First Significant Rain, Snow of the Season Will Persist in Southern California, Southwest into Thursday

weather.com meteorologists
Published: November 20, 2019

The first significant rain and snow event of the season is well underway in Southern California and the Southwest, and while it will bring relief from dry conditions, there could also be localized flash flooding.

A southward plunge of the jet stream along the West Coast and an upper-level area of low pressure will continue to bring the chance for precipitation to the Southwest through Thursday.

Locally heavy rain will increase the risk of flooding at times, and snow will pile up in the higher elevations.


Current Radar, Watches and Warnings

Some roads were flooded in Southern California on Tuesday. A portion of Highway 243 near Idyllwild, California, had been washed away from heavy rain, according to a report relayed by the National Weather Service.

As of Wednesday morning, 2.32 inches of rain had been measured in Valley Center, California. In just 30 minutes Wednesday afternoon, 0.78 inches of rain fell near Deer Valley, Arizona.

Vehicles were reported stuck due to flooding along State Route 62 in the Mojave Desert early Wednesday. Motorists were stranded along Highway 177 north of Desert Center, California.

(LATEST NEWS: Wet Weather Floods Roadways in California, Arizona and Utah

Wet Forecast

Rain will continue in parts of Southern California and much of the Southwest through at least early Thursday. Snow will fall in the higher elevations of the Sierra Nevada and Rockies.

The chance for rain and higher-elevation snow will continue through Thursday in much of the Four Corners region.

(MAPS: Weekly Planner


Late Week Forecast

In Southern California, additional rainfall of an inch or less – with locally higher amounts – is expected below snow level (about 6,000 feet in elevation) in the far southwestern portion of the state, including the San Diego area.

Additional rainfall of 1 to 3 inches is forecast in parts of Arizona through Thursday, with some locally higher amounts possible in the mountains north and east of Phoenix. The Phoenix Valley is expected to pick up double or more its average November monthly rainfall (0.65 inches) in about 48 hours.


Additional Rain and Snow Forecast

Precipitation will be spread out over several days, so widespread flash flooding is less likely, but could occur in some heavier downpours.

Flash flood watches have been issued by the National Weather Service from extreme Southern California into much of Arizona, southern Utah and extreme southern Nevada. Flash flooding is possible in these areas, particularly in normally dry washes and urban areas. Debris flows are also possible near steep terrain or below recent burn areas.


Flood and Winter Weather Alerts

Several inches of snow will also pile up in the Sierra, with more than a foot possible in the higher elevations of southern Utah, southern Colorado, Arizona and northern New Mexico.

Winter storm warnings have been posted by the National Weather Service for the southern Sierra, the San Bernardino and Riverside County mountains, parts of extreme southern Nevada, southern Utah, southern Wyoming, western Colorado and southeastern Arizona.

First Significant Rain and Snow of the Season

This is the first notable precipitation in this region so far this wet season, which typically begins in November and lasts through April.

More than 80% of California is at least abnormally dry, according to the latest U.S. Drought Monitor, since precipitation has not fallen this wet season. This is a big jump from Nov. 5, when less than 18% of the Golden State experienced abnormally dry conditions.

Los Angeles and San Diego average around an inch of rainfall from Oct. 1 through Nov. 15, but they did not receive any rain during that period. It has been the eighth-driest start to the water year in downtown San Francisco, where only 0.03 inches have been measured, and it does not appear much, if any, rain will fall there with this upcoming system.

Drought conditions have also developed and expanded in the Four Corners region since late summer due to a relatively dry monsoon season in Arizona and New Mexico, according to the U.S. Drought Monitor.

Drought conditions cover about a quarter of the West.


(U.S. Drought Monitor)

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.


The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.