Narrative:

There was more convective action than reported. Eventually, a SIGMET was issued for this while I was en route. The main problem was up and down draft some windshear that would blow the plane around like a piece of paper. Plus ice. En route MEA's were 13000 ft. ATC moved me up to 14000. Could not maintain because of ice. Asked for lower as soon as possible.

Google
 

Original NASA ASRS Text

Title: SMA PLT ENCOUNTERS ICING, UPDRAFTS AND UNABLE HOLD ALT. REQUESTS LOWER. MEA NOT ALLOW AT THAT TIME. ALTDEV.

Narrative: THERE WAS MORE CONVECTIVE ACTION THAN RPTED. EVENTUALLY, A SIGMET WAS ISSUED FOR THIS WHILE I WAS ENRTE. THE MAIN PROBLEM WAS UP AND DOWN DRAFT SOME WINDSHEAR THAT WOULD BLOW THE PLANE AROUND LIKE A PIECE OF PAPER. PLUS ICE. ENRTE MEA'S WERE 13000 FT. ATC MOVED ME UP TO 14000. COULD NOT MAINTAIN BECAUSE OF ICE. ASKED FOR LOWER ASAP.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.