867
AWUS01 KWNH 240915
FFGMPD
WIZ000-ILZ000-MNZ000-IAZ000-241400-

Mesoscale Precipitation Discussion 0314
NWS Weather Prediction Center College Park MD
515 AM EDT Fri May 24 2024

Areas affected...much of IA...portions of southern MN...far
southwest WI

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

Valid 240915Z - 241400Z

Summary...Increasing convective coverage ahead of an approaching
MCS may result in short-term (3-hr) totals of 2-3" locally.
Isolated to scattered instances of flash flooding are possible.

Discussion...A mature MCS has rapidly propagated eastward through
portions of the Central/Northern Plains overnight, recently
crossing the Missouri River into the Upper Midwest/Mid-MS Valley.
The leading edge of the line is moving at over 50 kts, which has
limited the residence time of heavy rainfall rates (thus limiting
the flash flood potential significantly). Over the past several
hours, convection has begun initiating out ahead of the MCS, which
is increasing the concerns for flash flooding into the early
morning hours. This convection is being spurred by strong
isentropic ascent/warm air advection in the low to mid levels,
also evident in the 3-hr MUCAPE increase of 500-1500 J/kg across
much of IA. Likewise PWATs are increasing rapidly to the 1.3-1.6"
range, at or above the 90th percentile (per SPC sounding
climatology). Locally these discrete cells ahead of the MCS are
producing as much as 1-2" of rainfall, while the squall line
itself is is only resulting in an inch or less (due to the
increase in forward speed as of late). This suggests that 3-hr
totals should generally range from only an inch or two across IA,
but localities that receive the most rainfall out ahead of the
line could see totals of 2-3". Given that much of the state has
already accumulated between 3-6" this week (300-600% of normal)
with NASA SPoRT-LIS 0-1m soil moisture anomalies at or above the
90th percentile, 3-hr FFGs generally range from only 1.5-2.0". As
a result, isolated to scattered instances of flash flooding will
be possible (and mostly confined to more sensitive areas that
receive 2"+ rainfall totals).

Churchill

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

ATTN...WFO...ARX...DMX...DVN...FSD...MPX...

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

LAT...LON   44489566 44399369 43629220 43259077 42569056
            41279120 40799242 40669397 40719484 41529483
            42419523 43089556 43559573