Same problem here: empty forecasts, errant conditions. Started last night then was corrected. Started again this morning and has been going on for hours. To be clear, I'm getting values returned. Some of them are proper. Most are not (empty or incorrect).
Also seeing this in my app. Out of range values, such as temperatures of 9999. Empty current_observations objects. current_observations with timestamps and data from minutes to days ago. I'm lucky to get 2 good responses per hour.