Issued 340 AM EDT Sat Apr 21 2018 Valid Sat Apr 21 2018 - Mon Apr 23 2018 ...Heavy rain possible over parts of the Southeast, Tennessee Valley, Lower Mississippi Valley, and Southern Plains... ...Heavy snow possible over parts of the Northern Rockies... ...Temperatures will be 10 to 20 degrees below average over parts of the Central/Southern Plains... A storm over the Southern High Plains will move eastward to parts of the Lower Mississippi/Tennessee Valleys by Sunday evening...