Click on the image below for a loop of the RUC2 analysis. In particular, note how a new trough, cyclonic wind shift, and absolute vorticity maximum develop over northeast Nevada in advance of the trough, cyclonic wind shift, and absolute vorticity maximum over northwest Nevada. If you doubt the discrete propagation, just watch how the position of the cyclonic wind shift jumps from the -2 C isotherm at 1700 UTC to the +2C isotherm at 2100 UTC.
|RUC2 800-mb geopotential height (black contours),|
absolute vorticity (red contours), wind (vectors), and
temperature (color fill). Click to expand and animate.