High pressure will move eastward away from the area today as low pressure moves toward the area from the northwest. A strong southwesterly flow between these systems will provide the entire area will milder temperatures today on gusty southwest winds. Highs will top out in the mid to upper 40s this afternoon.
Low pressure will deepen while moving eastward from the central Great Lakes, into southern Ontario tonight. This storm system will drag a strong arctic cold front southward across the region late tonight. Ahead of the front, gusty southwesterly winds will continue into the evening hours. Snow showers will break out as the front moves through, and temperatures will drop sharply as winds shift to the west-northwest. Much colder air will spill across the lake by daybreak Sunday with temperatures dropping to the low 20s by that time.
Sunday will be breezy and cold with snow showers likely. Highs will only rebound to the mid 20s. Snow accumulations through Sunday should be fairly light.
Late Sunday afternoon or Sunday evening, a reinforcing arctic cold front will cross the area. Behind this front, true arctic air will flood the region as winds shift to the west-northwest. The winds will become well aligned Sunday night as instability over the lake increases. Snow bands off the lake will organize and become quite intense late Sunday night, continuing through the day on Monday. Gusty winds will whip the powdery snow around creating locally white-outs. Low temperatures Sunday night will dip to the low to mid teens and only rise to the upper teens for highs on Monday.
Significant snow accumulations are possible Sunday night and Monday, especially in areas where heavy squalls persist.
Very cold air will continue to pour across the lake Monday night through Wednesday with a continued threat of lake effect snow showers and squalls.