Overview of warm and cold front passage

Tuesday and Wednesday 27 and 28 April, 2009 saw temperatures fluctuate wildly as a warm and cold front passed over Vermont.The images at right document that passage (see Unisys archive for more maps).

At 0Z 28 April (Fig. 1) a warm front was slowly approaching from the west as soutwesterly winds brought warm, dry air from the southwestern desert states across New York State and into Canada.

Overnight, the warm front would slowly move across Vermont, and by 12 Z was located on the Maine-New Hampshire border (fig. 2). A cold front associated with the same Low pressure system over Quebec approached New England from the west.

This cold front would pass over Vermont within 6 hours, ushering in a much cooler air mass. By 0Z 29 April (Tuesday evening), the cold front had swept over Maine into the Atlantic (Fig. 3).

More links to graphics for this case can be found here.