SPC AC 191736
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Thu Jul 19 2018
Valid 201200Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR SOUTHERN
IL/IN...CENTRAL/WESTERN KY...MIDDLE/WESTERN TN...NORTHERN MS/AL...
Scattered severe thunderstorms associated with large hail, wind
damage and a tornado threat will be possible Friday afternoon and
evening across parts of the MIssissippi, Ohio and Tennessee Valleys.
An anomalously strong deep layer trough and associated surface
cyclone are expected to move southeastward from the upper Midwest
into portions of the lower Great Lakes on Friday. The surface
pattern will be complicated by one or more convectively-induced
outflow boundaries, with a synoptic-scale surface trough/cold front
expected to progress eastward south of the surface low through the
period. A stout EML will spread eastward from the southern Plains
over rich low-level moisture, resulting in a volatile thermodynamic
environment developing over portions of the MS/TN/OH River Valleys
and the Midwest.
...MS/TN/OH River Valleys into the Midwest...
A potentially significant severe thunderstorm episode is possible
across portions of the MS/TN/OH Valleys and the Midwest on Friday,
though considerable uncertainty remains regarding convective
evolution through the period.
One or more clusters of convection will likely be ongoing Friday
morning, though the remnants of these clusters are expected to push
east through the day, allowing for moderate-to-strong
destabilization in their wake. The strongest focus for convection
will be the surface trough moving through IL/IN/OH, though this area
will be somewhat removed from the stronger shear and instability,
especially with northward extent.
Foci for convective initiation will be more subtle further south and
west, but the environment will also be much more volatile, with
strong instability (MLCAPE of 2500-4000 J/kg possible) and effective
shear (45-60 kt) in place. Scattered thunderstorms are expected to
develop during the afternoon, potentially along the trailing surface
boundary and also evolving out any early day elevated convection.
Initially discrete storm modes will favor large hail (potentially
greater than 2 inches in diameter), along with damaging wind gusts
and a tornado or two. With time, evolution into one or more
upscale-growing clusters is expected into the evening. Any such
clusters would be capable of producing damaging wind swaths as they
propagate to the southeast.
Confidence in convective initiation is much lower across portions of
northwest AR westward into northern OK and southern KS. However,
very strong heating in the presence of a weak surface boundary may
support isolated development during the afternoon. Additionally,
there is some potential for elevated convection to develop across
this region, either early or late in the period. Given the very
favorable instability/shear environment across this region, a
conditional risk of severe hail and wind will be present across this
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 30% - Enhanced
Hail: 30% SIG - Enhanced
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z