I can only recall one time where snow/ice accumulation on my dish caused me to lose signal. There might have been other times where it was a problem briefly I wasn't aware of, or reduced the signal to the point where it was close to being lost.
Having the dish located over the part of the building where the restaurant's kitchen is may help, it is about 15' from the hood vent which discharges a lot of warm air.
All I know is that where it is makes it completely inaccessible if it ever does get iced up, or need repair in the winter, so when I have my roof redone next spring I'm going to have it located near the eave over the back door leading into the kitchen - then the manager can send one of the kitchen guys with the ladder to brush off the snow if that ever becomes necessary lol.
I just need to get one of those apps that shows the satellite locations so I can make sure that location isn't blocked by the hood or one of the roof AC units - and make sure when I have the antenna replaced it isn't in the LOS either. Plenty of time to figure it out, I've been closed with Directv suspended for 10 months now and counting...