AWUS01 KWNH 090927
FFGMPD
ILZ000-MOZ000-IAZ000-NEZ000-091500-

Mesoscale Precipitation Discussion 1228
NWS Weather Prediction Center College Park MD
526 AM EDT Wed Sep 09 2026

Areas affected...Southeast Nebraska...Southern Iowa...Northern Missouri...Northwest Illinois...

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

Valid 090930Z - 091500Z

SUMMARY...Repeating scattered shallow thunderstorms with ability
for 1.5"/hr and additional 1.5-2.5" totals continue to pose
possible isolated to widely scattered low-end flash flooding,
mainly as cells move into areas less affected further south.

DISCUSSION...GOES-E 10.3um WV suite continues to show a persistent
WSW to ENE corridor of enhanced deep layer moisture along the
northwest edge of synoptic ridge that dominates the
Mid-Mississippi and Southeast. Additionally, a northern stream
shortwave is digging through the Dakotas with an attendant cold
front through MN to NW IA into Nebaska; further narrowing/
corralling the deep layer moisture axis. RAP analysis and GPS
data shows core of 2-2.25" total PWATs remain over SE NEB into W
IA though localized profiles and CIRA LPW continue to show a core
of drier air along the SW interface of the subtropical moisture
plume from E KS toward NE MO. Still, strong confluent low level
jet from 30-40kts from 850-700mb continues to support isentropic
ascent and upstream convergence for upstream redevelopment, though
there are some hints that 700mb winds are veering a bit further
suggesting eastward motion of the is redevelopment region may be
expected over the next few hours.

The upwind environment also appears to have retained some unmixed, conditionally unstable air with axis of 750-1000 J/kg of MUCAPE
generally coincident with moisture axis. Some air appears to be
overturning with new scattered development over far SE NEB into SW South-central IA with new scattered/cooling tops noted in 10.3um
EIR imagery. This is similar along the main training axis further
north over E NEB into W IA, though coverage is more scattered in
nature than earlier overnight. Downstream the lack of remaining
instability due to multiple rounds appears to be leading to
general warming and broadening of more moderate shield
precipitation across central to E IA, though regional RADAR shows
some stronger bowing segments into SE IA. As such, rain rates
will be further reducing to 1-1.3"/hr with a few occasional
transient spots of 1.5"+/hr possible.

As such, a streak or two of 1.5-2.5" in 2-3 hours will remain
possible. This may still intersect the recently saturated/flooded
areas along and just south of I-80 though trends suggest the best
remaining instability and moisture convergence would be a county
or two south where higher FFG and drier ground conditions exist
more likely resulting in beneficial rains. However, any
intersection with more saturated areas, including from prior days
(SW IA into far NW MO) still present a low-end potential of
exceedance for isolated to widely scattered but localized
incidents of flash flooding through early daybreak.

Gallina

ATTN...WFO...DMX...DVN...EAX...ILX...LSX...OAX...

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

LAT...LON 41809129 41649010 41258940 40718947 40269033
40139239 40099431 40079643 40209714 40949713
41319524 41589347 41749205

$$
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