For prompt and detailed weather forecasts and road conditions in Winnipeg and southern Manitoba, check out...
University of Manitoba Weather Central.
Here are a few relevant entries for weather forecasts applicable to Manitoba, from Environment Canada's Weather Office.
You may also be interested in the Winnipeg weather forecasts from TimeAndDate.com (by CustomWeather), The Weather Network, Canoe Weather, CBC Manitoba, Intellicast, AccuWeather, Yahoo! Weather, Holiday-Weather, or Weather Underground.