SPC MD 1484

MD 1484 CONCERNING SEVERE THUNDERSTORM WATCH 449... FOR PARTS OF SOUTHERN SOUTH DAKOTA/WESTERN NEBRASKA/NORTHEAST COLORADO/NORTHWEST KANSAS

Mesoscale Discussion 1484
NWS Storm Prediction Center Norman OK
0616 PM CDT Sat Aug 12 2017

Areas affected...Parts of southern South Dakota/western
Nebraska/northeast Colorado/northwest Kansas

Concerning...Severe Thunderstorm Watch 449...

Valid 122316Z - 130045Z

The severe weather threat for Severe Thunderstorm Watch 449
continues.

SUMMARY...Risk for severe hail and wind will continue in stronger
storms across the region well into the evening hours.  It currently
appears unlikely that another watch will be needed, but trends will
continue to be monitored.

DISCUSSION...Scattered strong to severe thunderstorm development is
well underway in the presence of moderately large CAPE and deep
layer shear near the lee surface trough across the high Plains. 
Despite the seasonably strong shear (largely due to pronounced
veering of winds with height,) westerly/northwesterly deep layer
mean flow appears rather modest, at or below 25 kt.  This is
resulting in generally slow storm motions, and little, if any,
east/southeastward advection of this unstable environment is
expected prior to the onset of nocturnal boundary layer cooling and
destabilization. So little change to the corridor of stronger storm
development is expected, but this environment probably will remain
conducive to the risk for storms capable of producing severe hail
and at least localized strong surface gusts well into the evening
hours.

..Kerr.. 08/12/2017

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

ATTN...WFO...FSD...ABR...GID...LBF...UNR...GLD...BOU...CYS...

LAT...LON   43529943 42849916 40859962 38840154 38810281 40130359
            41290371 42420365 43060313 43540252 43790169 43800046
            43529943 

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