South Dakota Mesoscale Discussion

Areas affected…southern/southeastern Montana…northeastern
Wyoming…and western South Dakota

Concerning…Tornado Watch 571…

Valid 112354Z – 120100Z

The severe weather threat for Tornado Watch 571 continues.

SUMMARY…The severe threat continues across WW 571.

DISCUSSION…Scattered thunderstorms continue across eastern
portions of WW 571. A small, forward-propagating complex continues
eastward across southwestern South Dakota, with more isolated
convection through the remainder of the western portions of the
state. Moderate to strong instability (2000-4000 J/kg MUCAPE)
continues within the pre-convective environment and deep shear
values have increased slightly due to modest increases in low- and
mid-level flow in this area. This environment will likely sustain
ongoing convection for the next several hours, and continued
forward-propagation of the southwestern South Dakota convective
cluster (250/35 storm motion) should eventually result in convection
extending beyond the current eastern bounds of WW 571 between
01-02Z. Spatial extensions of the watch across southern South
Dakota should be considered around or before that time.

Farther upstream, convection has been a bit slower to evolve across
Montana portions of WW 571, although new convection is approaching
the WW from the west (across central Montana) and from the southwest
with newer convection over far north-central Montana. The
approaching mid-level wave just west of the area will continue to
provide lift for additional convective development over the next
couple of hours, and shear/instability profiles will continue to
support large hail, damaging wind gusts, and a couple of tornadoes
through the evening. The severe threat continues across this
portion of WW 571 through at least 03Z.

..Cook.. 08/11/2019

…Please see for graphic product…


LAT…LON 46800916 46940803 46780435 45990235 44720205 43080198
42940311 43210413 43490504 43580593 43940614 44390702
44790886 44920950 45141003 45661017 46360981 46800916

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