263
AWUS01 KWNH 170627
FFGMPD
WVZ000-OHZ000-MIZ000-INZ000-ILZ000-IAZ000-171225-

Mesoscale Precipitation Discussion 1311
NWS Weather Prediction Center College Park MD
225 AM EDT Thu Sep 17 2026

Areas affected...Central and Eastern IA...Northern IL...Northern
IN...Central and Northern OH

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

Valid 170625Z - 171225Z

SUMMARY...Locally heavy showers and thunderstorms with some
cell-training concerns may foster isolated to scattered areas of
flash flooding later tonight and through early Thursday morning.

DISCUSSION...The latest GOES-E Proxy Visible satellite imagery
shows convection initiating and expanding in coverage across
portions of eastern IA through northern IL and also downstream
across northern IN and parts of western OH. Increasing warm air
advection overrunning a quasi-stationary front coupled with the
presence of an elevated instability axis is the primary reason for
the convective development.

MUCAPE values of 500 to 1000 J/kg along with a 20 to 30+ kt
southwest low-level jet will combine with PWs of 1.75 to 2.0
inches to facilitate heavy rainfall rates. A further uptick in the
low-level jet is expected over the next few hours, and this will
support an additional expansion of the convective activity. Some
of these rainfall rates may reach as high as 1 to 2 inches/hour
with the stronger cells, and the latest hires multi-model
consensus led by the 00Z HREF/REFS guidance suggests some
cell-training potential along and north of the front. This may
yield some localized 3 to 4+ inch rainfall totals going through
dawn.

Overall, the heaviest rainfall amounts are likely to develop and
focus across areas of eastern IA and northern IL which is where
the nose of the low-level jet is a bit stronger along with the
pooling of stronger elevated instability. This will yield support
in time for somewhat better convective organization and heavier
rainfall rates. However, the latest radar and satellite imagery
shows convection downstream across parts of northern IN and
western OH which seems to be connected in part to the advance of
at least some weak mid-level vort energy in conjunction with the
broader warm air advection pattern.

FFG values across the region are relatively low, and the rainfall
totals over the next several hours will support a threat for
isolated to scattered areas of flash flooding as a result.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...CLE...DMX...DVN...ILN...ILX...IND...IWX...LOT...
PBZ...RLX...

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

LAT...LON   42399123 42278982 42008793 41688575 41418392
            41058162 40528061 39888097 39828157 40148432
            40378607 40618762 40848925 41079138 41379306
            41609391 42109375 42339281