A storm forecast to affect the Northwest this weekend will split into two parts — and one of the pieces will take aim at Southern California and the southwestern United States, dragging chilly air back into the region by early next week.
The storm is expected to bring some rain and mountain snow, including at pass levels, in the region. Travel hazards will accompany the beneficial rain and snow over the area.
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The storm may tiptoe as it drifts southward across Northern California and part of the Great Basin from Saturday to Saturday night. But, it may have enough strength and moisture to bring 1-2 inches of snow to Donner Pass and the northern Sierra Nevada, with a stray rain shower at lower elevations.
As this storm drops into Southern California on Sunday, it is forecast to strengthen and slow its forward speed enough to tap into Pacific Ocean moisture. Areas of rain and mountain snow will break out and become fairly widespread over the Southwest as a result.
From Sunday to Monday, lower elevations in Southern California, southern Nevada and western Arizona can expect rain showers to develop and become more numerous.
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A heavy amount of rain is not anticipated, but it will likely be the first rain in two and a half weeks in Los Angeles, San Diego and Phoenix. Rainfall on Jan. 21 ranged from a few tenths of an inch to about 0.50 of an inch in coastal Southern California.
Meanwhile, Las Vegas has not had any rain since the storm just after Christmas. The storm after Christmas brought Las Vegas about one-third of an inch with about one-half of an inch in Phoenix and 1-2 inches in Los Angeles and San Diego.
Because of the extended period of dry weather, a buildup of oil and other contaminants on the roads can make for extra slick conditions at the onset of the rain. Once the rain has washed the oils away after a while, roads may become less slippery.
AccuWeather meteorologists warn that the storm will manufacture its own cold air over the Southwest, allowing snow to fall over elevations that will be disruptive to motorists.
“We expect snow levels to dip to around 3,000 feet and perhaps lower,” AccuWeather Lead Long-Range Meteorologist Paul Pastelok said.
Motorists should anticipate slippery travel over the Grapevine with several inches of snow possible over the mountains in the region. It is possible that Cajon and Tejon passes even close for a time. The elevation of the passes are 3,800 and 4,200 feet, respectively.
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“It is possible, depending on the track and strength of the storm, that snow levels dip much lower than the 3,000-foot level,” Pastelok said.
If that were to happen, snowflakes may be seen flying on the hillsides north and northeast of Los Angeles and east of San Diego.
A stronger storm could also bring snow around Las Vegas. Some snow is forecast to fall on the mountains surrounding the region, as well as in the mountains of northern Arizona.
A dose of cold air recently visited Southern California with record lows being challenged or broke in a number of locations.
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San Diego tied a more than century’s old daily low temperature record of 38 degrees Fahrenheit, originally set way back in 1894, on Wednesday morning, according to the National Weather Service (NWS).
“We expect temperatures to return to near average late this week and into the first part of this weekend ahead of the storm,” Pastelok said. “However, temperatures from Sunday to Monday are likely to dip to 5 to 10 degrees Fahrenheit below average.”
Highs in early February are typically in the 60s at low elevations over Southern California and the deserts well inland. Nighttime lows are typically in the 40s to near 50.
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