SAN FRANCISCO (CBS SF) — A potent winter cold front ripped through the San Francisco Bay Area Thursday’s morning, triggering treacherous driving conditions and flooding roadways, officials said.

Intense storm cells began to descend over San Francisco shortly after 8 a.m. and would continued to produce potent short-lived downpours until around 10 a.m.

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Over the past 24 hours as of 5 p.m., 1.46 inches of rain had fallen in Mill Valley, 1.12 inches in San Francisco and 2.04 inches in the Santa Cruz Mountain community of Ben Lomond.

Rain wasn’t all that fell in those mountains to the south.

Hail fell for about 15 minutes at the higher elevations around 2,000 feet. The cold temperatures allowed the tiny balls of ice to pile up, looking like snow.

“You don’t see hail too often up here. People might want to stop and take pictures. We recommend don’t stop on the side of a highway for any of that,” said CHP Officer Adam Rikalo. “It’s a fantastic sight to see. Tell the story when you get home.”

On Mount Umunhum, an SUV lost control and went off the road after two inches of hail accumulated, making for slick conditions.

Several roadways in Marin, Alameda and Contra Costa counties were flooded.

Raw video of flooded Oakland road


“It means a burst of moderate to heavy rain is possible with the front,” the National Weather Service said of the brunt of the storm. “Impacts could be brief ponding on roadways, minor urban flooding, and hazardous conditions for motorists.”

The weather service issued a small stream and urban flood advisory for parts of Alameda and Contra Costa counties until 11 a.m.

“Some locations that will experience minor flooding include Oakland, Concord, Antioch, San Leandro, San Ramon, Walnut Creek, Pittsburg, Danville, Martinez, Pleasant Hill, Lafayette, Castro Valley, Hercules, Pinole, Orinda, Moraga, Clayton, West Pittsburg, Blackhawk-Camino Tassajara and Blackhawk,” forecasters warned.

High, gusty winds also pounded the Bay Area. Gusts were whipping up to 35-50 mph with the strongest being clocked on Mt. Diablo in the East Bay.

The storm front struck the North Bay first and continued its march southward. Forecasters said rainfall totals would generally be 1-3 inches in the North Bay and coastal mountains. Elsewhere, total will range from quarter of an inch to an inch.

The storm was also creating havoc at San Francisco International Airport. There were at least 33 flights canceled into and out of the airport. SFO spokesman Doug Yakel said the cancellations were evenly split between arrivals and departures, mostly shorter flights along the West Coast.

By Thursday afternoon, forecasters said, a layer of unstable cold air will be perched over the Bay Area, bringing with it the threat of hail storms and possible thundershowers.

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The highest peaks around the Bay may also get a healthy dusting of snow above 3,500 feet. Snow showers had left Mt. Diablo and Mt. Umunhum covered in snow.

“When it`s all said and done a few inches (of snow) will be possible over the higher peaks of the North and East Bay and Santa Cruz Mountains,” the weather service said.

Snow also fell in the higher elevations of Lake County near Middletown.

Raw video of Lake County snowstorm


PG&E was also advising customers to have a plan for inclement weather and be prepared for unexpected power outages.

“An impactful winter storm is on the way and we’re asking customers to have a plan to keep themselves and their families safe,” said PG&E senior meteorologist Evan Duffey. “Our team of meteorologists is closely tracking the weather system and working with our employees in the field to stage resources and ensure we’re prepared to restore power safely and quickly,”

The storm was set to bring blizzard conditions to the Sierra where higher elevations may see snow accumulations of 2 feet or more.

“The most likely timing of white-out conditions are expected ahead and along the surface and upper frontal boundaries,” the weather service said. “Current timing for this is from around 7 a.m. to around 1 p.m. Thursday. This will be the most hazardous period of travel with the heaviest snowfall rates and strongest winds and 2-plus inches per hour.”

Accumulations of 6-to-12 inches at lower elevations with 10-to-18 inches above 7000 feet and up to 24 inches along the Sierra crest.

Travel will be extremely hazardous on the upper passes of Highway 50 and I-80. Travelers will be forced to use chains and were warned to expect delays.

The weather service has issued a Winter Storm Warning and an Avalanche Watch for the Lake Tahoe area beginning at 7 a.m. Thursday.

“Periods of high avalanche danger may occur from Thursday morning through Friday morning,” the weather service warned. “Forecast heavy snow and high wind may result in widespread avalanche activity in the mountains.”

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The storm also closed all schools in the Tahoe Truckee Unified School District on Thursday, as well as the schools in the Incline Village area of the Washoe County School District.