MD 0904 CONCERNING SEVERE THUNDERSTORM WATCH 227… FOR CENTRAL AND SOUTHEAST SOUTH DAKOTA
Mesoscale Discussion 0904 NWS Storm Prediction Center Norman OK 0418 AM CDT Wed Jun 27 2018 Areas affected...central and southeast South Dakota Concerning...Severe Thunderstorm Watch 227... Valid 270918Z - 271045Z The severe weather threat for Severe Thunderstorm Watch 227 continues. SUMMARY...Intense thunderstorm cluster is currently moving through central South Dakota with a history of producing very large hail. This storm should continue through the early morning and move out of WW227 later this morning. This will likely require a new watch across portions of southeast South Dakota. DISCUSSION...Intense thunderstorm cluster centered over Hughes County is moving continues to move southeast along the periphery of the higher instability axis. Although cloud tops appear to have stopped cooling, MESH imagery suggests the thunderstorm cluster has been capable of producing hail hail in excess of 2.5" for much of the last few hours. This radar-derived hail-size estimate was corroborated by a 2.5" hail report around 730Z. The environment ahead of this thunderstorm remains conducive for thunderstorm maintenance. Deep-layer shear remains at or above 50 knots and most-unstable CAPE along and ahead of the storm is at or above 2000 J/kg. Given persistent warm-air advection ahead of the storm, the ongoing organization of the thunderstorm cluster, and a favorable thermodynamic and kinematic environment, expectation is that the storm will move out of WW227 in the next 1-2 hours. A new watch downstream of WW227 appears likely warranted. ..Marsh.. 06/27/2018 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FSD...ABR...UNR... LAT...LON 44260099 45099977 43779710 43089836 44260099
from SPC Mesoscale Discussions http://bit.ly/2Km0Bvj
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