Mesoscale Precipitation Discussion 0732
NWS Weather Prediction Center College Park MD
733 PM EDT Tue Aug 28 2018

Areas affected...SRN WI...SE MN...NE IA...NRN IL

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

Valid 282333Z - 290403Z

Summary...Traditional and longer term flash flood potential
remains over southern Wisconsin and adjacent areas this evening.

Discussion...Radar based precipitation estimates dating back 2 to
3 days showed 8 to near 15 inches of rain had fallen in a narrow
swath across southern Wisconsin and far southeast Minnesota. A few
confirming gauge sites had measured at least 6 to 9 inches from
Houston County, MN, to Marquette County, WI.

As of 2330Z the latest round of convection had suppressed the
instability axis farther south. Robust convection was still lined
up from northeast Iowa to near Madison, WI, with radar-based rain
rates up to about 1.5 inches in an hour as estimated from KDVN,
KARX. Regional mosaics also showed other numerous convective
showers / storms back in the more stable air across central to
northern Iowa, rooted more in the mid levels. Synoptic deep layer
lift is forecast to increase from this region up through southern
Wisconsin this evening, supporting an expansion of additional
rainfall, moderate at times.

Throughout the day the 12Z WRF-ARW, NSSL WRF, and more recent HRRR
runs, particularly the 21Z run - had handled the convection fairly
well. Projecting forward, these models suggest 1 to 2 inches
(isolated higher amounts) of additional rain with the more
surface-based storms in eastern Iowa, northern Illinois, and
southern to southeast Wisconsin. Flash flooding could result in
sensitive basins or wherever training occurs. Farther north the
rain rates will not be as intense, but still look respectable,
with a quarter to half inch per hour, and additional rainfall
totals just over a half inch moving back into extremely saturated
areas in MN/WI and adjacent northeast IA. Many forms of flooding
are likely to continue, and some flash flooding remains possible.

Burke

ATTN...WFO...ARX...DMX...DVN...GRB...LOT...MKX...

ATTN...RFC...NCRFC...

LAT...LON   44518856 44048747 42758769 42108974 41869196
            43269290 43749226 44329021