725
AWUS01 KWNH 310627
FFGMPD
MNZ000-IAZ000-SDZ000-311200-

Mesoscale Precipitation Discussion 0901
NWS Weather Prediction Center College Park MD
225 AM EDT Fri Jul 31 2026

Areas affected...Eastern SD...Southern MN...Northern IA...

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

Valid 310630Z - 311200Z

SUMMARY...Vertically stacking cyclone will have strong moisture
flux convergence for slow moving thunderstorms near the center and
along the steepening warm-air advective band(s) across S MN/N IA.
Prolonged 1-1.25"/hr rates with occasional peaks near 2"/hr will
support spots of 2-4", with possible highly localized spot or two
up to 5".  Incidents of focused flash flooding will be possible,
especially near and east of the cyclone center.

DISCUSSION...GOES-E WV suite and RAP analysis depict, older
shortwave that translated out of the Rockies yesterday has stalled
over SE SD and is starting to lift northward and merge with the
larger scale shortwave that can be seen well near KPIR sliding in
to replace it, providing a strong downstream zone of dPVA and deep
layer cyclogenesis.  At the surface, a strengthening 1007-8mb low
in SE SD, appears to be slowly occluding as lead cold front is
advancing upon warm front slow to leave the Missouri River Valley
into western IA; the older northern-stream frontal zone is
dropping a stronger cold front through central SD and through the
Sand Hills that will continue to swing through the base as the
main height-falls roll through over the next 4-6hrs; while return
easterly flow across central MN is steepening the isentropes ahead
of the advancing warm front, though with ample moisture in the
upper 60s and low 70s aiding overall deep layer moisture in the
region. Overall Total PWats along and east of the surface to 500mb
trof axis (across E SD) are AoA 2.25" with strong directional
convergence and with winds of 20-30kts from surface to 700mb.

Moisture flux convergence will be key has overall instability
environment continues to diminish with loss of heating.  Warm
sector/warm conveyor belt out of E NEB had be mixed over with
initial convective line, but solid WAA across the warm front and
into the back-shearing TROWAL toward the vertically stacking
cyclone center will continue to maintain pockets of MUCAPE of
500-1000 J/kg.  This will allow for shallow, inner core convection
across E SD into SW MN to have capability of up to 2"/hr though
flare-ups of convection are likely to be short-lived, focused and
transient to next strong convergence zone, though with limited
cell motions, SHaRS-type intense localized rainfall for 1-2 hours
may result in localized 2-4"+ totals and represent the best
opportunities for flash flooding; though broad areas of 1-1.25"/hr
will exist for prolonged periods due to isentropic ascent/mst flux
convergence.

Eastward, strong vertical ascent on those steepening isentropic
boundary into south-central MN and northern IA will also have
stronger vertical depth closer to the warm conveyor/instability
axis.  Rates of 1.5-2"/hr are likely to result in 2-3" totals
closer to the slower cell motions near the cyclone pivot point,
while further south into central IA may have reduced localized
totals due to forward (west to east) cell motions to limit
residency time.

Hydrologically, the area has remained very dry with NASA SPoRT LIS
0-40cm relative soil moisture values below 15% for much of the
area of concern.  If rates are hard enough, the soils could be
more hydrophobic with run-off, but shield precipitation may help
to soften them initially before heavier rates reach most areas.
So hopefully, the slower rates will be more beneficial for most
areas; however, those areas where the inner-core shallow but
intense convective cores reach with 2-5" totals may result in
localized incident or two of possible flash flooding.

Gallina

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

ATTN...WFO...ABR...ARX...DMX...FSD...MPX...

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

LAT...LON   45819658 45739620 45659558 45369419 44689312
            44069270 43069246 42559268 42279385 42179511
            42509536 43489630 43669675 43859719 44439750
            44989756 45379755 45589739 45789700