I have seen images like the attached "spike feature" from Billings, MT Nexrad in the past and they usually seem to coincide with sunrise and sunset. This one was closer to Noon Billings time on July 2, 2009.

Do any of you weather geeks know what caused this?

I will post an answer that Bill Murray of WeatherBrains was able to provide soon. In the mean time, I would like to hear your ideas!