Altocumulus Castellanus
Crepuscular rays of the setting sun bathe altocumulus castellanus (ACCAS) clouds in their golden glow, as another day ends on the Minnesota glacial prairie. ACCAS is a sure sign of an unstable layer aloft, whether or not any deeper and lower convection ever takes advantage. In the distance, a low stratus band signals the approach of a cold front.
4 N Clarkfield MN (7 Jun 4) Looking WNW