SPC MD 1428



MD 1428 CONCERNING SEVERE THUNDERSTORM WATCH 421… FOR SOUTHERN SD…WESTERN INTO CENTRAL NE

MD 1428 Image


Mesoscale Discussion 1428
NWS Storm Prediction Center Norman OK
0858 PM CDT Sat Aug 08 2020

Areas affected...Southern SD...Western into central NE

Concerning...Severe Thunderstorm Watch 421...

Valid 090158Z - 090330Z

The severe weather threat for Severe Thunderstorm Watch 421
continues.

SUMMARY...The severe wind/hail threat continues in and near WW 421
this evening. The primary threat may transition to more of a
damaging wind risk later tonight, focused across north-central NE
into south-central SD. Downstream watch issuance may be required
later tonight.

DISCUSSION...Multiple thunderstorm clusters have produced severe
wind and hail in and near WW 421 since 23Z. Isolated reports of very
large hail were reported earlier across western SD/NE, and measured
severe wind gusts (including 72 kt at Chadron, NE) have been noted
across northwest NE in association with a small bowing segment. The
strongest convection as of 0145Z is ongoing across southwest SD into
northwest NE. 

The evolution of convection this evening remains somewhat uncertain.
Very steep midlevel lapse rates and strong buoyancy noted in 00Z
soundings from UNR and LBF will continue to support a conditional
risk of severe wind with any organized convection that persists, and
a conditional hail risk with any discrete cells that can be
maintained. The low-amplitude shortwave trough that helped to
initiate storms will continue to move across SD/NE, which should
help to maintain convection into late tonight. The reasonably strong
cold pool noted across northwest NE/southwest SD will likely
continue to support a modestly organized MCS into the late evening
across south-central SD/north-central NE, with a continued threat of
severe wind gusts. A concentrated corridor of potentially damaging
wind will be possible as this occurs, though increasing MLCINH and
only a modest low-level jet response may temper the threat to some
extent. 

Downstream watch issuance may be required later tonight to address
the severe wind threat spreading into a larger portion of southern
and eastern SD into northern NE.

..Dean/Dial.. 08/09/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FSD...OAX...ABR...GID...LBF...UNR...GLD...

LAT...LON   40110138 41020187 41610213 42110240 43340268 43810279
            44070261 44230249 44320216 44420180 44560021 43639872
            42749813 41839849 40899939 40210007 40110138 

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