Breakiron photographed the above mammatus cloud near Fredericksburg. The clouds accompanied severe thunderstorms passing through north central Virginia into southern Maryland. Mammatus are often an indicator of high instability, and strong turning of the wind with height in the atmosphere.
Yesterday the right ingredients came together to produce the dramatic sky. The lumbering upper low to our west (see video below) helped generate plenty of spin in the atmosphere while moist, unstable air was drawn north due to the return flow from high pressure offshore.
From the University of Wisconsin Cooperative Institute for Meteorological Satellite Studies: ...water vapor channel data showed the changing signature of a persistent upper level cut-off low lingering over the north-central U.S. during the 23 September – 27 September 2011 period
Fortunately, despite the violent storm clouds, I was unable to find reports of damage.
I’ll leave you with one more of Breakiron’s stunning photos below...