A storm merger was about to occur around 2200z in eastern MN as a northeastward moving reflectivity tag was moving toward the larger likely severe thunderstorm.  By 2206z after the merger occurred, the azimuthal shear sharply increased in the 3-6km layer, and radar velocity also showed mid-level rotation (not shown).  By 2212z, the azimuthal shear sharply increased in the 0-2km layer, with the low-level velocity (not shown) transitioning to covergent then rotational.