Low pressure will continue to weather across southern Ontario today. Some moisture will wrap around this system and spread across the region today through Sunday. In addition, progressively colder air aloft will cause a limited lake response which will aid in the development of some light lake snow downwind of the lakes through Sunday. Snowfall amounts through Sunday should remain light across the entire area.
High pressure will bring a brief break in the winter weather to the region on Monday.
A storm system will develop across the Plains States Monday, then deepen as it moves into the Mississippi and lower Ohio Valleys on Tuesday. Low pressure will also begin to organize near the Mid Atlantic coast on Tuesday. Rain or a wintry mix will spread northeastward across the region late Monday night or Tuesday morning with mainly rain expected through Tuesday afternoon. The rain could be heavy at times.
The Ohio Valley system will move to near Lake Erie by late Tuesday as it begins to phase with the coastal system. The degree of phasing between these systems is handled differently on each model. All of the models do bring colder air into the system Tuesday night which will change precipitation back to snow in most areas. Some warm air could wrap back into the system from the Atlantic Ocean making precipitation type an issue for portions of Pennsylvania and New York on Wednesday.
The mature system is forecast to stall across the eastern lakes from Wednesday through the end of the week while disturbances rotate around it. This will lead to a prolonged period of snowy weather across the eastern Great Lakes. It is way to early to talk about amounts, but some areas could see significant snowfall.
Long range models indicate this system could remain parked over the region through next weekend.
The pattern next week is highly complex and the evolution of the upcoming winter storm is not yet clear. This forecast will continue to be updated and revised as new information becomes available.