Strong and steady rain could complicate the plans of Thanksgiving travelers and Black Friday shoppers as an enormous storm is expected to sweep across much of the southern U.S. starting Thursday night.

Parts of Texas, Louisiana and Arkansas were already blanketed with rain by Thursday afternoon and another round of showers is anticipated tomorrow, forecasters say.

The massive system is also expected to bring snow to eastern New Mexico and western Texas. 

The dayslong storm is being driven by a ball of low pressure that settled over southeastern New Mexico after passing through the Rocky Mountains, National Weather Service meteorologist Marc Chenard told USA TODAY.

“As the system dove south and east across the Rockies that’s when it kind of intensified,” Chenard said.

Usually, similar weather systems move with the jet streams and travel quickly from west to east across the country, Chenard said. But this system “separated from the northern stream” and “because it was no longer connected with that westerly flow it slowed down and kind of closed off and became this closed low that we’re seeing.”

As a result, parts of New Mexico and Texas could see four to eight inches of snow Thursday night, the National Weather Service said.