South Dakota Mesoscale Discussion

Areas affected…East-Central to Northeast NE…West-Central IA

Concerning…Heavy rainfall…Flash flooding possible

Valid 190630Z – 191230Z

SUMMARY…A persistent axis of heavy showers and thunderstorms
will continue to pose a flash flood threat over the next few

DISCUSSION…The latest satellite imagery is showing some
additional expansion of the cold convective tops impacting areas
of eastern NE and far western IA. The activity is focusing along
and just north of a quasi-stationary frontal zone where there is a
strong instability gradient in place. MUCAPE values over the
region are on the order of 2000 j/kg and there is an axis of 1.5
to 1.75 inch PWATs pooled along the boundary.

Some additional expansion and increase in the degree of convective
organization is possible over the next few hours as an upstream
shortwave impulse and associated upper-level jet streak impinges
on the region and fosters improving upper-level divergence.
Additionally, the convective threat will be facilitated by
favorable low-level speed convergence near the front and an
environment conducive for back-building cells which has already
been occurring locally over areas of Stanton, Cuming, and Wayne

The latest hires model suite has generally been under-performing
over the last few hours with the degree and scope of the
convective activity, and already there have been dual-pol radar
estimates of 3 to 4 inches. The latest HRRR guidance though
appears to be coming around to a somewhat better handling of the
event, and supports locally as much as an additional 3 to 4 inches
of rain for areas of especially northeast NE and along the border
with IA.

The additional rainfall will maintain the threat for flash
flooding over the next few hours, although the overall threat area
should tend to gain a bit more latitude as deeper layer southwest
flow arrives.


…Please see for graphic product…



LAT…LON 42599557 42319512 41949553 41759719 41789858
42209850 42559681

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