* WHAT...Sub-freezing temperatures as low as 24 to 30 possible. Lower valleys may drop to 20.
* WHERE...Central Yampa River Basin, Lower Yampa River Basin, Upper Yampa River Basin, San Juan River Basin, and Central Colorado River Basin.
* WHEN...From late Thursday night through Friday morning.
* IMPACTS...Frost and freeze conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing.