177
AWUS01 KWNH 291847
FFGMPD
MIZ000-WIZ000-MNZ000-IAZ000-300030-

Mesoscale Precipitation Discussion 0551
NWS Weather Prediction Center College Park MD
247 PM EDT Sun Jun 29 2025

Areas affected...central Iowa through northeast Wisconsin

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

Valid 291846Z - 300030Z

Summary...Storms developing ahead of a cold front will train
through the afternoon. As rain rates intensify to 1-2"/hr, this
training could result in axes of more than 3 inches of rain,
potentially leading to flash flooding.

Discussion...The regional radar mosaic this afternoon shows
showers and thunderstorms expanding rapidly ahead of an
approaching cold front. Although the front is still positioned
well west of the axis of convection, storms are aligning SW to NE
along the convergent nose of a modest LLJ and downstream of an MCV
noted in the GOES-E visible satellite imagery to enhance ascent.
This LLJ, while veering with latitudinal gain, is transporting
robust thermodynamics northward as a ribbon of PWs above 1.5
inches stretches northward into Wisconsin immediately downstream
of the developing convection, collocated with a plume of SBCAPE
above 4000 J/kg. Although ascent is generally modest, this lift
acting into these favorable thermodynamics will continue to
support intensifying cores, with an expansion of coverage also
likely during the next few hours.

Rainfall rates have been estimated above 1.5"/hr via KARX WSR-88D
already this afternoon. These rates will likely continue to
intensify, and both the HREF and REFS indicate a 10-20% chance of
2"/hr rain rates during the next few hours. Short duration
rainfall may be even more impressive as the 15-min HRRR indicates
brief 3-4"/hr rates (0.75 to 1.0 inches in 15 minutes). As the MCV
pushes northeast and the front approaches, shear may gradually
increase to 20-25 kts, suggesting at least modest organization
into multicell clusters is possible, with the CAMs identifying
southern WI as the most likely location for this evolution.
Regardless of any organization, training/repeating cells appear
likely as Corfidi vectors collapse to around 5 kts and align to
the mean wind, indicating that cells will continue to regenerate
within the greater thermodynamics to the S/SW and then track
northeast, impacting the same areas multiple times. With rain
rates of 1-2"/hr or more expected, this could result in 1-3" of
rain with locally higher amounts as forecast by HREF 6-hr rain
probabilities.

Soils across the area, especially in WI and southeast MN, are
saturated above the 95th percentile within the 0-40cm layer
according to NASA SPoRT due to recent heavy rain. This has lowered
FFG to just 1.5-2"/3hrs which has a 20-30% chance of being
exceeded according to the HREF. This further indicates the
potential for these heavy rain rates to result in instances of
flash flooding through the evening, especially during the most
impressive training.


Weiss

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

ATTN...WFO...ARX...DMX...DVN...GRB...MKX...MPX...MQT...

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

LAT...LON   45598869 45488782 44948768 44138806 43268913
            42669017 41979238 42549299 43369292 43969231
            44639129 45308957 45378935