After doing some experimenting and some advice from Wunderground, I was able to download the flv file and play it later. It seems that Winamp is capable of playing these Flash files OK.
I still wish that there was a way to slow them down a bit. I'll experiment with other players.
I was able to extract the link from the "Embed" string below the Wunderground time-lapse player in the Wundercam Video area. For mine it is:
http://icons.wunderground.com/webcamcurrent/m/i/miraculon/1/current.flv
I suspect that the red/underlined info will differ for your cam.
http://icons.wunderground.com/webcamcurrent/m/i/miraculon/1/current.flv
You will need to substitute your own camera info or better yet just copy/paste the similar info for your own camera on Wunderground.
Greg