892
AWUS01 KWNH 210949
FFGMPD
WIZ000-MNZ000-IAZ000-211400-

Mesoscale Precipitation Discussion 0478
NWS Weather Prediction Center College Park MD
549 AM EDT Fri Jun 21 2024

Areas affected...Southern Minnesota...Northern Iowa...Western
Wisconsin...

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

Valid 210950Z - 211400Z

SUMMARY...Favorable training across above average soil
saturation/low FFG suggest flash flooding risk to expand eastward
through late morning as complex weakens

DISCUSSION...GOES-E 10.3um EIR loop shows overall convective
canopy continues to warm as it shifts across south central MN and
northern IA with a few narrower overshooting tops denoting smaller
areas of cloud top cooling to -50C. RADAR mosaic paints a similar
picture but fractured showers/thunderstorms still show strong warm
advection nature to the formation and continue to orient favorably
for training/repeat rainfall.  09z surface analysis notes the
surfac wave is currently in NW IA near SPW with warm front
extending eastward along the MN/IA state line before dropping
south across NE IA toward central IL.  Low level flow is weakening
at 5-10kts but still generally confluent with upper 60s to low 70s
Tds while near the boundary layer flow continues to veer more
southwest and slow from 20-25kts at 850mb. The LLJ still is
advecting modestly unstable air with MUCAPEs of 1000-1500 J/kg
continuing to rise downstream into W WI with recent hourly trends
of 100-200 J/kg noted.  Higher theta-E air through depth continues
to be at or just below 2" total PWat to allow for efficient
showers.  Though with the rate of flux reducing, very intense
rates are diminishing and starting to be between 1-1.5"/hr.

Still, deep layer steering will support east-northeast cell
motion, with southeast propagation vectors suggesting eastward
training/repeating to continue to the early morning.  As such,
spots of 2-3" are likely across southern MN and northern IA. NASA
SPoRT LIS 0-40cm soil saturation ratios are improving further east
into W WI, though central MN still are in upper 60 to 75% which
remains in the 90th percentile and FFG values remain about 1.5/hr
and about 2-2.25"/3hrs, especially over south-central MN where
they remain most saturated.  Given rainfall totals due to
training, flash flooding is considered possible as there will be
some spots exceeding these FFG values, though rates may be light
enough that flashy conditions may support slower rises and
inundation conditions especially in typically prone and urban
settings.

Gallina

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

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

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

LAT...LON   44719172 44469089 43939046 43339068 43039152
            42799317 42699443 42819552 43749525 44129471
            44389384 44659285