My guess is that it's a weather balloon, especially since there's a national weather service station nearby, but this is, without a doubt, one of
the oddest things I've seen on a legit "keyhole" type site.
The flash of light you saw in the sky was not a UFO. Swamp gas from a weather balloon was trapped in a thermal pocket and reflected the light from
Venus. [Kay]
Although it looks like a weather balloon to me... well maybe it is ...