Upper-level winds tend to speed up and diverge downwind of a trough. This induces divergence aloft and reinforces cyclone strength. H. Examples of linkage between upper level flow and surface cyclones. Note surface low embedded in the lee of upper-level trough. Note that cyclones are supported and steered by the jet stream configuration.
Cyclones form in central U.S., move eastward.
Blizzard of 1993 is an extreme example. Low pressure forms over western Gulf of Mexico. Strengthens and migrates northeastward with upper level support in the lee of the trough.