El Niño Charged Jet Stream Brings Series of Storms to California and the Southwest; Flash Flood Watches Issued

Quincy Vagell
Published: January 6,2016
Consistent with what you would expect in a strong El Niño winter, a strong southern-branch jet stream is sending a series of storm systems into California and other parts of the West this week, bringing a plethora of hazardous weather conditions.
In California, periods of heavy rain are contributing to mud and debris flows and causing flooding in the populated coastal cities. Thunderstorms have even caused damaging winds and hail, with at least one reported tornado. Meanwhile, snow will continue to pile up in the mountains, frustrating travelers but benefiting the snowpack essential to the state's water supply. The Southwest will also see some much-needed rain and mountain snow from this wet weather pattern.
(MORE: Latest News on Western Storm Impacts)
The National Weather Service has posted flash flood watches and advisories for parts of California and Arizona. 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.
(INTERACTIVE: Latest Flood Watches and Warnings)

Flood Watches and Warnings

High surf warnings are in effect for the California coast from the Bay Area all the way to the Mexican border. Extremely dangerous conditions are expected at the coastline, with waves of 14 to 20 feet breaking along the beaches Thursday. Everyone is advised to stay away from the shoreline due to the danger of being swept away by these waves.
The first weather system moved through the region Sunday into Monday.
That was followed by another system that came ashore early in the week, bringing heavy rain from the Bay Area on Tuesday, to the L.A. Basin and San Diego on Tuesday and again on Wednesday. For a recap of rainfall totals and perspective on this, scroll below to our storm recap.
That system is now bringing snow and low-elevation rain to the Four Corners region and Desert Southwest.

Current Radar and Satellite

Right behind that, another colder system is pushing into California with more rain and snow impacts continuing into Thursday.

Thursday's Forecast

Snow levels could drop to as low as 4,000 feet in the Tehachapis, San Gabriels and Santa Ana Mountains of Southern California. These levels could be low enough to impact travel on Interstate 5 near the Grapevine north of Los Angeles.
(INTERACTIVE: Winter Alerts)
The risk of additional localized flash flooding along with mud and debris flows will continue in parts of California, particularly near burn areas, near the coast, and also in foothill locations below snow level.
Additional rain and mountain snow will also spread to parts of Nevada, Utah, Arizona, Colorado and New Mexico through Thursday and Friday. Some snow, generally light, may fall as far north as Idaho and the northern Rockies.
Behind this system, another rather quick-moving frontal system may target California this weekend, followed by at least two more systems next week.
(MAPS: 10-day Outlook)

How Much Rain and Snow?

If there is a saving grace, here, it's that each system moves through relatively quickly, not able to tap an impressive pipeline of moisture from the subtropical Pacific. That means heavy precipitation will only fall for short periods of time, limiting its ability to cause severe flooding or major snow-related travel disruptions.
However, through Friday, 6 to 12 inches of additional snow seems a good bet in much of the Sierra, with over 1 foot in the highest elevations.
Particularly impressive additional snow totals of over a foot are likely in some of the higher elevations of northern Arizona's Mogollon Rim. At least 6 inches of snow is possible in parts of 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

In terms of rainfall through Friday, an additional inch of rain is possible over coastal areas of southern California, including L.A. and San Diego with locally higher amounts in the mountains. Some one-inch-plus amounts should also affect the low deserts of southern Arizona, mainly in areas immediately south of the high country, including the Phoenix metropolitan area.
Lighter amounts are expected elsewhere, including central and northern California, where the heaviest rainfall from this week's series of storms has already occurred. However, additional rainfall will return to those areas this weekend.
Expect additional local flash flooding in urban and poor-drainage areas. Debris flows on burn-scarred hillsides from recent wildfires have already been reported in some areas, and more are likely especially in areas of additional heavy rainfall.
Keep in mind it does not take heavy rainfall to trigger these mud and debris flows. Additionally, Wednesday morning served as a reminder that earthquakes can trigger landslides, particularly when hillsides are destabilized by heavy rainfall.
(MORE: Landslides Reported After Quake Hits Soggy California)

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.

Caltrans crews work to remove a mudflow that closed Highway 101 near Ventura, California, Tuesday.
(Ventura Police Department)

Second System Soaks California, Southwest

Downtown Los Angeles reported 1.61 inches of rain Tuesday. That's more rain in one day than L.A. had seen in all of October, November and December 2015 combined. San Diego's Lindbergh Field also picked up an impressive 1.90 inches of rain Tuesday.
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)
At least seven debris flows were reported to National Weather Service offices in California Tuesday.
On the wintry side, over a foot of snow had already fallen near Pinecrest, California, in the Sierra south of Lake Tahoe. A spotter in the town of Mount Shasta reported backroads resembling "an ice rink" due to freezing rain.
Flagstaff, Arizona, had already picked up almost 10 inches of total snow as of early Wednesday morning.

Wednesday Brings Severe Storms, More Flooding

During the morning, gusty winds blew a double wide trailer off of its foundation near Paso, California. Winds gusted up to 61 mph at Beverly Hills. Small hail pelted a few locations near the coast of central to Southern California, including some suburbs of Los Angeles.
A line of strong to severe thunderstorms came ashore across San Diego County Wednesday afternoon, causing damaging winds up to 62 mph at a mesonet station near Carlsbad. On the south side of San Clemente, numerous residents reported a tornado with damage to at least one home.
Thunderstorm winds were strong enough to knock down trees over parts of Ventura and San Diego counties, including sections of the city of San Diego, although damage was relatively minor and not widespread.
Rocks and other debris washed onto Del Dios Highway in Oceanside. A portion of the 5 Freeway was closed at Avenida Pico due to high water on the roadway, while a part of Highway 39 was closed due to a mudslide in eastern Los Angeles County.
A daily rainfall record was broken on Wednesday at Los Angeles International Airport, after 1.42 inches of rain was reported.

MORE: Seven Wonders of California