Narrative:

Line of thunderstorms showing on the radar while cruising at FL370. According to the radar we had about 50 mi of space between 2 cells in which to fly through. This was confirmed by visually locating the tops -- 1 to the south, and 1 to the north, as we flew eastbound. No thunderstorms could be seen or were painting on the radar at any altitude in our path. However, as we passed between the 2 cells we encountered IMC conditions in the cirrus clouds that were originally below us. After about 5 mins in the cirrus we encountered moderate and possible severe turbulence for about a min. Prior to this, we had only been encountering continuous light and occasional moderate turbulence. The aircraft hit an updraft at one point and our altitude increased 800 ft. We immediately corrected back to our assigned altitude of FL370. We notified ATC of the WX problems and they said the best route was direct ft smith for thunderstorm avoidance. We accepted the clearance and the turbulence subsided to continuous light. No other heavy turbulence was encountered. No conflict with other aircraft occurred and the flight landed in memphis without incident or any crew or passenger injuries.

Related reports:

Google
 

Original NASA ASRS Text

Title: ACR LGT EXPERIENCES A LOSS OF ACFT CTL AND ALT EXCURSION WHEN FLYING BTWN 2 CELLS IN A LINE OF TSTMS. RPTR CITES MODERATE TO SEVERE TURB, NO INJURIES. AN INSPECTION OF THE ACFT WOULD HAVE BEEN REQUIRED UPON LNDG AT MEM.

Narrative: LINE OF TSTMS SHOWING ON THE RADAR WHILE CRUISING AT FL370. ACCORDING TO THE RADAR WE HAD ABOUT 50 MI OF SPACE BTWN 2 CELLS IN WHICH TO FLY THROUGH. THIS WAS CONFIRMED BY VISUALLY LOCATING THE TOPS -- 1 TO THE S, AND 1 TO THE N, AS WE FLEW EBOUND. NO TSTMS COULD BE SEEN OR WERE PAINTING ON THE RADAR AT ANY ALT IN OUR PATH. HOWEVER, AS WE PASSED BTWN THE 2 CELLS WE ENCOUNTERED IMC CONDITIONS IN THE CIRRUS CLOUDS THAT WERE ORIGINALLY BELOW US. AFTER ABOUT 5 MINS IN THE CIRRUS WE ENCOUNTERED MODERATE AND POSSIBLE SEVERE TURB FOR ABOUT A MIN. PRIOR TO THIS, WE HAD ONLY BEEN ENCOUNTERING CONTINUOUS LIGHT AND OCCASIONAL MODERATE TURB. THE ACFT HIT AN UPDRAFT AT ONE POINT AND OUR ALT INCREASED 800 FT. WE IMMEDIATELY CORRECTED BACK TO OUR ASSIGNED ALT OF FL370. WE NOTIFIED ATC OF THE WX PROBS AND THEY SAID THE BEST RTE WAS DIRECT FT SMITH FOR TSTM AVOIDANCE. WE ACCEPTED THE CLRNC AND THE TURB SUBSIDED TO CONTINUOUS LIGHT. NO OTHER HVY TURB WAS ENCOUNTERED. NO CONFLICT WITH OTHER ACFT OCCURRED AND THE FLT LANDED IN MEMPHIS WITHOUT INCIDENT OR ANY CREW OR PAX INJURIES.

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.