YELLOW FREIGHT <YELL> SEES LOWER 1ST QTR NET Yellow Freight System Inc said its expects 1987 first quarter profits to be substantially below the 14.2 mln dlrs or 50 cts a share earned in the same period a year ago. Revenues have been depressed by recent price discounting, added costs from expansion programs, lower shipping volumes and increased costs associated with severe weather conditions on the East coast, company officials told analysts here. An industry-wide rate hike of 2.9 pct, set for April one, will cover Yellow Freight's upcoming labor and other costs but will not make a contribution to operating margins, it said.