National Weather Service Riverton WY 1254 AM MDT Sat Sep 16 2017 ...Possible Freezing Temperatures by Sunday Morning Across the Lower Elevations of Wyoming... .As an early Fall storm moves out of Wyoming today, skies will clear tonight into Sunday morning. This will allow heat to radiate out quickly from the already cool airmass...dropping to near or even well below freezing by around sun-up Sunday morning across the lower elevations of Wyoming. Jackson Hole-Star Valley- Including the cities of Jackson, Afton, Alpine, Star Valley Ranch, and Thayne 1254 AM MDT Sat Sep 16 2017 ...FREEZE WATCH REMAINS IN EFFECT FROM LATE TONIGHT THROUGH SUNDAY MORNING... * TEMPERATURE...20 to 30 degrees. * IMPACTS...Plants may be damaged by the cold morning temperatures. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Freeze Watch means sub-freezing temperatures are possible. These conditions could kill crops and other sensitive vegetation.