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000
AWUS01 KWNH 161421
FFGMPD
MOZ000-MNZ000-IAZ000-KSZ000-NEZ000-SDZ000-161800-

Mesoscale Precipitation Discussion 0158
NWS Weather Prediction Center College Park MD
1021 AM EDT Tue Apr 16 2024

Areas affected...eastern Nebraska, southeastern South Dakota,
northeastern Kansas, northwestern Missouri, and western into
central Iowa

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

Valid 161420Z - 161800Z

Summary...Bands of convection are resulting in prolonged rain
rates (including 2+ inch/hr rates at times) across the discussion
area.  Areas/spots of flash flooding are possible through 18Z this
morning.

Discussion...Over the last hour or so, a couple of dominant
convective bands have taken on a favorable orientation for
training despite relatively fast steering flow and storm motions.
One of these bands extended from near Yankton, SD to near
Columbus, NE, with rightward-moving structured embedded and
assisting in both 1 inch/hr rain rates and 2-2.5 inch/3-hr rain
rates beneath the band.  This area was continuing to ingest
surface-based parcels due to southeasterly low-level flow and near
60F dewpoints beneath very cold air aloft (-20C at 500mb),
contributing to relatively efficient rain rates.  Local FFGs in
the 1.5 inch/hr range were being approached on a localized basis,
suggesting a continued flash flood risk as long as convection
remains rooted near the surface.  Some cells were moving northward
toward cooler surface air, however, which may weaken storms and
lower rain rates as they drift into southeastern South Dakota.

Southeast of this area, a second band of more robust convection
extended from near Clarinda in southwest Iowa through Topeka, KS.
These cells are also training and fostering areas of nearly 2
inch/hr rain rates due to favorable orientation to south-southwest
steering flow aloft.  Stronger buoyancy in this area was also
contributing to slightly stronger/deeper updrafts per satellite
imagery.  These storms were also lifting northward toward a
low-level boundary and stable air across central Iowa, although
ascent/forcing aloft may sustain training cells toward the Des
Moines, IA area after 16Z or so.

Models suggest that warm advection/destabilization will develop
northward into areas of central/northwestern Iowa over time,
resulting in a broader spatial opportunity for deep, training
updrafts and heavy rain rates.  Areas of 1-2 inch/hr rain rates
are expected to approach FFG thresholds over the discussion area
on at least a spotty basis through 18Z or so.  The threat could
persist beyond 18Z, although model trends seem to indicate a
faster forward progression of convection (and less training)
through the afternoon hours.  This scenario will be re-evaluated
for another potential MPD after 18Z.

Cook

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

ATTN...WFO...DMX...EAX...FSD...ICT...MPX...OAX...SGF...TOP...

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

LAT...LON   44399753 44339634 43329360 41849265 39539264
            38389370 38069443 38039543 39329568 40479675
            42379784 43669793