ACUS11 KWNS 272247
SWOMCD
SPC MCD 272247=20
SDZ000-NDZ000-280045-

Mesoscale Discussion 1355
NWS Storm Prediction Center Norman OK
0547 PM CDT Sat Jun 27 2026

Areas affected...parts of the western Dakotas

Concerning...Tornado Watch 406...

Valid 272247Z - 280045Z

The severe weather threat for Tornado Watch 406 continues.

SUMMARY...The risk for supercells capable of producing sizable hail
and increasing potential for a couple strong tornadoes is probably
highest between now and 6-7 PM MDT.

DISCUSSION...Strong thunderstorm development is now well underway
within clusters developing north and northeast of the Big Horn
Mountains, and within deep surface troughing, near the northeastern
Montana international border. More recent, and still discrete,
storm initiation has been occurring in the vicinity of the surface
trough axis near the southeastern Montana/Dakotas state border
through western South Dakota to the north of the Black Hills.=20
Immediately to the north and east of the latter activity,
boundary-layer instability is currently maximized in a narrow
corridor and appears to include CAPE in excess of 3000 J/kg.=20

Prior to the arrival of consolidating and strengthening outflow
emanating from the upstream convection, there appears a couple of
hour window for intensifying discrete storm development, in the
presence of strong deep-layer shear beneath 40-50 kt southerly flow
around 500 mb. Some further strengthening of south-southeasterly
flow around 850 mb through 00-01Z may contribute to enlarging
clockwise-curved low-level hodographs increasingly conducive to the
development of tornadoes, in addition to large hail and localized
strong downbursts.

..Kerr.. 06/27/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-kzXQc9F4gkkwBv_KQLilrnVjhKOIlyacF2xzGMdS5gnwplrCJSX6I267Agr6Vk5qdjv3LkPS= AsAidE36fZ9OQ_4A40$ for graphic product...

ATTN...WFO...ABR...BIS...UNR...

LAT...LON 45840350 46200350 46740357 47460386 47720339 47360277
46960220 46110128 44810162 44490194 44650237 45410301
45840350=20

MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH
MOST PROBABLE PEAK WIND GUST...75-90 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN


=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: Capitol City Weather Station (1:2320/127)