Weather websites that have been used by flight testers to find icing conditions for testing

Commercial web sites that provide real time icing data which has been used successfully in flight tests
A good reference is "An aircraft flight test program in natural icing conditions: part 1—forecasting for the desired meteorological conditions," presented at the American Meteorological Society (AMS) 9th Conference on Aviation, Range, and Aerospace Meteorology, September 2000, and available from the American Meteorological Society.

Flight test safety