Winter weather threatening this week mainly north of London and Niagara however there is a risk of freezing rain across the regions. There may be higher impacts from the rainfall or the odd thunderstorm. A weak disturbance will bring a little snow or rain to most of Southern Ontario today. However, a stronger low pressure system is expected to emerge from Colorado and affect the regions Wednesday and Thursday. Although there is uncertainty with the exact track of the storm, the latest guidance suggests the precipitation may start out as rain and there may be a changeover to freezing rain from Sarnia to London and eastward along the lake Erie shoreline to Niagara Falls Wednesday afternoon or evening. Later Wednesday night there will be rain continuing with total amounts of 15 to 25 millimetres by Thursday evening. There is also a risk of a thunderstorm in the regions on Thursday. Environment Canada meteorologists are watching the evolution of this storm closely. Even a slight northward or southward shift in the track of the low will affect how much freezing rain or rain falls at any particular location. Please continue to monitor alerts and forecasts issued by Environment Canada.