Topband: 160 Meters & Down & Snow?

[Joe]

I figured you all would be the best place to answer this.

At this time my ONLY antenna is a full sized 40 meter elevated vertical.
The base is 10 feet up, and the radials slope down to about 2 feet above 
the ground at the far ends.

The SWR is awesome dead flat.

Now I also use this antenna to listen to the AM Broadcast band. It works 
pretty well.

Now all summer, I at times when I just want something to listen to while 
I'm doing something in the shack,
I'll listen to WGN from chicago AM 720. About 150 miles away.

During the day all summer and till this week, it averaged S-2 to S-3 in 
strength.

Then we got about only an Inch of snow. still can see Grass but it's all 
white.

But WOW WGN in the day now is like 20 db over!

Worried the SWR has changed from the snow. But Nope it is still perfect SWR.

Any ideas what might be happening? Where it improved the signal yet did 
not change the antenna electrically?

Joe WB9SBD