299
AWUS01 KWNH 031853
FFGMPD
WIZ000-ILZ000-IAZ000-040100-

Mesoscale Precipitation Discussion 0387
NWS Weather Prediction Center College Park MD
252 PM EDT Mon Jun 03 2024

Areas affected...much of southern and eastern WI and some adjacent
portions of IA/IL

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

Valid 031900Z - 040100Z

Summary...Scattered showers and thunderstorms are expected to
produce 1-2"/hr rainfall rates through the evening, resulting in
localized totals of 2-4". Isolated to scattered flash flooding is
possible, especially given some already saturated soils.

Discussion...Showers and thunderstorms have been ongoing for much
of the day across portions of the Midwest in association with a
slowly advancing warm front. Locally rainfall rates have exceeded
1"/hr at times, but most locations have picked up an inch or less
of rain with this activity. The concern going forward is for
backbuilding of convection within the warm sector, as deep layer
steering flow towards the ENE may result in localized training of
heavy rainfall. The mesoscale environment is characterized by
MLCAPE of 500-2000 J/kg (and spreading northeastward with the
advancing front), precipitable water of 1.2-1.6" (between the 75th
and 90th percentile, per SPC sounding climatology), and somewhat
limited effective bulk shear (20-30 kts).

Hi-res CAMs are in relatively good agreement with the evolution of
convection this afternoon, suggesting a mixture of discrete and
multi-cell clusters with scattered coverage. While the shear is
somewhat lacking, it is more than sufficient to maintain tilted
updrafts with 1-2"/hr rainfall rates on longevity, as efficient
warm rain microphysics look to dominate within the updrafts as
wet-bulb zero heights are around 12k feet (which is interestingly
near the 90th percentile, notably more anomalous than the
precipitable water values). Resulting localized totals of 2-4" are
expected (consistent with HRRR and HREF PMM depictions), and with
6-hr FFGs (Flash Flood Guidance) generally ranging from 2-3"
(given some already saturated soils), isolated to scattered flash
flooding is possible.

Churchill

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

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

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

LAT...LON   45628908 45318788 44518703 43438763 42508846
            42188965 42379054 42069143 42519195 44069077
            45048998