SPC MD 1262

MD 1262 CONCERNING SEVERE THUNDERSTORM WATCH 450... FOR EASTERN WYOMING...WESTERN SOUTH DAKOTA...AND WESTERN NEBRASKA

Mesoscale Discussion 1262
NWS Storm Prediction Center Norman OK
0701 PM CDT Wed Jun 26 2019

Areas affected...Eastern Wyoming...western South Dakota... and
western Nebraska

Concerning...Severe Thunderstorm Watch 450...

Valid 270001Z - 270200Z

The severe weather threat for Severe Thunderstorm Watch 450
continues.

SUMMARY...Rapid thunderstorm intensification and upscale growth
appears possible through 7-9 PM MDT.  Strongest storms pose a risk
for large to very large hail, and perhaps some risk for a tornado,
before the risk for damaging wind gusts becomes more prominent.

DISCUSSION...Convective development which initiated near/northeast
of the Laramie Mountains is now east of the Interstate 25 corridor,
and continues to spread northeastward and eastward into the adjacent
High Plains.  This appears to be occurring just ahead of a weak
mid-level trough axis, within 15-20 kt west-southwesterly deep layer
mean ambient flow.

Due to pronounced veering of wind fields with height, deep-layer
shear is sufficiently strong for organized severe convection,
including supercells, however.  And, objective analysis indicates
that the environment across the Sand Hills of Nebraska into the
Badlands of South Dakota has become characterized by strong
instability.  This includes CAPE in excess of 4000 J/kg, in the
presence of steep lapse rates.

As storms spread into this environment through 01-03Z, rapid
thunderstorm intensification appears possible, with considerable
further upscale convective growth in the presence of strengthening
southerly 850 mb flow to 30 kt.  This may be most pronounced near
the Nebraska/South Dakota border area, near/northwest of Chadron,
through the Badlands, where inhibition associated with very warm
elevated mixed-layer air appears weakest.

..Kerr.. 06/27/2019

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

ATTN...WFO...LBF...UNR...CYS...

LAT...LON   43440451 43820429 44360207 41950207 41410259 41500351
            42440380 42920450 43440451 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1262.html