Narrative:

Flying VFR at 16500, noticed altitude showed 19500 avoiding entering clouds eluding storm. Used autoplt trim. The large gain in altitude was not intentional. As soon as center asked me to identify, I began an immediate descent. At high speed found a hole at lower altitude VFR at all times and got under the storm system. In order to avoid clouds deviated close to sometimes in restr area. Could not deviate west because of the IFR conditions in that direction. Control switched from ZLC to clover range control. No mention was made of an infraction. They were only helpful since I was under control or flight following. I write this because I'm not sure if the restr area was hot. I had to deviate because of WX to remain VFR. In future, if for any reason I suspect the WX to descend beyond altitude restrictions I will turn back or head down before it can become a problem. My aircraft is perfectly able to handle high altitude. It is certified to 24000 ft. I have experienced large altitude changes over these mountains before, despite having the plane on autoplt. It was unfortunate to have it happen so quickly in this situation. Knowing it can happen around thunderstorm activity I will try to navigation at lower altitudes underneath, rather than over the top. In the past I have, but this time I did not recognize the possibility. I had been at 16500 on a VFR flight for over 1 hour without incident.

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Original NASA ASRS Text

Title: WHILE TRYING TO MAINTAIN VFR, RPTR CLBED INTO THE PCA AT 19500 FT AND DEVIATED INTO R6406A.

Narrative: FLYING VFR AT 16500, NOTICED ALT SHOWED 19500 AVOIDING ENTERING CLOUDS ELUDING STORM. USED AUTOPLT TRIM. THE LARGE GAIN IN ALT WAS NOT INTENTIONAL. AS SOON AS CTR ASKED ME TO IDENT, I BEGAN AN IMMEDIATE DSCNT. AT HIGH SPD FOUND A HOLE AT LOWER ALT VFR AT ALL TIMES AND GOT UNDER THE STORM SYS. IN ORDER TO AVOID CLOUDS DEVIATED CLOSE TO SOMETIMES IN RESTR AREA. COULD NOT DEVIATE W BECAUSE OF THE IFR CONDITIONS IN THAT DIRECTION. CTL SWITCHED FROM ZLC TO CLOVER RANGE CTL. NO MENTION WAS MADE OF AN INFRACTION. THEY WERE ONLY HELPFUL SINCE I WAS UNDER CTL OR FLT FOLLOWING. I WRITE THIS BECAUSE I'M NOT SURE IF THE RESTR AREA WAS HOT. I HAD TO DEVIATE BECAUSE OF WX TO REMAIN VFR. IN FUTURE, IF FOR ANY REASON I SUSPECT THE WX TO DSND BEYOND ALT RESTRICTIONS I WILL TURN BACK OR HEAD DOWN BEFORE IT CAN BECOME A PROBLEM. MY ACFT IS PERFECTLY ABLE TO HANDLE HIGH ALT. IT IS CERTIFIED TO 24000 FT. I HAVE EXPERIENCED LARGE ALT CHANGES OVER THESE MOUNTAINS BEFORE, DESPITE HAVING THE PLANE ON AUTOPLT. IT WAS UNFORTUNATE TO HAVE IT HAPPEN SO QUICKLY IN THIS SITUATION. KNOWING IT CAN HAPPEN AROUND TSTM ACTIVITY I WILL TRY TO NAV AT LOWER ALTS UNDERNEATH, RATHER THAN OVER THE TOP. IN THE PAST I HAVE, BUT THIS TIME I DID NOT RECOGNIZE THE POSSIBILITY. I HAD BEEN AT 16500 ON A VFR FLT FOR OVER 1 HR WITHOUT INCIDENT.

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.