2023-12-22 20:09:00
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A strong storm is soaking the southwestern United States, bringing flooding that is inundating homes and forcing evacuations. Flood watches blanket Southern California and Arizona as the storm system shifts east, with snow likely in portions of the Four Corners area and the southern Rockies.
More than half a foot of rain fell in Santa Barbara, Calif., swamping an off-ramp from U.S. Route 101 on Thursday. North Salsipuedes Street downtown was flooded with more than six inches of water, with additional runoff gushing out of storm drains that couldn’t keep up with the heavy rain. Nearby, a stretch of U.S. 101 was closed in San Luis Obispo County. Firefighters waded through knee-deep water to reach flooded residenceswith a number of cars mostly submerged.
In some cases, the bursts of rain were “extreme,” according to the National Weather Service. In Santa Barbara, a full inch of rain fell between 8:50 and 9:50 a.m. Thursday, representing its fourth-wettest hour on record dating back to 1948. Interestingly, all 10 of the top 10 wettest hours on record have occurred this century, largely as a result of the increasingly warm and wet atmosphere of human-caused climate change.
The Oxnard civic center reported up to 3.18 inches of rain in a single hour Wednesday night, although that’s not an official Weather Service observation site.
Calendar-day rainfall records were set Thursday at Camarillo Airport, Santa Barbara Airport and the Oxnard National Weather Service office, which received 1.19, 2.60 and 2.78 inches of rain, respectively.
Four tornado warnings were also issued for Southern California as rotating thunderstorms and downpours moved ashore. The Weather Service is warning of more coastal thunderstorms and offshore waterspouts on Friday. Heavy thunder and lightning rolled through areas near Oxnard, with rumbling lasting for hours in some places.
One of the most impressive elements of this storm system has been the amount of rain in the lowlands. For more than 6 inches to fall in Santa Barbara — which is close to sea level — is rather remarkable. Ordinarily, it takes mountains to poke into and focus the moisture held higher in the atmosphere, boosting rainfall rates.
Here’s a roundup of some of the heaviest totals:
- 9.80 inches, East Camino Cielo (mountains northeast of Santa Barbara)
- 8.42 inches, La Granada Mountain in the Laguna Ridge
- 8.16 inches, mountains just north of Montecito
- 6.48 inches, downtown Montecito
- 6.28 inches in Ventura
- 6.09 inches in Oxnard
- 5.87 inches in Carpinteria
- 4.46 inches in Thousand Oaks
- 3.23 inches in Inglewood
- 3.06 inches in Beverly Hills
- 2.95 inches at Los Angeles International Airport
- 1.98 inches in downtown Los Angeles
- 0.55 inches in San Diego
Spurring the widespread downpours is an upper-level low, or pocket of high-altitude cold air, low pressure and spin. That upper-level low is centered just offshore of the U.S.-Mexico border west of San Diego and Tijuana, Mexico. It is gradually churning east and will pass over Arizona on Friday night.
The counterclockwise-spinning low is north of a tongue of rich tropical moisture from the equatorial regions. That’s working into the desert and fueling widespread downpours and a few thunderstorms. Even Phoenix could see up to an inch and a half of rain.
What’s next for the storm
The rain will head into Arizona, spreading over much of the southern half of the Copper State. That could make for dicey travel on Interstates 8, 10 and 17.
By Friday evening, the first wave of downpours will shift east into New Mexico as another batch works into western Arizona. This second batch will be beneath the core of the upper-level low, where chilly temperatures aloft allow surface air to rise and make thunderstorms.
There’s even a marginal (Level 1 out of 5) risk of severe weather associated with any thunderstorms. While the tornado risk is negligible, a few cells in southern Arizona from Yuma to Tucson could produce gusty to locally damaging winds and/or small hail.
As the moisture and storm system shift east into the high terrain of eastern Arizona, 3 to 7 inches of snow are possible above 8,000 feet, with as much as 2 feet above 10,000 feet.
Into the weekend, the upper-level low will pivot northeast, merging with a similar disturbance over the central Rockies. That will bring some mountain snow to Colorado, the Four Corners and portions of the central and northern Plains by Sunday.
Farther south, additional rain and thunderstorms, including a few strong-to-severe storms, are possible over West Texas and the southern High Plains.
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