May 19 2007 Summary - MT

John M. and I spent Saturday late afternoon/early evening chasing in Musselshell County north of Billings, MT – primarily near the Roundup vicinity. We were just west, and then north, of Roundup watching an apparent supercell (SVR warned) weaken as it moved across Golden Valley County. We experienced a quick downward trend with this original cell as it become outflow dominant before it reached Roundup (and before the line later exploded – on that same outflow?). In hopes of additional development with south/southwest extent, we relocated south out of the ~10 mile stretch of mountains into the far southern portion of Musselshell County. The pictures below were taken (looking generally northwest) along Highway 87 a mile or two north of the Musselshell/Yellowstone County border. We observed 2 or 3 very distinct lowerings with the tail end/southwest extent of the convective line, although we couldn't ascertain much in the way of appreciable low level rotation. Thanks to Gregg G. for the phone calls.

704 pm MDT

716 pm MDT

737 pm MDT - Double rainbow, looking east toward back edge of severe-warned line in eastern/southern Musselshell County