Hi i have a 2000 ford super duty i was plowing snow today and it started slipping in forward gears but revers worked fine then i shut it off and let it set for 4 hours and then we started it and it drove just fine even after it was wormed up what could this be i was thinking maybe the filter is getting plugged any help would be greatly appreciated thanks and god bless.

Not likely. Chances are that while plowing snow, you overheated the transmission, causing the forward clutches to slip. Regardless, you should prepare to replace or rebuild it, keeping in mind that if it is going to be severe duty, such as snowplowing, you will want to add a transmission cooler as well as beefing up your internals. If it slipped once, it will surely do it again, until you lose all forward gears. It will still work great in reverse, in most cases.