053
AWUS01 KWNH 180558
FFGMPD
WIZ000-MNZ000-IAZ000-NEZ000-SDZ000-181200-

Mesoscale Precipitation Discussion 0953
NWS Weather Prediction Center College Park MD
157 AM EDT Mon Aug 18 2025

Areas affected...Southeast SD...Northeast NEB...Northern
IA...Southern MN...Western WI...

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

Valid 180600Z - 181200Z

SUMMARY...A muddled mess of shortwave, warm advection and
small/storm scale forcing within a solidly unstable/deep moist
environment should result in widely scattered thunderstorms with
some weakly organized clusters capable of short-duration training
elements.  Widely scattered incidents of flash flooding remain
possible through late overnight period

DISCUSSION...Regional RADAR mosaic denotes two weakly organized
shortwave features. The leading one having driven stronger
thunderstorms and scattered flash flooding is progressing out of
southeast MN into NW WI with the convergent banding noted from
north-central IA through to the eastern quadrant of the shortwave
into west-central WI.  The second flatter west to east wave across
southern SD is driving some smaller clusters with weakening bowing
elements and trailing convergent thunderstorms in the eastern Sand
Hills of NEB.

Both reside in a broad southerly low level jet providing some
moisture flux and isentropic ascent/convergence along stationary
front that extends from east of KPIR to south of KFSD and through
northern IA before angling southeastward from a weak surface
inflection west of KALO southward into IL near KGBG.  Surface Tds
remain well above average ranging through the 70s with spots of
75-77F pooled along it.  This results in 1.9 to 2.1" total Pwats
along its length; though stronger LLJ to 25-30kts west of the
Missouri River is increasing moisture ahead of the western,
upstream wave.   Environment remains fairly unstable with ample
well of 2000-3000 J/kg of MUCAPE for any areas of forcing focused
enough to break through minimal capping with isentropic
ascent/convergence along the front.  Instability pool is a bit
deeper and extends northward through the isentropic ascent further
west with the stronger LLJ.  Here rates are likely to be stronger
up to 2"/hr but forward propagation may limit overall duration.
Deep layer westerly flow aloft may also allow for some
short-duration training/repeating across NE NEB/SE SD into NW IA;
which will likely be necessary for localized totals over 3" in
3-4hrs.  These higher rates/totals will be more necessary across
an area with higher FFG due to recent very dry conditions.  Still
widely scattered incidents remain possible.

Further east across SE MN/NE IA/W WI...A wedge of
enhanced/confluent flow due to exiting shortwave in MN will allow
a narrow channel along its southern and eastern flank for
additional elevated convection that has some potential for
training/back-building.  As the instability reduces quicker toward
the northeast into central WI, the coverage and intensity will
diminish quickly and likely not exceed the FFG into Northern and
northeastern WI.  However, continued upglide/back-building through
lower FFG due to recent heavy rainfall across southern MN/SE MN
and northern IA may see spots of 2-3" and similarly possible
incidents of scattered flash flooding through 12z.

Overall, confidence is below average for any given location for
flash flooding given above average dispersion of Hi-Res CAM
solutions to the evolution.  Still, the environment remains
solidly conducive that a few incidents of localized flash flooding
are probable, especially over the recently saturated regions north
and east of the surface front.  Scattered 2-3" totals with
isolated 4" totals remain possible through 12z.

Gallina

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

ATTN...WFO...ARX...DMX...FSD...MPX...OAX...

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

LAT...LON   45309238 44819084 43989037 43229057 42659215
            41989427 41269594 41299670 41929730 42359761
            42869792 43839826 44579601 45269474