For SE Texas today:
Further south from the middle Texas Coast into Southeast Texas, the
environment will become favorable for supercells by around midday.
As surface dewpoints and low-level shear increase, Significant
Tornado Parameter is forecast to peak in the 4 to 5 range by early
to mid afternoon. RAP forecast soundings just west of Houston at 21Z
have 0-3 km storm-relative helicity reaching about 325 m2/s2. This
will likely support a tornado threat associated with supercells that
form and move into the Houston area this afternoon. A small cluster
of tornadoes is expected across southeast Texas. Although damaging
wind gusts will also be possible, this threat will be associated
with supercell downdrafts and should remain isolated. There could
also be a localized large hail threat with supercells. The potential
for severe storms could continue into the evening as a convective
cluster moves from southeast Texas into southwest Louisiana.