Scooby Snacks, according to the latest issue of AEA Recommendations for De-icing/Anti-icing of Aircraft on the Ground, Edition 15, September 2001, it appears that the holdover time after a Type I de-ice/anti-ice, one-step procedure is 6 minutes for light snow to 3 minutes in moderate snow.
There is a note in the holdover time table stating that these limits may be further reduced when the aircraft skin temperature is lower than OAT as in your case.
I believe these tables have been revised in this new issue and in fact Type I fluid is now almost exclusively used as a de-icing fluid since the holdover times for anti-ice purposes are not practical any longer.
[ 02 February 2002: Message edited by: 320DRIVER ]</p>