California storm to whip up weekend travel trouble in central U.S.
The storm roared ashore in Southern California on Christmas, unloading torrential rain in Los Angeles and even triggering a tornado warning near Santa Barbara. This vigorous weather system will charge to the northeast over the next three days, generating headaches for post-holiday travelers from California to the Great Lakes.
Through Friday, the storm will continue to unleash heavy rain and mountain snow in the Southwest. When it ejects into the Plains Saturday and Saturday night, areas of heavy rain and thunderstorms are likely from Texas to Indiana.
On the cold side of the storm, mainly over the Dakotas and northern Minnesota, blizzard conditions are possible Saturday night into Sunday.
To the east of the storm, unseasonably mild weather - which resulted in numerous records Christmas Day - will continue.
Effects in the Southwest U.S.
As the storm arrived on Christmas Day, wind-swept rains deluged the region around Los Angeles. Rainfall totals of one to three inches were widespread through Thursday morning, including 1.75 inches in downtown Los Angeles. Long Beach even set a Christmas Day record for rainfall, posting 1.03 inches.
Pocket of flash flooding ensued. For example, the LA Fire Department rescued a man stranded in three to six feet of water, according to Los Angeles Times.
Thunderstorms embedded within rainbands generated enough rotation to prompt the tornado warning just to the southeast of Santa Barbara Christmas night, and a second warning in Orange County early Thursday morning. However, no tornadoes were confirmed.
The storm contains unusually chilly air at high altitudes, supporting snowfall in the mountains of Southern California. Heavy snow had closed several highways as of Thursday morning, including Interstate 5 and portions of the 15 Freeway.
Winter storm warnings were in effect for mountains in Santa Barbara, Los Angeles, Ventura, and San Bernardino counties Thursday with amounts of one to feet predicted above 5,000 feet along with wind gusts over 40 mph.
As the storm system barrels east, low-elevation rain and heavy mountain snow are also forecast in Arizona. Flash flood watches are in effect for much of western Arizona through early Friday. Meanwhile, winter weather advisories cover the high elevations in the central and eastern part of the state, for at least several inches of snow.
Flagstaff, Arizona, which received over half a foot of snow on Christmas Eve, is expecting another 5 to 9 inches.
Effects in the Central U.S.
The storm is forecast to re-organize over Kansas on Saturday. Areas of rain and storms, some locally heavy, will streak from the northern part of Texas through the eastern Plains and Midwest and into the Great Lakes. The National Weather Service is predicting widespread rainfall of around an inch in much of the central U.S.
Thunderstorms and heavy rainfall are most likely on Saturday night, from northeast Texas through Wisconsin. Some thunderstorms could turn severe in the southern half of this zone, mainly south of Missouri.
Population centers where some travel delays are possible late Saturday and Saturday night include Dallas, Little Rock, St. Louis, Kansas City, and Des Moines.
By Sunday, the rains from the storm will stretch from the Great Lakes south to the Gulf Coast, with showers reaching the East Coast by Sunday night.
On the cold side of the storm, including northwest Kansas, western Nebraska, and the Dakotas, heavy snowfall is likely starting Friday night and extending throuh the weekend.
Winter storm watches have already been posted for northwest Kansas and western Nebraska for Friday night to Saturday night for up to 4 to 8 inches of snow and ice as well as wind gusts up to 45 mph.
By Saturday night and lasting through Sunday, blizzard conditions could develop in the eastern Dakotas. The wind-swept snow could also creep into northwest and northern Minnesota.
Mild weather ahead of the storm
In the eastern half of the U.S., winds from the south and a rise in jet stream have created unseasonably mild conditions with many areas 10 to 30 degrees warmer than normal Thursday.
Dozens of locations in the central U.S. set record highs on Christmas Day. St. Louis, which hit 70 degrees, had its second warmest Christmas Day on record. Des Moines, which soared to 62, registered its warmest Christmas Day.
Chicago had already broken its record high for Dec. 26 just after midnight, when it was 56 degrees. The temperature there is forecast to soar even higher, reaching the 60s Thursday afternoon. Its average high is 32 degrees.
Numerous locations in the Great Lakes are likely to set record highs Thursday.
The biggest warm anomalies are expected to get pushed south and east of the Great Lakes on Friday and Saturday, before another big pulse of warmth on Sunday.
From the Great Lakes eastward, temperatures are predicted to remain above normal ahead of the storm until its cold front pushes off the East Coast early next week.
Jason Samenow is The Washington Post’s weather editor and Capital Weather Gang's chief meteorologist.