Mesoscale Precipitation Discussion 1069
NWS Weather Prediction Center College Park MD
1256 PM EDT Sun Aug 16 2026

Areas affected...Central Illinois through Indiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 161655Z - 162200Z

SUMMARY...Organized thunderstorms over western Illinois should
expand and intensify this afternoon as they shift east through
Indiana. Cell-training is possible with a localized flash flooding
concern rest of the afternoon.

DISCUSSION...An MCS that crosses northern MO this morning is now
over western IL. Ample instability is downstream with SBCAPE of
4000 J/kg. Abundant moisture is pooled ahead of this MCS as well
with PW to 2.1 to 2.2" extending east across central IN. Deep
layer westerly flow will keep the system progressive overall,
though development ahead will locally train and the bookends
should have prolonged heavy rain. Hourly rainfall estimates
currently around 1.5" should increase as activity further
develops. 1hr FFG downstream is around 1.5" over the northern half
of the discussion area while values are closer to 2" over the
southern half.

The warm start of the HRRR and RRFS have this organized activity,
but both kill it despite the unstable/moist environment, so they
are of little help. Much of the discussion area has recovered
fairly well from recent rains with main stem rivers remaining in
flood. Flash flooding is considered possible from the general 1-2"
rainfall expected with this activity through about 22Z.

Jackson

ATTN...WFO...DVN...ILN...ILX...IND...IWX...LMK...LOT...LSX...
PAH...

ATTN...RFC...KRF...MSR...TIR...NWC...

LAT...LON 41028811 40628646 40278506 39628485 38828490
38808575 38578787 38358923 38489066 38939170
39609150 40189147 40629122 40879074