I just read and article on N application on wheat. Lots of guys try to get it on while its frozen for obvious reasons however, OSU extension advises against it. Quoted from the article: "A producer may get away with applying N in February on wheat. However university data has not shown a yield advantage for February applications, but results have shown a major N loss and yield reduction from pre-greenup applications.
Why take the risk, just wait until greenup; the wheat does not need most of the N until April and May anyway." - Link: http://www.farmanddairy.com/news/may-want-to-avoid-applying-nitrogen-to-wheat-in-february/47941.html