As the hot half of a topsy turvy Bay Area weather week reached its end Wednesday, the concerns over the pending volatile half eased a bit — at least in terms of what the instability may mean to fire danger.
“It’s a bit of a miracle,” National Weather Service meteorologist Rick Canepa said early Wednesday. “The instability that we expected aloft is interacting with the low pressure off the shore. That’s where the coldest air is, and it’s a very weak low pressure out there. As a result, it’s keeping the volatility over the coastal ocean.”
Translation: The expected dry lightning and potential for wildfires it creates may be replaced by lightning that’s accompanied by soaking rain.
Or the Bay Area may just get a hint of rain without any of the electricity.
It’s all a bit too complex at the moment to look far ahead because of Tropical Storm Mario off Mexico’s Pacific Coast, Canepa said. The remnants from that storm are mixing with the dynamic cooling from the low pressure off the coast.
“That high water vapor content and cooling could produce more storms,” Canepa said. “The wet kind.”
Initially, the weather service anticipated the presence of dry lightning in the region. That weather phenomenon occurs when lightning strikes without the presence of measurable rain. That increases the risk of new wildfires igniting; dry lightning started the 1.32 million-acre August Complex Fire in 2020, the largest wildfire in state history.
Canepa said the weather service is studying progressive weather models as hours pass to get a better idea of just how this pattern will develop. The weather service forecast the next predicted rain for the region is Monday in Santa Cruz. The rest of the region is not forecast to receive any rain until Tuesday.
Still, Canepa said there is equal instability in the immediate forecast.
“With each successive (forecast) model, we should have more of an idea of what to expect,” he said.
In the meantime, temperatures were expected to peak in Concord and Livermore at a humid 96 degrees on Wednesday, while San Jose is likely to get to 87; Santa Cruz 80; Oakland 79 and San Francisco 72. Come Thursday, Concord and Livermore — generally, two of the hottest places in the region — are forecast to peak at 83 as a cooldown hits.
