After a relatively mild weekend, the large scale weather pattern will undergo some big changes across the country this week.
A large ridge of high pressure will build over the west while at the same time, a deep trough of low pressure will form over the Northeast. This will allow cold air that is currently building in northern Canada to spill south into our region by the second half of the week.
The first surge of Arctic air will arrive Wednesday night into Thursday with highs Thursday struggling to climb into the mid teens. This cold air combined with a northwest wind direction will help generate lake effect snow squalls along the south shore of Lake Ontario, including much of Monroe county. It's still much too soon to say how much snow we'll see but several inches of fluff will be possible.
The second surge of Arctic air will plunge south by the weekend bringing the coldest temperatures we've seen in about a year. Several reliable forecast models we use are showing some truly bitter air arriving.
The GFS model is showing highs not even climbing above zero by Saturday afternoon!