With Thanksgiving holiday travel well underway, many have reached their destinations — but for everyone else, a storm tracking from the Rockies to the Midwest and Northeast into Thursday will bring rain and snow, likely impacting flights and packed roads.

Just shy of 3 million people were expected to be screened by the Transportation Security Administration on Wednesday, and a record 71.7 million were expected travel by car over Thanksgiving — over 1 million more than last year.

The…