Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jun 24 2023 03:32:03

AWUS01 KWNH 240332
FFGMPD
IAZ000-NEZ000-SDZ000-240929-

Mesoscale Precipitation Discussion 0574
NWS Weather Prediction Center College Park MD
1131 PM EDT Fri Jun 23 2023

Areas affected...much of South Dakota

Concerning...Heavy rainfall...Flash flooding likely

Valid 240329Z - 240929Z

Summary...An advancing cluster of convection across western
portions of South Dakota should result in at least isolated flash
flood potential across the discussion area through 09Z.

Discussion...Convection initially over eastern Wyoming has evolved
into a forward-propagating linear complex extending from near Y22
to near RAP.  Ahead of this complex, scattered to numerous
thunderstorms have deepened generally along and north of a nearly
stationary surface boundary extending from near RAP to just south
of ABR.  Low-level convergence was focused near the surface
boundary, which was collocated with the nose of 20-30 kt 850mb
flow.  Strong instability (1500 J/kg MLCAPE) and high moisture
content (1.5 inch+ PW) was allowing for efficient rainfall
production beneath the storms, while the combination of relatively
slow storm motions (around 10-20 knots) and occasional cell
mergers were allowing for occasional 2-3 inch/hr rain rates to
develop.  These rates were exceeding the local FFG thresholds
(generally around 1-1.5 inch/hr) at times, prompting moderate MRMS
Flash responses.

Ongoing convective trends should continue, but gradually translate
eastward over time in tandem with both the 1) eastward translation
of the low-level jet across Nebraska and 2) eastward progression
of the linear MCS currently across western South Dakota.  FFG
thresholds will continue to be exceeded occasionally, resulting in
areas of excessive runoff.  Given forcing and lingering
instability, storms should not lose much intensity overnight
despite gradual boundary layer cooling.  These storms should reach
eastern South Dakota (from ABR southward to MHE) during the 06-09Z
timeframe.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!84TKC7lmfUHUncg1SFlYqxgO3XJvabxesO_olHUj0ziKSnHn45XNgW4nNeXK3a3ZOqkr=
GjWpM-iQ1e7LOrSXWid1jTc$  for graphic product...

ATTN...WFO...ABR...FSD...LBF...UNR...

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

LAT...LON   45760049 45619868 45259730 44219653 43229651=20
            42909728 42889898 43250128 43790276 45000270=20
            45380238 45640165=20

=3D =3D =3D
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