Help! My snowblower starts but it doesn't run smooth and the blade looks like it is moving slowly. It sounds like it is getting gas but inconsistently or vroom, vroom vroom. We are expecting a foot of snow tonight. Any thoughts?

Was it stored with a fuel stabilizer? Dry place?
Usually if it surges (the engine) it's the carb has gummed up, gotten trash in it, or water.. or you have a air leak.
Air filter new?

Yes if the snowblower has sat for a bit there is probably a clog in the carb.. running rough is a sign of a lack of fuel.. is it a tecuseh engine? If it is then there is a high speed jet found in the very bottom of the carb... remove it you will find a screw going through a brass bolt the bolt should have three holes one where the screw goes into one real tiny one near the threads and one big one going through the side of the bolt to the other make sure these are arre clear and reinstall should help the running aspect.