Wintry forecast (5)
I believe the answer is:
sleet
'wintry forecast' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sleet that I've seen before include "Rain/ice mix" , "Partially frozen rain" , "Mixture of rain and snow" , "Precipitate evolution" , "unpleasant weather" .)