Weather doesn't stop at the borders, but you would never know it by looking at an American weather forecast. Our friends north of the border are inundated with our forecasts, but rarely do they actually benefit from the information. Why do our weather maps stop at the border?
The most apparent explanation is that weather forecasting outlets based in the United States have overwhelmingly American audiences, and as such feel no real need to show us their predictions beyond the borders of the lower 48.
Of the many forecasting outlets I asked about this phenomenon, the only one that took the time to respond was The Weather Channel. In an email, TWC's Senior Communications Director David Blumenthal said that meteorologists at The Weather Channel stop forecast maps at the borders mostly for aesthetic reasons — "our maps generally outline the familiar shape of the U.S. to help better display where the weather is within its borders."
He further notes the company's maps often include Canada and Mexico during hurricane season, such as the map above showing which areas were most at-risk during Hurricane Sandy, and that forecasts do show Canada when extreme weather to the north is expected to impact the United States.
During the spring and summer months, some of the most widely-spread forecast maps are severe weather outlooks issued by the Storm Prediction Center (SPC). The SPC falls under the umbrella of the National Weather Service, so its mission is to forecast weather exclusively for the lower 48.
As the agency's jurisdiction stops at the borders, so do its maps.
One of the best examples of the SPC's maps stopping at the border occurred last Tuesday, June 17. The United States saw 346 reports of severe weather during this outbreak, most of which occurred in the form of wind damage/60+ MPH wind reports in New England.
The severe weather didn't conveniently stop at the borders and skip over southern Ontario, of course. The storms were so bad that one spawned a high-end EF-2 tornado that tore a 12-mile-long path between Angus and Barrie, Ontario, about 60 miles north of Toronto.
Most other products issued by the National Weather Service and its related agencies stop at the international borders, as well, with the exception of those issued by the Weather Prediction Center (formerly the Hydrometeorological Prediction Center, or HPC) and the National Hurricane Center.
Our neighbors to the north aren't without their own weather forecasts, of course. Environment Canada is responsible for issuing official weather forecasts in Canada, including severe weather watches and warnings. The country also benefits from The Weather Network, of which The Weather Channel and its parent companies own 30%.
[Images via The Weather Channel and the Storm Prediction Center]