Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Mon Aug 12 2019
Valid 121630Z - 131200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST IA TO
WEST-CENTRAL IN...
...SUMMARY...
A few tornadoes, a couple possibly strong, and significant damaging
winds will be likely across southeast Iowa through central Illinois,
mainly this evening.
...IA/IL/IN...
An upgrade to Moderate Risk for tornado and/or wind may become
necessary in later outlooks today.
A leading MCV is tracking east into eastern IA with a lingering
surface cyclone centered over west-central IA. This latter feature
should move east into northern IL through this evening. Diffuse
convective outflow from remnant leading MCS over southern IL has
been shunted across southeast to northwest MO. Nevertheless, air
mass recovery is underway north of the boundary into extreme
southern IA and west-central IL. Further erosion of the prior cold
pool amid cloud breaks should yield at least weak to moderate
surface-based buoyancy by late afternoon in IA to northern IL. More
robust destabilization is expected farther south where greater
unimpeded insolation occurs while a plume of 77-81 F surface dew
points is advected north from the Mid-South. Despite relatively warm
mid-level temperatures, the very rich boundary-layer moisture and
surface heating should yield a plume of large buoyancy with MLCAPE
likely reaching 3000-4000 J/kg across much of MO into
central/southern IL.
Renewed thunderstorm development is probable towards late afternoon
near the surface cyclone in southeast IA and during the early
evening to the southeast in central IL within a corridor of
strengthening low-level warm advection. The initial storms will
likely be supercells capable of producing all hazards, given the
enhanced low-level shear/hodograph curvature near the cyclone/warm
front. Hodographs aloft should tend to favor relatively quick
upscale growth, but even semi-discrete supercells will pose a risk
for at least a few tornadoes, a couple of which be may strong. A
forward-propagating MCS should eventually evolve along the MLCAPE
gradient from central IL into central IN where severe wind gusts
will remain a threat before weakening overnight.