Mesoscale Discussion 2049
NWS Storm Prediction Center Norman OK
0655 PM CDT Fri Aug 25 2023
Areas affected…Illinois…Southwest Indiana
Concerning…Severe potential…Watch possible
Valid 252355Z – 260230Z
Probability of Watch Issuance…60 percent
SUMMARY…A severe threat is likely to continue to develop across
central Illinois. Storm coverage will increase over the next few
hours, as a cluster moves east-southeastward across southeast
Illinois and southwest Indiana. Large hail and wind damage will be
the primary threats. Weather watch issuance will likely be needed
across parts of region.
DISCUSSION…Latest surface analysis has an axis of maximized
low-level moisture along a boundary, extending east-southeastward
across south-central Illinois. Surface dewpoints near this axis are
mostly in the 70s, although low 80s F are present in far southern
Illinois and western Kentucky. This is contributing to a strongly
unstable airmass, with the RAP showing MLCAPE in the 4000 to 5000
J/kg range. Thunderstorms have quickly developed near the
instability max in west-central Illinois over the last half hour.
Short-term model forecasts increase convective coverage, and move a
cluster east-southeastward across southeast Illinois and into
southwest Indiana over the next few hours. The instability, combined
with moderate deep-layer shear and steep low-level lapse rates,
evident on forecast soundings, will result in a wind-damage threat.
Supercells will also likely be capable of large hail.
…Please see www.spc.noaa.gov for graphic product…
LAT…LON 38438830 38538743 38878720 39448723 39878774 40258914
40509016 40339051 40119065 39789058 39268981 38438830