I'm not so sure Snow Valley was the "first" to make snow this season, if they're defining "making snow" as testing out the snowguns.
Here is a shot from the mid-Atlantic's own Whitetail Resort on September 15:
I'm pretty sure I caught glimpses of Whitetail testing out the guns before September 15 on Whitetail's web cam, but didn't think to save the image. I saw Whitetail testing out the snowguns on September 20 as well.
What's not clear is whether they're testing out the snowmaking system, or if it was just a hot day and they decided to fire up the guns to cool off a bit.