If all goes according to plan, half of Western New York will be wearing t-shirts and shorts, the other half will be breaking out the sweatshirts and hoodies.
A lot of this has to do with a strong high pressure over Greenland allowing an upper low over the Hudson Bay to sink down and usher in cool air from Canada to the Northeast. The key will be the positioning of this low and how far south it digs. The most extreme scenario points to places such as Wilson and Lockport feeling the mid to upper 40s, while Bradford to Jamestown temperatures would be around a summer-like 70F.
As of now, models are having trouble trying to resolve the sharp boundary draped over the area. In other words, proceed with caution. Models are just an idea and/or representation of what will play out in the long run.
Eventually, a surface low pressure system will move to our east and pull cold air in from the north.
As far as precipitation goes, would expect a few showers in the area on Monday and Tuesday under mostly cloudy skies. And yes, flakes could fall in the higher elevations Monday overnight into Tuesday.