A powerful spring storm was bringing cold temperatures and a sloppy mix of rain and snow to parts of Colorado and Wyoming on Mother’s Day.

The National Weather Service issued a winter storm warning for most of northern Colorado and parts of southern Wyoming for all of Sunday and for Monday morning.

Forecasters were also warning that strong thunderstorms and possibly tornadoes could develop in eastern Nebraska and Iowa Sunday afternoon. There was a moderate risk of severe weather in the area starting Sunday afternoon and continuing into Sunday night, the weather service said.

In Colorado, snow amounts could vary greatly, but up to 15 inches could fall at higher elevations and 4 to 9 inches could fall at lower elevations, including Denver and other cities along Colorado’s Front Range.

“If we see the total accumulations that we are anticipating from this storm, we are certainly going to see a top 10 May snow event for the Denver metro area,” said David Barjenbruch, a weather service meteorologist in Boulder.

Barjenbruch said a foot of snow had already fallen in the foothills of Larimer County northwest of Denver by Sunday morning, and workers along much of the Front Range can expect a “slushy, sloppy morning commute” Monday.

The weather service also warned that snow could be heavy and wet enough to snap tree limbs and power lines, causing power failures. Winds gusting up to 30 mph could reduce visibility, and slushy roads could be treacherous to drive.

Julie Smith, a spokeswoman for Denver International Airport, said passengers might spend a little more time on the tarmac as crews de-ice planes, but no major airline delays have been reported. Meanwhile, Denver officials plan to deploy up to 70 snowplows overnight to prepare for Monday’s commute.

In southern Wyoming, the storm forced transportation officials to close a 150-mile stretch of Interstate 80 from Cheyenne to Rawlins on Sunday morning.

The weather service said mountainous areas in Wyoming could get a foot or more of snow, and 5 to 10 inches are forecast for Cheyenne and Laramie.

The storm is a product of a low-pressure system moving east colliding with a cold air mass from the north. It’s expected to deliver rain in the northern plains once it leaves Colorado.

Spring-like weather was expected to return to the Rockies by Tuesday, with mostly sunny skies and temperatures in the mid-50s in Denver, the high 40s in Cheyenne and the low 40s in Laramie.

(AP)