This morning we woke up to a covering of a couple of centimetres of snow. It's fairly wet snow: The temperature is just above freezing so it is already beginning to thaw. This is about as much snow as we usually get here, but the less time it hangs around the better. When it's cold the smow doesn't melt and eventually gets compacted into ice which, especially as we are on a hill, is a real nuisance.
I am often asked whether snow on the roof affects the performance of attic antennas. My answer is: Not so as I've noticed. The SWR of my attic antennas remains exactly the same (in fact it changes more on hot days when the attic temperature reaches 40 degrees plus, due to expansion.)
My magnetic loop on 30m did not need any re-tuning this morning and the first APRS packet sent was received by a German digipeater. My 2m APRS gateway is also functioning normally. I've put the K3 and multiband dipole on beacon monitoring duty and the beacons are coming through just as I would expect. In other words, all is normal.
Perhaps if there was a metre or more of snow I might notice a difference. But I think the amount of frozen water the RF has to pass through on the roof is negligible compared to the clouds it must traverse on its way to and from the ionosphere.