A winter-like storm front fueled by tropical moisture from the Pacific began moving into the Bay Area Monday, bringing with it the promise of record-level rains to drench the region’s tinder-dry hillsides.
The National Weather Service forecasted showers half an inch to 1.75 inches for the North Bay and .10 to .60 across the rest of the Bay Area. The heaviest hit area, forecasters predicted, would be the higher elevations of Sonoma County where as much as two inches could fall.
If more than half an inch of rain falls in San Francisco it will not only set a new record but will also top the total for last January – a month that traditionally among the wettest of the year.
Veteran forecaster Jan Null said the stormy weather will only give the region “a brief respite” in the current tinder-dry conditions.
“It will make a short-term difference,” he told KTVU. “It’s brief respite from the sun drying out the grasses and baking the trees.
That any measurable amount of rain fell at all in California is unusual but not unheard of at this time of year. Normally a Pacific high pressure system settles by summer off the Northern California coast and steers storms north into Oregon and Washington.
"Every now and then it doesn't protect us," said Johnnie Powell, a meteorologist with the National Weather Service in Sacramento.
Forecasters who had expected an inch of rain said that moisture still exists in the system, but it did not fall. They compared it with a sponge full of water than gets only partially wrung out. It means more rain will fall in the Sierra when the storm clouds bump up against the mountains, though it's unlikely much of it will fall as snow.
"It's a warm air mass," said Warren Blier, science officer with the Monterey Bay office of the National Weather Service. "There may be some snow at 10,000 feet, but most of the precipitation will be north of Lake Tahoe and the peaks aren't that high there."
While the bulk of the storm was expected to arrive Monday evening and Tuesday, the heavy cloud cover was already causing delays at San Francisco International.
SFO duty manager Joe Walsh said the overcast prompted a ground delay program of about an hour that should last until around noon.
The airport typically can handle about 60 arriving flights per hour, but the low visibility means that number will be cut in half Monday morning, Walsh said.
Watchdogs are questioning an exclusive agreement between the City of Oakland and a non-profit group, tapped to lead a multi-million dollar project to redevelop the area around the Coliseum BART station.