Mesoscale Precipitation Discussion 1067
NWS Weather Prediction Center College Park MD
804 AM EDT Sun Aug 16 2026
Areas affected...Central Illinois and Southern Indiana
Concerning...Heavy rainfall...Flash flooding possible
Valid 161203Z - 161700Z
SUMMARY...A cluster of thunderstorms over south-central Illinois
will continue to shift east in a moisture rich environment.
Cell-training should continue which raises a threat for isolated
flash flooding.
DISCUSSION...NEXRAD regional display shows an active cluster of
thunderstorms tracking south of Decatur, IL in a warm sector south
of a stationary front over northern IL. SBCAPE of 1500 J/kg and PW
of 2.1" is allowing heavy rainfall with deep layer westerly flow
allowing repeating activity. One hour rainfall of 1.5" is
estimated from KILX. This is close to the 1hr FFG. This activity
will continue to shift east on the north side of the persistent
ridge axis over the Deep South.
Areas downstream have not been as wet as areas farther north over
the past several days, though this activity may persist through
eastern Indiana which had exceptional rain during midweek.
Recent HRRR and RRFS runs have little to no rainfall downstream of
the current cluster. Some warming is noted in the latest clean IR
scans, so this activity may yet diminish. However, the axis of
instability downstream does suggest some potential for continued
development. Isolated flash flooding is possible rest of the
morning.