The eastern half of Colorado as well as parts of Wyoming and Nebraska are under a Tornado Watch Wednesday evening as severe thunderstorms roll through the region.

The National Weather Service announced the watch on social media just before 4 p.m. Wednesday, with the advisory valid until 11 p.m. Tornadoes, scattered hail up to the size of a softball and wind gusts as high as 75 miles per hour could be possible while the watch is in effect.

The watch covers Adams, Arapahoe, Weld and Elbert counties, and extends eastward to the Kansas state line and northward to Wyoming and Nebraska, covering nearly two million people, the NWS said.

While the Denver area itself is not covered by the watch, severe thunderstorms and wildfire smoke are expected well into Wednesday night.

As of 4:30 p.m., Denver International Airport was under a ground stop due to crosswinds, with delays averaging 30 minutes and increasing, according to the Federal Aviation Administration.

Nearly 500 flights in and out of the airport had been delayed and 19 had been fully canceled as of 4:30 p.m., according to flightaware.com.