Today's and yesterday's warnings in reverse chronological order.
A cool fall airmass has settled over the region. Daytime highs today will only reach the mid-50s to lower 60s. After sunset, skies are forecast to gradually clear with winds remaining light...under 10 mph. With good radiational cooling conditions temperatures will drop efficiently overnight. Low temperatures by sunrise Saturday morning will range from 29 to 37 degrees in Central Oregon...and from 30 to 35 degrees in the Grande Ronde Valley. Therefore, localized freezing conditions are possible. The highest probability for sub-freezing temperatures will occur between the hours of 3 AM to 7 AM Saturday morning.
As a precaution, it is recommended to protect sensitive outdoor vegetation if possible. Anyone planning to spend time outdoors tonight and Saturday morning, including campers and hikers should also be prepared for these cold temperatures.