BTW,

if you want to remove that plastic mount from the antenna, then leave on your dashboard in full sun for an hour or so - this will allow it to become flexible enough to carefully bend away from the antenna itself, and soften up the glue - allowing you to carefully separate it with a razor blade. ( I fortuitously discovered this by accident). I'm sure that the defrosting vents would have the same effect if the weather isn't playing nice.

And if you have somewhere under the dash itself that is mechanically safe, then you can just place the antenna in a balloon and tiewrap it to protect it from moisture.