Subj : MESO: Heavy rain - floodi
To   : All
From : Mike Powell
Date : Fri Jun 09 2023 18:52:00

AWUS01 KWNH 092307
FFGMPD
KSZ000-NEZ000-100405-

Mesoscale Precipitation Discussion 0452
NWS Weather Prediction Center College Park MD
706 PM EDT Fri Jun 09 2023

Areas affected...south-central Nebraska, northern/central Kansas

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

Valid 092305Z - 100405Z

Summary...Slow-moving, heavy downpours are producing localized
areas of 2-2.5 inch/hr rain rates across portions of the
discussion area.  These trends should continue through at least
02Z or so.

Discussion...Scattered thunderstorms have congealed into a couple
of very slow-moving mesoscale convective complexes - one located
across south-central Nebraska just northwest of Grand
Island/Kearney and another just south of I-70 west of Hill City. 
Steering flow aloft has been weak most of the day, allowing for
motion of the storms to be governed by local convective processes
and cold pool propagation.  Additionally, a very warm/unstable
airmass continues to reside ahead of the storms, with 1500-2000
J/kg MLCAPE supporting robust updrafts especially near the leading
edge of the cold pools.  Slow movement has also resulted in areas
of 2-2.5 inch/hr rain rates that have locally exceeded FFG
thresholds (generally in the 1.5-2.5 inch/hr range across the
area).  Moderate MRMS Flash responses have also occurred in a few
spots.

The overall lack of synoptic forcing/upper support for the storms
casts some doubt on their longevity through the evening. 
Additionally, the lack of low-level shear could also play a role
in weak organization of the storms as 850mb flow should only
increase into the 20-25 kt range across far western Kansas through
the early evening.  Current thinking is that ongoing cells will
continue to slowly/erratically propagate and produce local 2+
inch/hr rain rates through at least 02Z, with a few areas of flash
flood potential emerging as a result.  Gradual weakening of
convection is probable as nocturnal boundary layer cooling occurs
after 02Z or so.  The degree of weakening should also depend on
local convective organization, with the best chance for a
longer-lived MCS existing across western Kansas later tonight.

Cook

ATTN...WFO...DDC...GID...GLD...ICT...LBF...OAX...TOP...

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

LAT...LON   41749802 40959688 39709662 38329682 37869819 
            37620168 38390201 39390196 39650111 40190031 
            40600010 41589926 

= = =
--- SBBSecho 3.14-Linux
 * Origin: Ilink: CCO - capitolcityonline.net (454:1/105)

.