A storm moving down from Alaska dropped 0.01 of an inch of rain on downtown San Francisco by Monday night, ending a 44-day dry spell that reignited wildfire risk, brought precipitation totals for the water year closer to average and nearly broke records for longest dry streak during the wet season.
Although there hasn’t been significant rain so far, the last time San Francisco and the South Bay received any measurable precipitation was Jan. 8, nearing the 46-day record for days in a row without rain during the winter months, according to the National Weather Service. Monterey and the mountains of Big Sur could receive a quarter to half an inch or rain while other areas are expected to receive a tenth of an inch or less. The rain is expected to continue through Tuesday and taper off by the afternoon.
In the last 24 hours, Middle Peak at Mount Tamalpais and Ben Lomond received 0.12 of an inch of rain as of Tuesday at 6 a.m., while San Francisco got 0.04 of an inch, according to the weather service. It also rained 0.04 of an inch on Mount Diablo, 0.03 of an inch in Redwood City and Fremont and 0.01 of an inch in Oakland and San Jose.
“We’re not expecting a whole a lot of rainfall,” said forecaster Matt Mehle. “As far as the snow, it will be possible over the over the higher peaks of the East Bay but we’re not expecting a whole lot in terms of accumulation. Maybe a dusting on Mount Diablo and near the Lick Observatory.”
The Sierra Nevada also received several inches of snow after a dry January. The UC Berkeley Central Sierra Snow Lab, located at Donner Pass, reported getting 11.1 inches of snow at 8 a.m. over the past 24 hours. The snowfall is expected to continue through Tuesday before ending in the evening or Wednesday morning.
The next chance for rain in the forecast is towards the end of the month but it isn’t sharping up to be a significant system, according to Mehle.
The weather service has also issued a freeze warning from 2 a.m. Wednesday through 9 a.m. Friday for the interior areas of the Bay Area and central coast. Overnight lows could reach the mid 20s to low 30s. Vulnerable populations, including unhoused people who don’t have adequate shelter, are most at-risk during the freeze. The weather service said to look after sensitive vegetation, elderly people and animals. Unprotected outdoor plumbing may also be damaged during the freeze.
San Jose could see temperatures in the mid 30s Tuesday night, while southern parts of the valley near Gilroy and San Martin could reach freezing and the upper 20s. Lows in Livermore and Concord are expected to be in the upper 20s while San Francisco could be in the 30s. The North Bay valleys — one of the most potentially coldest spots in the Bay Area — is expected to see temperatures in the mid 20s near Santa Rosa.
A high-pressure system has pushed any prospective storms into the Pacific Northwest instead of allowing them to drop them down in the Bay Area — typical of a La Niña weather pattern occurring in the Pacific Ocean, in which cold water rises and leads to droughts in western parts of the country. The high pressure system drifted westward a day or two ago, allowing the storm to move down from the north. Severe drought has ravaged Northern California after two dry winters in a row, straining power grids and sparking fires.
After atmospheric river storms in October and December began the water year, which started Oct. 1, on a high note, replenishing the statewide Sierra Nevada snowpack to 168% of normal on New Year’s Day and marking the 21st wettest December on record for San Francisco, which has climate records dating back to 1849. By Friday, the Sierra snowpack dipped down to 70% of normal, according to the California Department of Water Resources.
“We just came out of a potentially one of the longest dry streaks during the wet season,” said Mehle. “The rain that occurred so early in the water is not necessarily favorable. You’d rather have rain spread out throughout the wet season rather than have it all fall at the beginning.”
The dry streak also made wintertime wildfires more likely. The Airport Fire, which sparked five days ago east of Bishop, burned 4,136 acres as of Monday morning.
“From a fire weather standpoint, the lack of rain caused the vegetation dry out,” Mehle said. ‘Even though the rain is a welcomed sight today, it’s not going to erase the dry spell that we went through. We’ll have to be mindful as we head towards spring and things start to dry out.”
Source: www.mercurynews.com