For those that want to find the WU image manually/standalone, go to WU. Search your city. Under the map, there is Wundermap and Nexrad. Click on the NexRad.
On that graphic, hit the play button so that the image is moving. Then below that, there is a "Save Image". That will pop up another window with the graphic and it's address.
You can play around with the options like rain/snow, how many frames, etc. Then hit the Save Image again with all those options.