Also mentioned possibly a derecho.
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 AM CDT Fri Jul 19 2019
Valid 191300Z - 201200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS EAST-CENTRAL MN
AND NORTHERN WI...
...SUMMARY...
A regional outbreak of severe thunderstorms with strong tornadoes
and potentially widespread significant wind damage may occur from
central Minnesota across northern Wisconsin during the mid-afternoon
to evening.
...Upper Midwest/Great Lakes...
Upgrading to Moderate Risk this outlook for the potential threats of
multiple strong tornadoes and a derecho later this afternoon and
evening. CAPE/shear/SRH parameter space in this region is forecast
to be exceptionally rare for mid July amid a predominately zonal
flow regime across the northern states.
A convective cluster is ongoing across north-central SD aided by
warm/moist advection around 700 mb along a pronounced baroclinic
zone. 00Z CAM guidance had a decent handle on this activity earlier
this morning and are consistent with a decaying trend through late
morning as advection shifts east amid pronounced MLCIN as sampled by
the 12Z Aberdeen sounding. There is a low confidence scenario that a
strong enough cold pool is becoming established with this early-day
cluster such that total decay does not occur. If this occurs, robust
boundary-layer heating downstream may be sufficient for an
increasing threat during the afternoon of strong to severe wind
gusts. This could still yield a scattered to widespread damaging
wind scenario, albeit in an earlier time frame than progged by
guidance.
The more probable scenario is for an extremely unstable air mass
(MLCAPE > 4000 J/kg) to become established to from southeast SD
through central/southern WI as the elevated mixed-layer overspreads
surface dew points rising into the mid to upper 70s. A surface
cyclone over central SD should track towards the Twin Cities through
early evening. Strong low-level convergence near/northeast of this
cyclone along the warm front should sustain surface-based storm
development across central into east-central MN. Once initiation
occurs, intense supercells will develop rapidly, with an attendant
threat for all severe hazards including strong tornadoes amid 50-60
kt effective shear and 0-3 km SRH > 300 m2/s2. The very warm/moist
thermodynamic profiles will also support generation of strong cold
pools which should eventually yield a bowing, forward-propagating
MCS across northern WI into parts of northern Lower and Upper MI.
Strength of the vertical shear suggests the potential for intense
bowing segments capable of yielding a derecho with significant
severe wind gusts