Mesoscale Precipitation Discussion 0643
NWS Weather Prediction Center College Park MD
1231 AM EDT Fri Jul 11 2025

Areas affected...Eastern NEB...Western & Central Iowa...Far
Northeast SD...

Concerning...Heavy rainfall...Flash flooding likely

Valid 110430Z - 110930Z

SUMMARY...Slow moving thunderstorms near mid-level low, with
faster moving cluster crossing central IA.  Additional 2-4" totals
with repeating cells likely to continue localized incidents of
flash flooding.

DISCUSSION...Complex mid-level evolution continues to provide a
favorable environment for strong thunderstorms with high rainfall
efficiency; some locations where convection will be more
progressive but stronger, while others may be weaker, but slower
but both capable of 2-4" add'l totals, likely resulting in
scattered incidents of flash flooding.

GOES-E WV suite shows stronger main wave over southeast SDak,
while a jet max is streaking out of central Rockies supporting an
upstream shortwave crossing southern NEB. Binary interaction
between the systems is leading to the main wave sharpening and
stalling with strong LLJ response with 35-40kts of 850mb flow
crossing out of the Central Plains, intersecting with a stationary
front that extends from the central NEB/KS boarder north to a low
along the Missouri River in far SW IA before extending nearly due
east across southern IA.   Remaining area of highly unstable air
exists at this intersection across SE NEB into southwest/central
IA with 3000-3500 J/kg of CAPE and strong moisture flux bringing
surface Tds into the low 70s and overall total PWats to 2-2.2"
values.  Strong, fairly orthogonal isentropic ascent will continue
to support stronger convection near the low and eastward. 
Clusters will have 2.5"/hr rates, but deep layer steering flow
parallel to the boundary should be quick to limit overall totals
with the initial burst to 1.5-2" though continued upstream
convergence should support back-building and training across
southwest to central IA.   Totals of 2-4" are likely to induce
incidents of flash flooding through to 09z.

NE NEB/NW IA/SE SDAK...
With the deep layer wave stationary, but deepening, the LLJ is
responding by backing back from southerly to southeasterly along
an inverted surface to mid-level trof/TROWAL-like feature along
the Missouri River.  As the undercutting jet streak and associated
vort max moves across S NEB, convection near the main center will
have reduced forward speeds and evolve with similar note to a
SHaRS (Subtle Heavy Rainfall Signature), where cores of cells are
very slow moving, but produce moderate rainfall in weaker
1000-1500 J/kg of MUCAPE; but in exhausting that well have a few
hours to increases those localized totals to 2-4" totals.  Some
weak cell motion further southeast along the trof/TROWAL may
support some repeating as well, but overall more chaotic cell
motions are also likely to induce localize incidents of flash
flooding especially given lower FFG values (1-1.5"/hr & 1.5-2"/3hr
across the Missouri River Valley). 

Gallina

ATTN...WFO...DMX...FSD...OAX...

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

LAT...LON   43429810 43249704 42549493 41919312 41709258
            41269250 40929265 40949417 40999511 41179664
            42249754 42879825 43289847