without power Saturday evening. The biggest of these is in Plumas County, where about 10,000 customers were without power.

PG&E spokesman J.D. Guidi said he expected power to be restored in Nevada, Placer and El Dorado counties at some point Saturday night. But he had no estimate for restoring power in Plumas and Shasta counties.

Most of these outages were likely caused by strong winds that toppled trees or power lines. Many of the outage locations cannot be reached easily because of fallen trees, Guidi said.

“We still have some access issues up there,” Guidi said. “We are working as safely and quickly as possible.”

PG&E planned to bring in additional crews from Oregon and Washington to help resolve these outages, and to prepare for more trouble Sunday.

Sunday’s storm is expected to hit before dawn – earlier than previously predicted – and likely will bring a return of strong winds along with increased thunderstorm activity. The Sacramento metro area could see peak winds of 45 mph, with 60 mph or greater possible in the mountains.

The likelihood of tornadoes Sunday is considered “marginal,” according to the National Weather Service, but the unstable weather means they could form throughout the Sacramento Valley as well as the northern San Joaquin Valley. Tornadoes are not common in the area, nor are they as large as those that strike the Midwest states. But they do occur and have been strong enough to uproot trees and damage buildings.

Sunday’s storm will be colder, dropping snow levels in the Sierra to 5,000 feet by early Monday. It will also shift farther south, boosting rainfall totals in the northern San Joaquin Valley. Stockton and Modesto could see three-fourths of an inch of rain, compared with just a couple tenths received in Friday’s storm.

Elevations above 8,000 feet could see more than a foot of new snow. Areas at the highway passes will likely see 6 inches or less.

Sacramento may see an additional inch of rain by Monday morning, with 2 to 3 inches possible in the foothills, Osborne said. But the storm is expected to ease off in Sacramento in time for the Monday morning commute.

“The widespread rain will probably decrease Monday morning, but then we might get some more thunderstorms and showers for Monday afternoon,” she said.

No serious flooding is predicted on the Sacramento River. But the Sutter and Colusa bypasses alongside the river are expected to begin flooding Sunday morning – as designed – to take pressure off the main river channel. This is mostly caused by heavy runoff from small creeks below the dams.

Major dams around the region are expected to capture virtually all the runoff from this weekend’s storms, because they have plenty of storage available after three years of drought.

Alan Haynes, service coordination hydrologist at the California-Nevada River Forecast Center, said the large reservoirs are predicted to gain more than 1 million acre-feet of new water supply from the weekend storms.

For example, the water level in Oroville Reservoir, the second-largest in the state, rose nearly a foot as runoff from upstream nearly doubled in volume from Friday’s storm.

“We’ll see what this one does, but it looks like things have behaved, for the most part, in a beneficial way,” Haynes said.

Call The Bee’s Matt Weiser at (916) 321-1264. Follow him on Twitter @matt_weiser. Staff writer Jim Miller contributed to this report.

RAINFALL TOTALS

Selected storm totals from Sacramento and the region for the 24 hours ending at 9 a.m. Saturday:

Downtown: 1.14”

Executive Airport: 1.39”

International Airport: 1.49”

Vacaville: 1.65”

Davis: 1.91”

Grass Valley: 2.67”

Auburn: 1.79”

Marysville: 1.27”

Kingvale: 3.61”

Kyburz: 2.38”

Pacific House: 2.54”

Stockton: 0.50”

Modesto: 0.18”

Source: National Weather Service

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