Previous Message

https://www.spc.noaa.gov/products/outlook/day1otlk.html

In particular, watch for the cells that pop first. That's your major hail (2-3"+) & tornado threat. Everything will eventually glop together into a strong line.

" Current expectations are for thunderstorms to quickly develop along
the length of the front from central IL eastward into IN, southern
Lower MI, and northern OH by 19-22Z as diurnal heating erodes
lingering convective inhibition. Even though low-level moisture
should remain fairly shallow/limited ahead of the front, a narrow
corridor of 1000-1500 J/kg of MLCAPE (locally stronger possible) is
forecast to be present by mid to late afternoon given sufficient
daytime heating and steepening mid-level lapse rates. Strong flow of
50-60+ kt in the 700-500 mb layer and related deep-layer shear of
similar magnitude will support organized updrafts and supercells
with this initial development. Large to very large hail (2+ inches
in diameter possible) should occur as long as a supercell mode can
be maintained.

A fairly quick transition to more linear structures appears likely
given the frontal forcing, with an increasing threat for scattered
to numerous severe/damaging winds as one or more clusters spreads
east-southeastward across much of the OH Valley into western/central
PA through the late afternoon and evening. Given the forecast
strength of the low to mid-level flow, isolated gusts of 75+ mph may
occur. There is a threat for a few tornadoes as well with both
supercells and embedded mesocirculations within the linear clusters,
although a well-mixed boundary layer should increase LCLs this
afternoon as surface temperatures generally warm into the 70s and
80s. Some guidance suggests a locally greater threat for tornadoes
(perhaps a couple strong) may exist across parts of northern/central
IN/OH with any supercells that can be maintained along/ahead of the
cold front, as low-level shear should be greater across these areas
in association with a 35-50 kt west-southwesterly low-level jet.
However, confidence in this scenario occurring was too low to
include higher tornado probabilities with this update.