On June 12, 2002 a rapid oscillation within the water vapor field was measured by several instruments deployed at the homestead site within a six-hour time scale. The total precipitable water amount fluctuated by as much as 30% (1 cm) as measured by a Global Positioning System receiver while an AERI temperature and moisture profiling system indicated a rapid drying and moistening within the lower boundary layer with no reflection of this feature within the surface observations. Data will be presented indicating the magnitude and short time scale of the water fluctuation and some hypothesis regarding the genesis of this mesoscale water vapor feature. Results from an MM5 NWP simulation of this event indicate that the model exhibited some skill resolving this geographically small mesoscale water vapor oscillation. Output from the MM5 will be used to aid in diagnosis of the origin of this feature.