960
AWUS01 KWNH 080627
FFGMPD
MNZ000-IAZ000-NEZ000-SDZ000-081200-

Mesoscale Precipitation Discussion 1223
NWS Weather Prediction Center College Park MD
226 AM EDT Tue Sep 08 2026

Areas affected...Southern Minnesota...Northern Iowa...Southeast
South Dakota...

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

Valid 080630Z - 081200Z

SUMMARY...Low-end flash flooding potential continues with
additional upstream development and repeating environment with
broad area of 1-2" totals with enhanced stripes of 2-3" embedded.

DISCUSSION...GOES-E WV suite shows fairly straight southwesterly
upper-level 100-110kts jet core from N CO/S WY across the ND/MN
line though the jet is also quite diffluent on the southern side
of the jet with best divergence maxima near the SE/IA/MN line
which is just downshear of an embedded shortwave approaching from
central NEB.  As such, the low level flow has responded with 850mb
speed max of 50kts starting to intersect with a stronger cluster
of cells.  The interaction has broadened into a west to east warm
advection wing with additional deep layer convergence expanding
convective development downstream across the MN/IA boarder (noted
by overshooting tops in the broadening cirrus canopy with -75C
temps).  Additionally, low level moisture has pooled due to this
convergence with overall values nearing 2".

A broader axis of conditionally unstable air is oriented more
north to south with core of 2000 J/kg MUCAPE across E NEB into NE
SD, though expanding eastward across S MN/N IA with sufficient
values 1250-1500 J/kg noted in RAP analysis to help maintain
thunderstorm activity over the next few hours.  Additional
upstream development across the Sand Hills of north-central NEB
near the shortwave will also lift into the western edge of the
ongoing convective area to repeat or potentially merge with
ongoing activity across SE SD.   Scattered 1.75-2"/hr rates
embedded within the broader line of 1-1.5"/hr rates and generally
veered 700-400mb steering flow to support a broader area of
additional 1-2" totals with embedded streaks of 2-3" where
repeating/training or strongest cores could reside a bit longer.

Hydrologically, heavy rainfall over the last few days (including
heavy rainfall tonight over SE SD) have further reduced FFG values
across the area with an axis extending from Gregory/Charles Mix
county to NW IA with hourly FFG below 1.5" and 3hr below 2",
though this extends further across S MN/N IA with <2"/hr or
<2.5/3hrs as far east as Dodge/Mower, MN and Floyd county, IA.
As such, scattered incidents of localized flash flooding will
remain possible.

Gallina

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

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

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

LAT...LON   44259461 44169323 43579245 43139259 42809334
            42599425 42499591 42509741 42699861 42959915
            43419896 44019739 44169627