  In the present paper, we study the evolutionary conditions for
Kelvin--Helmholtz (KH) instability in a high-temperature solar surge observed
in NOAA AR11271 using the Solar Dynamics Observatory data on 2011 August 25. We
study the propagation of normal MHD modes in a flux tube considering the two
cases, notably of untwisted magnetic flux tube and the twisted one. The
numerical solution to the dispersion relation shows that the kink ($m = 1$)
wave traveling in an untwisted flux tube becomes unstable if the jet speed
exceeds $1060$ km\,s$^{-1}$ -- a speed which is inaccessible for solar surges.
A weak twist (the ratio of azimuthal to longitudinal magnetic field component)
of the internal magnetic field in the range of $0.025$--$0.2$ does not change
substantially the critical flow velocity. Thus, one implies that, in general,
the kink mode is stable against the KH instability. It turns out, however, that
the $m = -2$ and $m = -3$ MHD modes can become unstable when the twist
parameter has values between $0.2$ and $0.4$. Therefore, the corresponding
critical jet speed for instability onset lies in the range of $93.5$--$99.3$
km\,s$^{-1}$. The instability wave growth rate, depending on the value of the
wavelength, is of the order of several dozen inverse milliseconds. It remains
to be seen whether these predictions will be observationally validated in
future in the coronal jet-like structures in abundant measure.
