Question from Mesoscale Discussion 1138

The text in question:

This front is oriented roughly parallel to the midlevel winds especially across northeast PA into southern NY and CT, and this is allowing outflow to undercut ongoing convection. A bit more cross-boundary flow exists farther south into MD and northern VA, as well as over eastern MA, and this may aid storm longevity in these areas.

Could someone help elucidate the relationship between the orientation of the front and midlevel winds and what that means for convection?

My guess so far is that areas where the midlevels are more orthogonal to the front will experience greater wind shear, increasing convection, while those areas where the flows align will have less wind shear and less convection.

The part that loses me is the "this is allowing outflow to undercut ongoing convection."

If someone could explain or illustrate (for my visually inclined self) what exactly this means, I would appreciate it.