2011 Ford Expedition

The front AND rear AC blow fine for a little while, then blow almost nothing
from the vents (both front and rear do it at the same time).  The fans (front
and rear) are running just like they were before the air slowed to almost
nothing coming out.  No matter what fan speed I put the selector on, the
blowers will spool up and down just like normal, sounding normally like they
would if the air was blowing out of the vents, but, the air blowing out of the
vents is almost nothing ... no matter what fan selection I put it on.  
When I move it from recirculating air to outside air, there is NO difference.  
Still blows almost nothing, but the fans are running as expected on each fan
selection.
What's going on???