Series of Storms Bringing Rain and Snow to California and the Southwest; Flash Flood Watches Issued

Quincy Vagell
Published: January 5,2016
A series of storm systems will continue to impact California and other parts of the West through late this week. Periods of rain, heavy at times, could contribute to mud and debris flows while snow piles up in the mountains. The Southwest will also see some much needed rain and mountain snow from this wet weather pattern.
The National Weather Service has posted flash flood watches for parts of California. Various winter storm warnings, advisories and watches have also been posted from California's Sierra Nevada and the mountains of Southern California to parts of Nevada, Utah, Arizona and New Mexico.
(MORE: Latest News on Western Storm Impacts)

Current Radar and Satellite

A powerful Pacific jet stream is directing the series of Pacific frontal systems into the West Coast, and will continue to do so into this weekend.
The first weather system moved through the region Sunday into Monday. This has been followed with another slug of moisture that was tapering off as of Tuesday night. Yet another low pressure system will follow quickly behind that system into Wednesday.
Below is the forecast timeline along with the rain and snow forecasts.

Flood Watches and Warnings

Into the day on Wednesday, moisture that had impacted the West Coast will push east into Arizona, Nevada, Idaho, Utah, southwestern Colorado and western New Mexico.

Winter Weather Alerts

Round 3: Wednesday - Thursday

The next storm will arrive along the California coast Wednesday, with rain and snow impacts continuing into Thursday.

Wednesday's Forecast

As colder air is projected with this system, snow levels are expected to lower. This could result in snow at elevations as low as 4,000 feet in the Tehachapis, San Gabriels and Santa Ana Mountains of Southern California.
The risk of additional localized flash flooding along with mud and debris flows will continue in parts of California.
Additional rain and mountain will also spread to parts of Nevada, Utah, Arizona, Colorado and New Mexico through Thursday.
Behind this system, another rather quick-moving frontal system may target California this weekend.

How Much Rain and Snow?

Through Friday, 1 to 2 feet of snow seems a good bet in much of the Sierra, with over 2 feet in the highest elevations. Heavy snow in excess of 6 inches is possible across some of the higher elevations of northern Arizona Mogollon Rim, the canyonlands of southern Utah, higher elevations of southern Nevada, southwest Colorado and western New Mexico.
The snow will add to a Sierra snowpack that is much more substantial than at the same point last year. According to California's Department of Water Resources, as of Jan. 4, 2015, the central Sierra snowpack was 100 percent or more of average for the season.
(Forecast: Lake Tahoe | Flagstaff)

Forecast Rain and Snow Through Thursday

For rainfall, widespread 1- to 2- inch amounts should be common across much of the California coast (higher totals in the foothills where up to 8 inches is possible), from north of the Bay Area to Southern California, including L.A. and San Diego. Some one-inch-plus amounts should also spill over into the parts of California's central valley, as well as the low deserts of southern Arizona, including the Phoenix metro.
One fact mitigating the flood threat is that rain will be spread out over the course of the week from multiple modest systems, rather than one deep, slow-moving system with a tropical tap of moisture.
However, it seems likely that at least some local flash flooding will occur in urban/poor-drainage areas. Debris flows on burn-scarred hillsides from recent wildfires are also possible. Keep in mind it does not take heavy rainfall to trigger these mud and debris flows.
Since this is a complex setup with multiple storm systems expected to impact the region, continue to check back with weather.com for the latest information.

First Storm System Recap: Icy Northwest, Rain in California and Southwest

Moisture from the first system impacted parts of Oregon and Washington Sunday into Monday, where a mixture of snow, sleet and freezing rain made for rough travel conditions along the I-5 corridor. Dozens of car crashes were reported in the Portland, Oregon, area due to the icy conditions, according to the Portland Police. Parts of the Portland area saw up to 1.5 inches of snow and a quarter inch of ice through late Sunday night.
In the Southwest, Phoenix saw just a little more than a quarter inch of rain Monday, which is more rain than they saw in all of the days combined from Nov. 16 through Jan. 3.
Light amounts of rain fell along coastal California.

Second System Soaks California

Downtown Los Angeles reported 1.61 inches of rain on the day Tuesday, as of Tuesday evening. That's more rain in one day than L.A. had seen in all of October, November and December 2015 combined.
Highway 101 was closed for about a 4 mile stretch on Tuesday, due to debris flow. Elsewhere, boulders and rocks crashed onto the Pacific Coast Highway at Malibu Canyon, damaging four vehicles in the process. Several freeways in Southern California were also closed, including sections of 10, 105, 110 and 405.
(MORE: California Flooding Closes Roadways)

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