I guess you're probably all pretty right here.
The IAS corrected for position and instrument error gives CAS
CAS corrected for compression = EAS and EAS corrected for temp and pressure gives TAS. TAS corrected for Wind = GS.
LSS is as mentioned here before given as function of temperature, not pressure. Although a quick change in pressure effects the TAS and therfore the mach number, you can theoretically cross the barrier of 1.0 although I have problems seeing such a rapid pressure change in such a short time, but you never know perhaps if cruising in and out of clouds this does tend to happend.
Therefore if cruising at a given altitude and hence given pressure and temp, a wind gust in conjuction with a jetstream shear the IAS will change momentarily therfore also the TAS and the mach number, so theoretically you can end up in a situation where you cross the M1.0. The effects of this with regard to a sonic boom or structural interference can be discussed as I honestly don't know. But I would suggest that the effects are pretty much the same as a normal mach 1.0 break.
As also mentioned; above the tropopause the inversion layer is pretty stable, but you never know
