South Dakota Mesoscale Discussion

Areas affected…Portions of north Dakota and north central South

Concerning…Severe potential…Watch likely

Valid 061927Z – 062100Z

Probability of Watch Issuance…95 percent

SUMMARY…Additional severe thunderstorm development is expected in
the next 1 to 2 hours. A watch is likely.

DISCUSSION…A line of elevated convection has been ongoing in
southwest North Dakota for most of the morning and early afternoon.
North of this activity, new surface based development has begun
along the cold front in Dunn county, North Dakota. Dewpoints have
not mixed out as much as RAP forecasts suggest with upper 50 to low
60 dewpoints remaining across southwest North Dakota with
temperatures in the low 90s. This has yielded MLCAPE in this area
around 1500 J/kg with some increase to near 2000 J/kg expected as
temperatures increase a few more degrees. The BIS VWP shows greater
than 50 knots of northwesterly flow at 4-5 km which is 5 to 10 knots
stronger than RAP forecast soundings across the region. This
combination of instability and shear will support supercells as the
primary storm mode. Given the favorable CAPE/shear space and steep
mid-level lapse rates around 8.5 C/km, large hail, some very large,
will be the primary threat initially before storms eventually grow
upscale into a forward propagating MCS. The primary corridor with
the highest threat for wind damage will be from near Bismark to
areas slightly west of Aberdeen.

..Bentley.. 08/06/2019

…Please see for graphic product…


LAT…LON 45960274 46350297 47450309 48030239 48450086 47339964
45109884 44439928 44280004 44620099 45230158 45530220

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