How much rain is coming to Southern California this weekend?
A storm is headed for Southern California, and it is packing much-needed rain and mountain snow to help ease wildfire concerns starting this weekend.
AccuWeather’s California Expert Ken Clark was live on the AccuWeather Network on Jan. 24 to discuss the wildfire threat in California.
A storm is brewing and will deliver much-needed soaking rain to wildfire-ravaged Southern California, snow to the mountains and rain and snow to many areas in the southwestern United States, AccuWeather meteorologists say.
"Despite being smack in the middle of the rainy season, brush conditions over Southern California are currently as dry as they ever get in the summer (the dry season)," AccuWeather California Expert Ken Clark said. "So when you throw dry air and Santa Ana winds into the mix, you have prime ingredients for wildfires."
The Hughes Fire, located northwest of Los Angeles, was the latest large blaze to ignite and rapidly ramp up amid dry and windy conditions. Tens of thousands were forced to evacuate shortly after it broke out on Wednesday.
The last time downtown Los Angeles picked up 0.25 of an inch or greater from a single storm was back in the middle of April. Since the start of the new water year (Oct. 1), there has only been 0.16 of an inch of rain.
The historical average rainfall from Oct. 1 to Jan. 23 is 6.09 inches, so only 2% of the average rain has fallen in L.A. During the most recent dry season, which runs from June through September and can bring some rain on occasion, no rain at all fell in the city.
The upcoming storm from this weekend to early next week should capture enough moisture from the Pacific Ocean to bring a thorough soaking to Los Angeles and much of Southern California, AccuWeather Senior Meteorologist Dave Houk said. Just about every location should get in on some showers, at least, including in the deserts.
How much rain will LA, San Diego get this weekend?
“Rain will return this weekend to Southern California, with the heaviest rainfall expected on Sunday," AccuWeather Senior Meteorologist Heather Zehr said. "Up to half an inch of rain could fall in the coastal areas and valleys. The foothills and lower portions of the mountains could receive 1-2 inches of rain this weekend." The AccuWeather Local StormMax™ rainfall for this event is 3 inches.
The bulk of the rain will fall on the south- and west-facing slopes of Southern California, where moisture-rich breezes will be forced uphill and squeezed out.
This rain will not only dampen dry vegetation that has been fueling wildfires, but some of that moisture will be pulled into the canopy of live brush and trees, which could temporarily make them less susceptible to combustion.
The rain will also help clear ash, particulates and dust out of the air, improving air quality.
While the positives from the upcoming storm will far outweigh the negatives, along with virtually any rain event in Southern California, there are some negatives.
A gentle light rain spread over two to three days would cause little to no trouble in terms of debris flows and rock slides. However, as is often the case with storms that drop southward along the California coast, the rain can focus into two or three rounds where it pours for a while.
"Where downpours linger for more than a few minutes, such as from a thunderstorm," the risk of localized debris flows will increase, especially in recent burn scar locations, where there is no vegetation left to hold back the runoff," Zehr said.
Should thunderstorms bubble up, a couple could even bring small hail.
A more common problem from the storm will be the lack of rain beforehand, which has led to a buildup of oil, dust and even ash on the roads. The mixture of particles and chemicals can make for a slippery sludge that can lead to auto accidents and slip-and-fall incidents.
Snow is coming for the mountains too
The storm will also drag down colder air, and the atmosphere will grow cold enough that snow falls over the mountains, not only in Southern California but over much of the Southwest.
"Snow levels may dip to as low as 2,000 feet over some of the mountain ranges in Southern California, and that means that snow will fall on the passes in the region and roads may get slippery and snow covered," Clark said.
Most snow levels will range from 3,000 to 4,000 feet. However, many of the ridges and peaks in Southern California, including the Transverse Ranges and the southern part of the Sierra Nevada, are likely to pick up several inches of snow to perhaps a foot of snow.
A few inches of snow may also fall on the mountains of northern Arizona with rain showers making a rare appearance across the deserts.
Looking ahead to next week, the storm's slow forward speed may allow some showers to linger in coastal areas of Southern California into Monday and perhaps Tuesday. It now looks less likely that a significant Santa Ana event will develop behind the storm.
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