Warm Fronts

Warm fronts are a shallower and more gentle change of air mass 
than cold fronts.  Warm air behind the front slides in to replace 
the retreating cooler air ahead of the front.  Warm fronts are 
very slow moving at roughly 10 knots.  The polar front jet (PFJ) 
runs parallel to the warm front on the cold side. 

The weather with a warm front is primarily stratiform and 
continuous, with the greatest part ahead of the front in the 
cooler air (Figure 4-4).  Cumuliform clouds and thunderstorms 
can be embedded in these clouds as well.  Visibility is poor 
prior to passage and improves only slightly afterwards.  Ahead 
of the front, pressures fall gradually. After passage, the 
surface pressure can rise slowly or become steady, and then 
will begin to fall again as the following cold front approaches. 
Surface winds are usually from the southeast before passage, 
rotating clockwise to become gusty southwest after passage 
(veering winds)