SPC MD 1428

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