The chillier-than-usual temperatures that brought with it a cold-weather advisory early Monday won’t stay that way for much longer, according to the National Weather Service. The source for their eventual warmup: Yet another atmospheric river rain system.
“We’re going to have very cold temperatures again (Monday), but it’s gonna start to get a bit warmer Tuesday night into Wednesday morning,” NWS meteorologist Roger Gass said. “The temperatures are going to get warm with the arrival of the rain.”
That appearance by the rain is expected to be fueled by an atmospheric river system approaching from the southern Pacific Ocean. Gass said rain showers are expected to develop by Wednesday and that they will continue “off and on” all the way through the first weekend of the new year.
This system comes on the heels of an atmospheric-river storm that pounded the region on Christmas with rain, heavy winds, a bit of hail and reports of funnel clouds over the ocean.
“We do get them this time of year,” Gass said. “So it’s not out of the ordinary.”
The immediate effect will be to warm the area. The weather service issued a cold-weather advisory that was in effect between 1 a.m. and 9 a.m. Monday, and cold temperatures around the region overnight fell into the mid-to-low 30s. The advisory was in effect in the East Bay interior valleys and hills, and the Santa Clara Valley and hills, including San Jose, as well as in the North Bay interior valleys and areas of Monterey County.
Those temperatures all are expected to be a bit warmer by overnight into Tuesday and significantly warmer when the storm arrives, according to the weather service.
Similar to last week’s storm, the approaching atmospheric-river system is expected to drop heavy volumes of rain. The weather service anticipates that 2½ to 3 inches of rain to soak the North Bay; most areas in that part of the region received at least 3 1/2 inches in the last storm, and some received more than 5 inches.
San Francisco also can expect at least 2½ inches of rain in the next storm, while the South Bay and East Bay regions are forecast to get between 1 and 1½ inches, according to the weather service.
That rain figures to be come without the thunder and lightning and other severe storm elements that came with the Christmas week blast of weather. The winds — which topped 60 mph in parts of the region last week — are not expected to be nearly as powerful.
“We don’t have thunderstorms in the forecast right now, but that’s likely to change as we get closer to the event,” Gass said. “Some of the winds are forecast to be stronger than others, but I wouldn’t anticipate them to be as strong as last week.”