SUMMARY...A few supercells are expected to develop from central to
eastern Illinois into western Indiana by mid-afternoon. Large hail
and isolated damaging winds will be the primary threat west, with
tornado potential becoming greater east.
DISCUSSION...Pronounced boundary-layer recovery is ongoing in the
wake of an earlier morning QLCS with robust insolation beneath the
eastern periphery of a central Great Plains elevated mixed-layer.
Low-level convergence along the surface cold front is expected to
strengthen as the nose of an intense mid/upper-level jet overspreads
the boundary through the afternoon. While convective development is
largely expected to remain on the northern gradient of the richer
low-level moisture/larger buoyancy spreading into the Lower OH
Valley, the highly favorable mid to upper-level wind profiles will
support splitting supercell structures as convection matures.
Low-level flow will become increasingly veered near the front from
west to east, suggesting that large hail and isolated damaging winds
should be the primary threat with western extent. The risk for a few
tornadoes will be greater with eastern extent, including potential
for a strong tornado in IN.