Mesoscale Precipitation Discussion 0513
NWS Weather Prediction Center College Park MD
1254 PM EDT Wed Jun 25 2025

Areas affected...northern IA, eastern SD, southern MN

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

Valid 251700Z - 252300Z

Summary...Showers and thunderstorms will gradually expand in
coverage through the afternoon and intensify to support rain rates
of 1-2"/hr. This could produce 2-3" of rain with locally higher
amounts across wet antecedent soils. Flash flooding is possible.

Discussion...The regional radar mosaic this afternoon shows an
expansive area of stratiform rain across Minnesota. This
precipitation is occurring in response to pronounced ascent within
the RRQ of a strong jet streak to the northeast and persistent
warm advection and isentropic ascent along the 850mb inflow axis.
PWs across the region are impressive, analyzed by the SPC RAP to
be 1.5 to 2.0 inches, with the limiting factor to rainfall
intensity so far being the sharp instability gradient as SBCAPE
above 250 J/kg is confined to areas south of the analyzed warm
front. In general, the rainfall this morning has been of moderate
intensity, but a few regions of training across IA, MN, and SD
have resulted in 12-hr MRMS rainfall as much as 3-4 inches and
saturated soils.

During the next few hours, a wave of low pressure developing along
the warm front will track northeast, leading to acceleration of
the downstream low-level wind field. This will result in 850mb
winds surging to 30-35 kts, forcing more pronounced isentropic
ascent as the warm front lifts northward in response. At the same
time, this will draw more intense thermodynamics northward, with
PWs above 2 inches (a daily record if measured) and MUCAPE above
1000 J/kg reaching as far north as the Twin Cities this evening.
This will allow for a rapid expansion of convection as reflected
by high res CAMs simulated reflectivity, and in this robust
environment both the HREF and REFS suggest a high probability
(60-70%) of rainfall rates exceeding 1"/hr, with 15-min rainfall
from the HRRR potentially accumulating to 0.5 - 0.75 inches (brief
3"/hr rates). Although 0-6km mean winds will remain progressive at
20-25 kts, Corfidi vectors aligned to the warm front could produce
2-3 inches of rain, with locally higher amounts above 4 inches
possible.

Rainfall already this morning, as noted above, has been locally
3-4 inches, with widespread 0.5-1 inch also measured via MRMS.
This has saturated the top soils across most of the area according
to the HRRR, likely lowering FFG even beyond the analyzed
1-2"/3hrs. Even in areas that have not been as saturated, HREF
3-hr exceedance probabilities reach 20-30%, further suggestive of
the increasing flash flood risk into this evening. However, the
greatest potential for impacts will be across urban areas or
beneath any longer-term training.


Weiss

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

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

LAT...LON   45749319 45419178 44879111 44159113 43839138
            43339206 42759358 42599531 42819665 43359770
            43919788 44539711 44879628 45339504