Bay Area weather expected to be a carbon copy of previous week
The Bay Area began to heat up again Monday, just as the final official hours of summer ticked away. The temperature liftoff is likely to bring the hottest places into the upper 90s and the usually comfortable places into the 80s, a heat-up that will be complemented by a healthy humidity.
It is not likely to last long. By Wednesday, isolated rain storms with the chance of occasional lightning and thunder is set to roll into the region, according to the National Weather Service. After a couple of those inclement days, overcast sky with temperatures more in keeping with the autumn — which officially started at 11:19 a.m. Monday — are forecast to arrive.
Sound like a carbon copy of the the previous Bay Area weather week?
“Yes,” NWS meteorologist Roger Gass said, adding that “it’s very similar.”
One difference came late Monday morning when the Bay Area Air District issued a Spare the Air alert for the region on Tuesday. The still air from the humidly hot conditions was expected to keep pollution levels higher than normal. Areas of the Santa Clara Valley, including San Jose, were expected to have enough bad air to be unhealthy for those with respiratory conditions.
The air is expected to be moderately healthy north of San Jose and up to Santa Rosa, the air district said. The agency has issued two Spare the Air alerts this year.
The most concerning part about that forecast is what it will mean in terms of lightning, and whether any of it will be dry. Gass said the chances for lightning will be in the area of the Central California coast and northward, and that expectations will decrease as the system moves north.
“It’s probably anywhere from 15-30% across the North Bay,” he said. “In the East Bay and South Bay parts of the region, the chances are less than 10% that we’ll have any lightning.”
As with last week’s weather, moisture at the upper level of the atmosphere created by the influence of a tropical storm in the southern Pacific Ocean is moving north and mixing the lower-pressure air that caused the cooldown late last week and through the weekend.
Rainfall totals in a handful of Bay Area places a week ago ran from about .01 to .05 inches depending on the area of the region. Similar, if not lesser totals were expected this week, according to the weather service.
Temperatures are expected to dip into the lower 70s in the hottest places by Wednesday and stay there even after the rain passes and the weekend arrives, the weather service forecast. Overcast muggy weather is expected after Thursday through Sunday and into next week.