SPC MD 1147

MD 1147 CONCERNING SEVERE THUNDERSTORM WATCH 344... FOR NORTHEAST SOUTH DAKOTA INTO CENTRAL MINNESOTA.

Mesoscale Discussion 1147
NWS Storm Prediction Center Norman OK
0758 PM CDT Wed Jul 08 2020

Areas affected...northeast South Dakota into central Minnesota.

Concerning...Severe Thunderstorm Watch 344...

Valid 090058Z - 090300Z

The severe weather threat for Severe Thunderstorm Watch 344
continues.

SUMMARY...The threat for severe weather continues across WW 344.
Thunderstorm development should become more likely across northeast
South Dakota over the next 1-2 hours, while the tornado threat
should decrease across central Minnesota.

DISCUSSION...A couple more tornado reports have been noted across
central MN in association with a few supercells that were able to
become rooted along the warm front draped across the region.
However, recent radar trends over the past half hour have shown
increasing storm interactions due to a considerable along-boundary
component to the deep layer shear. This upscale growth trend should
continue over the next hour and will act to gradually diminish the
tornado threat, though a brief tornado or two remain possible with
any new developing updrafts along the warm frontal boundary in the
near term. Although gradual upscale growth is expected, the
environment remains supportive of organized convection and the
potential for severe hail and wind. 

To the southwest, GOES visible imagery has shown at least a couple
attempts at convective initiation along a stationary
boundary/surface trough. Although these attempts have not yielded
sustained convection (likely due to lingering inhibition across this
region), this suggests that CI remains possible over the next couple
of hours. Given strong instability (4000-4500 J/kg MLCAPE) and 50-55
knots of effective bulk wind shear over this region, any convection
that can become sustained will pose the potential for severe hail
and wind. Additionally, high ambient low-level vorticity along the
boundary coincident with 100-200 J/kg of 0-3 km MUCAPE suggests that
a brief landspout or two is possible.

..Moore.. 07/09/2020

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

ATTN...WFO...DLH...MPX...FGF...FSD...ABR...

LAT...LON   45939685 46439625 47469488 47899331 47469169 46639122
            45799136 45729296 45519483 45249613 44749676 44439733
            44539760 45069756 45659715 45939685 

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1147.html