Very localized low

In article , Ron
Garret wrote:

My money is on an updraft too.

OK, I can buy that, I should have made a power reduction to mitigate the
airspeed rather than bringing the nose up. Too much time flying
aerobatics rather than IFR perhaps

I've had about the same thing happen to me flying a C-172SP over
western Vigrinia at 10000, the foothills east of the Appalachians.
Autopilot was on, level, smooth as can be, and within a minute or two I
notice the RPM indicator dropping by about 150RPM, and airspeed going
from about 110 IAS to near 80. Altimeter and VSI both reported level,
and I couldn't detect much of a climb on the attitude indicator either.
Throttle was full in as well. I chalked it up to a downdraft.

--
Guy