In certain areas of Canada, the weather observation locations are too far apart, so weather information is more "area" presented, based upon predicted weather patterns and area forecasts. Smoke does not always follow the flow and patterns which typical weather does - which I observed first hand. I found a concentrated "front" of smoke ahead of a known weather front. I could see by radar that the weather front had rain, and was not forecast to be less than VMC, but I was stopped by IMC smoke before I reached the rain. The front had somehow concentrated the smoke along the weather front. I diverted, and reported this to the weather office. But, with a hundred or so miles between weather observation points, they had no way of knowing that phenomenon was happening there.