02Z 29 NOV 2006 Surface Plot with boundaries
00Z 29 Nov 2006 Surface Analysis (source: NWS)
This exercise is relatively simple in that there is a well-defined front stretching from Iowa southwestward across Kansas into southeast Colorado. North of the front is cooler, drier air. To the east of the front and extending southward across Missouri, Arkansas, into the Southern Plains is warmer air with higher dewpoints. The second challenge is to find the location of the dryline over west Texas. There is vey little wind shift along the dryline (in this case) but there is definite decrease in dew point as you move westward from central Texas toward New Mexico. It is traditional to place the dryline along the 45 degree isodrosotherman.
Note that the NWS surface analysis does not have the dryline on its analysis for 2 hours prior to the surface plot.