Big weather changes are on the way for the southwestern United States as a wave of colder air will plunge into the region. The colder weather will be ushered in by a significant storm that will trigger gusty winds, rain showers and mountain snow this weekend, including in some areas that haven't recorded precipitation in months.
For Los Angeles, as well as some other locations in Southern California, the pattern has the potential to bring the first rain since the spring. Showers are like to happen in the region on Saturday and Sunday.
If it does rain in Downtown Los Angeles this weekend, it would be the first time since May 18, when 0.14 of an inch of rain fell. Should a shower survive the trip into the deserts, Palm Springs, California, may experience the first downpour since the second week of April when over an inch of rain soaked the city.
"Any rain will be novel and welcomed," said AccuWeather Western Weather Expert Ken Clark.
"While a widespread soaking rainfall is not foreseen in the pattern, enough may fall to help moisten brush, for a short time, that has been highly combustable for so many months," Clark explained.
The 2020 fire season has been the worst on record in California. As of Nov. 4, 2020, 31 lives had been claimed in wildfire-related incidents, and more than 9,000 fires have burned nearly 4.2 million acres, according to the California Department of Forestry and Fire Protection (CAL FIRE). About 4% of the state's approximate 100 million acres of land have been charred.
Even though the rain will bring some benefits to the tinder-dry region, it will also come with some dangers.
Some roads may become very slick as the first rain showers target the region. Oil and other slippery chemicals tend to build up on road surfaces when rain doesn't fall for weeks and months on end, and the mixture could lead to hazards for motorists traveling this weekend.
It is not only rain showers that will pay a visit to Southern California and other parts of the basins and deserts in the Southwest this weekend, including Las Vegas and perhaps Phoenix. Snow is forecast to blanket the Sierra Nevada, the mountains of Arizona, the Wasatch and other ranges in the region.
For much of the Sierra Nevada, the weekend storm will bring the first widespread accumulating snowfall of the season. Lake Tahoe, California, has only received a few snowflakes during a couple of the cold waves that swept through earlier this autumn. It is possible that enough snow will fall along Interstate 80 over Donner Pass, California, to make roads slushy and slippery at times from Friday to Sunday. Up to a foot of snow may fall on the high country of the northern Sierra Nevada.
Winter storm watches were extended through Sunday in the Sierra Nevada by the National Weather Service on Thursday, and the NWS highlighted concerns for snow-covered and slippery roads as well as poor visibility in elevations above 5,000 feet.
"Even some of the ridges and peaks in Southern California may be dusted with a bit of snow this weekend," Clark said.
Snow is also forecast to fall and accumulate around Flagstaff, Arizona, for the first time this season. The city may pick up a few inches of snow on Sunday.
Of course, in order for it to snow in the region, temperatures will have to plummet, and plummet they will from Friday to Sunday.
Following record-challenging heat in Los Angeles, Las Vegas, Phoenix and dozens of other locations in the Southwest on Thursday, temperatures will slide off a cliff spanning Friday and Saturday.
Highs are forecast to reach near 60 F both Saturday and Sunday in Los Angeles -- which is about 15 degrees below the normal high of 75 degrees.
By Sunday, highs are projected to drop to the 50s in Las Vegas and the middle 60s in Phoenix compared to normal highs in the low 70s and at the 80-degree mark, respectively. The last time Phoenix had a high in the 60s was way back in late March.
Cold nights are ahead for the region as well, forecasters said. Downtown Los Angeles could rival the record low of 43 set in 1886 on Sunday night. Temperatures are forecast to dip into the single digits over the Sierra Nevada Sunday night and over the Arizona mountains during Monday night. The record low of 11 for Sunday night at South Lake Tahoe could be shattered.
Anytime there is a dramatic swing in temperature over a couple of days, there are bound to be strong winds. The strongest winds in this case will be right before the blast of cooler air is expected to arrive.
Gusty west to southwest winds will whip across areas from Southern California to western Utah on Friday and from eastern Arizona to much of New Mexico and Colorado on Saturday. Gusts in this swath will frequent 50-70 mph with an AccuWeather Local StormMax™ of 80 mph.
"Winds will not only be strong enough to kick up dust in desert areas but may lead to high-profile vehicle blow-overs, fallen trees and sporadic power outages," according to AccuWeather Senior Meteorologist Brett Anderson.
"The initial round of strong winds ahead of any rain and snow can temporarily cause a surge in wildfire conditions," AccuWeather Senior Meteorologist Dave Samuhel warned.
New fires could be sparked by downed power lines in some cases, and existing fires may behave erratically in the predicted conditions.
Wind advisories are in effect across portions of California and Nevada on Thursday.
The surge of cold air, gusty winds and spotty rain and mountain snow may not be a one-and-done deal. There appear to be multiple rounds of chilly shots that may take aim on the Southwest through the middle of November, but how much rain, snow and cold air that occur with each would only be speculation at this juncture.
In the meantime, the same system sending cold air into the Southwest with spotty rain and snow will help create widespread heavy snow and blizzard conditions from portions of central Idaho to much of Montana and even into the Canada provinces of Alberta and Saskatchewan this weekend. Motorists planning a cross-country trip through this region may want to consider a more southern route as some major highways, such as I-94, may be impassable.