The storms will carry the risk of lightning and flash floods as well as heatwaves with muggy conditions, putting emergency services on alert.
A strong ridge of high pressure expanding westward from Mexico, Texas and Arizona is expected to sharply increase temperatures on Wednesday through Friday and draw monsoonal moisture into the region.
The rainfall will not ease the four-year-old drought, said Chris Hintz, a meteorologist with the National Weather Service (NWS) office in Sacramento. “Absolutely not. Not even close.”
In fact the storms will be accompanied by triple-digit temperatures and may trigger wildfires, he warned. “Initially the thunderstorms will probably not produce a lot of rain. They will mainly be isolated and over the mountains. They could produce more fires because of the lightning.”
Jan Null, a former NWS lead forecaster who now runs a consultancy, Golden Gate Weather Services, said monsoonal moisture did not signify torrential, tropical downpour. “It’ll be very spotty. It won’t make a dent in the drought.”
The heatwave began in Sacramento on Tuesday, where temperatures were expected to reach 104F (40C). They could exceed 107F later this week.
July, typically an arid month, has turned out to be one of the wettest in California history. Some of the downpours helped douse wildfires but the accompanying lightning also started about half a dozen new ones.
Storms last week also caused a mud and rock slide on Highway 140 near the western edge of Yosemite park, and washed away a bridge along Interstate 10, a major freeway connecting southern California and Arizona.
Damper vegetation is a mixed blessing for firefighters. It can reduce kindling-type conditions for several days but if heat returns the new, green shoots can quickly die and become fuel for a future fire.
The recent downpours also wreaked havoc on power lines and rained out a Los Angeles Angels home game for the first time in two decades.
Climatologists said there is an increasing chance El Niño, a weather phenomenon characterized by the warming of Pacific Ocean waters, will bring a wetter than average winter to California.
“It’s already in the Pacific, but that doesn’t mean we’ll got a lot of rainfall. But the stronger it gets, the stronger the chance of that happening,” said Null.
There are indications this year’s El Niño could be as strong as or stronger than the 1997-98 El Niño.
Even then, busting the drought will depend on consistent rain reaching northern California, home to giant reservoirs and snowpack which supply the rest of the state.
We will not catch a break here in Kalifornia any time soon…….