"Jim Burns" wrote in message
...
Thank you for pointing this out. The "visable moisture" requirement is
for
in-flight icing, not frost. Temp/Dewpoint at TEB yesterday morning was
M04/M08. Obviously the "collecting surface" was below freezing and the
temp
dewpoint spread was narrow enough for the humidity to sublimate and create
frost on the wings.

Jim

Sounds like we're closing in on an answer, or at the very least reasonably
informed speculation.