South Dakota Mesoscale Discussion

Areas affected…Eastern WY…Far Western SD…Western NE Panhandle

Concerning…Severe potential…Watch likely

Valid 101851Z – 102045Z

Probability of Watch Issuance…80 percent

SUMMARY…Increasing thunderstorm coverage is anticipated this
afternoon, with some supercells likely. Very large hail, strong wind
gusts, and a tornado or two possible.

DISCUSSION…Thunderstorm coverage is expected to increase this
afternoon as forcing for ascent attendant to an approaching
shortwave trough interacts with a diurnally destabilizing boundary
layer. Destabilization across much of the region will be driven
primarily by increasing surface temperatures and boundary-layer
mixing, but some modest moisture advection is anticipated as well.
Strong moisture advection is possible across southeast WY and the
western NE Panhandle. Recent surface analysis reveals the dewpoint
has increased 4 to 6 degrees F over the past 3 hours as the warm
front moves northward.

Attempts at sustained deep convection across the region have failed
thus far, likely due to minimal buoyancy. However, continued
attempts are anticipated, with more sustained/organized updrafts
expected. Given the supercell wind profile in place, discrete
supercells are possible. Primary threat with these discrete storms
would be very large hail, although strong wind gusts and a tornado
or two are also possible. Upscale growth/linear transition is then
anticipated later this evening.

..Mosier/Hart.. 09/10/2019

…Please see for graphic product…


LAT…LON 42880635 44340650 44800563 44390399 41850323 41030364
41030534 42880635

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