An intense high-altitude weather disturbance — part of the same dip in the jet stream that helped brew a “bomb cyclone” earlier this week in the Pacific Northwest — has brought all sorts of wacky weather to the southwestern United States.
On Thursday, heavy rains and flash flooding targeted Southern California as snow descended to unusually low levels in the High Desert region. Record low temperatures accompanied the winter storm, which stirred up a line of feisty thunderstorms overnight Thursday. Folks in the Phoenix area even started their Friday morning with a tornado warning.
A wintry wallop
Palmdale, a suburb 30 miles north of downtown Los Angeles in Los Angeles County, picked up a rare amount of Thanksgiving snowfall — more than three inches! Snow levels dropped to as low as 2,500 feet as the storm’s pocket of upper-level cold brought an unseasonable chill.
Snow in the California High Desert isn’t unheard of, but plowable snowfall in November seldom occurs. A foot fell over the course of the month in 1964.
Meanwhile, a dusting of snow offered an eerie garnish atop freshly charred vegetation north of Santa Barbara. Days earlier, the landscape had been singed by the Cave Fire. As of Wednesday, it had burned more than 3,000 acres, and was 40 percent contained.
Snow even forced the closure of Interstate 5 north of Santa Clarita.
Totals exceeding several feet were realized in the Sierra Nevada, where the mountains focused moisture and enhanced snowfall. The storm also claimed a number of temperatures that were the coldest on record. Anaheim, Calif., didn’t make it above 54 degrees on Thanksgiving Day.
Thunderstorms don’t visit Southern California and the desert terribly often. But a modestly unstable atmosphere accompanied the high-altitude cold, allowing a few low-topped thunderstorms to develop. Some likely even produced waterspouts well offshore.
A healthy boomer brought small hail to the National Weather Service office in Oxnard, Calif., eliciting excitement from the team of meteorologists before briefly knocking out their electricity:
And overnight, a band of strong to locally severe storms trekked across the California-Arizona border, prompting severe thunderstorm and flash flood warnings.
A pair of tornado warnings were issued Friday morning for eastern parts of the Phoenix metro area. The only reports immediately available were of minor damage; it is unclear whether a tornado actually developed.
Tucson found itself under a severe thunderstorm warning, too. A tornado warning was also issued north of the city for a storm that crossed Interstate 10.
Southern California spends most of the summertime dry as a bone. But when the winter rains arrive, that can change in a flash. Parts of Los Angeles County picked up more than three inches of rain this week.
3.15 inches were measured at the Cogswell Dam in Los Angeles County through Thursday evening, with 2.72 inches at the Gabriel Dam and 2.61 inches at Mount Baldy. Closer to the coast, amounts were a little bit less — Los Angeles International Airport came in just shy of an inch.
If it seems like Los Angeles has been thirsting for rain lately, you’re not imagining things. But that’s how the weather there typically works. From May through October, the airport typically sees less than an inch of rain. That’s over the course of six months. In more than half of years, there is no measurable precipitation through July or August. This year, the airport didn’t pick up any measurable rainfall during July, August or September.
But things change on a dime in the wintertime, starting in November. The airport averages 10.92 inches of rain during the “cold season” from November through April. That equates to about 12 times more rain during the winter months than the summer months. California rainfall really is a game of feast or famine.