Truckers should get ready for another round of Santa Ana winds in California the next couple days.
As high pressure builds into the Great Basin of Nevada, it will push air downward and some of it will move from the northeast to the southwest toward low pressure along the California coast. As the air descends, it will compress and heat up by about five degrees Fahrenheit for every 1,000 feet it sinks, sometimes reaching temperatures of 100 degrees. However, it won’t get that hot with this series of Santa Anas.
At the same time the air descends and heats, it will squeeze through the narrow valleys and mountain passes of the coastal ranges, making it move faster. The effect is similar to partially covering the nozzle of a garden hose which forces the water to spray much faster than it moves through the inside the hose.
As the winds shoot out of the canyons, they can produce wind gusts of up to 70 miles per hour in many instances, making deadheading or hauling light loads especially difficult. But it won’t be easy for other drivers, either. A 70 mile-per-hour gust could broadside a loaded semi truck with 8,600 pounds of force and possibly overturn it. Winds could be this strong in parts of California beginning tonight (Wednesday).
Here’s the breakdown as you plan your routes. Major interstates most affected will be I-5, I-10, I-15, and I-80. You’ll find other affected interstates listed in the sections below, as well as U.S. and state routes.
Northern California
Portions of the Sacramento Valley, the Northern Coastal Range, the west slopes of the northern Sierra Nevada and adjacent foothills, and much of Shasta County:
WIND: North to east at 10 to 20 miles per hour with local gusts of 30 to 35 miles per hour; some gusts up to 45 miles per hour over exposed ridges. Wind will be strongest over ridges and through favorably oriented canyons.
State routes 4, 44, 99, 132, 140, 299, and US-395.
North Bay Mountains and East Bay Hills above 1,000 feet; hills of eastern Napa County and around Mt. Saint Helena, Mt. Tamalpais, Atlas Peak, Mt. Diablo, and Mt. Hamilton:
WIND: Northeast at 15 to 30 miles per hour with gusts of 40 to 50 miles per hour; local gusts of 50 to 60 miles per hour in the highest peaks.
State routes 20, 29, 128, and US-101.
Mendocino National Forest:
WIND: North at 15 to 25 miles per hour with local gusts of 30 to 40 miles per hour on exposed ridgelines.
State route 162.
Southern California
Orange County Coastal areas:
WIND: Northeast at 15 to 25 miles per hour with gusts of 30 to 40 miles per hour.
Interstate 405, state routes 1 and 73.
San Bernardino and Riverside County valleys, The Inland Empire, San Diego County inland valleys, San Bernardino County mountains (Including the Mountain Top and Front Country Ranger Districts of the San Bernardino National Forest), Riverside County mountains (including the San Jacinto Ranger District of the San Bernardino National Forest), Santa Ana Mountains (including the Trabuco Ranger District of the Cleveland National Forest), San Diego County mountains (including the Palomar and Descanso Ranger Districts of the Cleveland National Forest), Orange County inland areas:
WIND: Northeast at 20 to 30 miles per hour, 30 to 40 miles per hour near and below passes and canyons; gusts to 50 to 65 miles per hour.
State routes 74, 78, and 79.
Ventura County interior valleys, Ventura County coastal valleys, Santa Clarita Valley, Los Angeles County San Fernando Valley, Los Angeles County San Gabriel Valley:
WIND: Northeast at 25 to 35 miles per hour with gusts up to 50 miles per hour.
State routes 1, 33, 126, and US-101.
Ventura County mountains/Los Padres National Forest, Los Angeles County mountains/Angeles National Forest:
WIND: Northeast at 20 to 30 miles per hour with gusts up to 55 miles per hour; winds of 30 to 40 miles per hour with gusts to 70 miles per hour Thursday night into Friday morning.
State routes 2 and 39.
Santa Monica Mountains Recreational Area:
WIND: Northeast at 20 to 30 miles per hour with gusts up to 55 miles per hour; winds of 30 to 40 miles per hour with gusts to 70 miles per hour Thursday night into Friday morning.
Kanan Dumme Road and Latigo Canyon Road.
Los Angeles County coast (including downtown Los Angeles):
WIND: Northeast at 15 to 25 miles per hour with gusts up to 40 miles per hour; winds of 20 to 30 miles per hour with gusts to 50 mph near foothills Thursday night into Friday morning.
Interstates 105, 110, 210, 405, 605, state routes (SR) 1, 134, and US-101.
Not only will the Santa Ana winds make driving a challenge, they also kick up sand, dirt, and dust right into the fields of vision of truckers and limit visibility. In addition, the Santa Anas make the air extremely dry, with relative humidity of 15 percent or less. This can cause brush fires and wildfires to easily ignite, and the winds can spread these fires very quickly, up to 5,000 acres per hour. Smoke from fires can also make it hard for truckers to see far enough down the road.
The National Weather Service has issued Red Flag Warnings which last through Thursday for some areas, Friday for others.