SPC MD 1742

MD 1742 CONCERNING SEVERE THUNDERSTORM WATCH 500... FOR THE EAST CENTRAL AND NORTHERN PLAINS INTO THE UPPER MIDWEST

Mesoscale Discussion 1742
NWS Storm Prediction Center Norman OK
0650 PM CDT Sun Oct 11 2020

Areas affected...the east central and northern Plains into the upper
Midwest

Concerning...Severe Thunderstorm Watch 500...

Valid 112350Z - 120145Z

The severe weather threat for Severe Thunderstorm Watch 500
continues.

SUMMARY...The threat for severe wind and hail will continue across
WW 500 for the next 1-2 hours, especially across southeast South
Dakota, eastern Nebraska, and adjacent areas of Iowa and Minnesota.
A transition to primarily a wind threat is expected heading into the
late evening.

DISCUSSION...Thunderstorm coverage continues to increase from
northwest MN southward into eastern NE as an east/southeast surging
cold front begins to overtake the leading surface trough that has
acted as the focus for initial convection. Deep layer flow
orientated along this boundary has lead to largely broken line
segments and transient discrete modes across the eastern Dakotas and
west/southwest MN. Storm interactions and a narrow axis of
instability has largely limited the severe potential thus far, and
will likely continue to do so into the late evening hours. However,
a brief severe wind, and perhaps severe hail, threat will remain
possible with any stronger convection that can remain organized as
storms moves into central MN where effective bulk shear is slightly
stronger due to backed low-level flow in the vicinity of a diffuse
surface warm front.

Further south into the SD/NE/IA/MN region, a stronger zonal
component to upper-level winds has allowed for more persistent
discrete modes. Effective bulk shear values on the order of 30-40
knots will continue to favor supercellular characteristics and
support the potential for severe hail and strong winds in the near
term. Eventual upscale growth into linear modes (and an associated
increase in severe wind potential) is still expected as the cold
front catches up with the primary convective line through the
evening.

..Moore/Dial.. 10/11/2020

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

ATTN...WFO...MPX...DMX...FGF...FSD...OAX...ABR...GID...

LAT...LON   46239670 46549611 46359541 45309477 44469478 43149499
            41929540 41249584 41029672 40979727 41059772 41299779
            41959748 42919708 43649691 44229682 45069677 46239670 

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