ACUS11 KWNS 201854
SWOMCD
SPC MCD 201853=20
SDZ000-MTZ000-WYZ000-202030-

Mesoscale Discussion 1175
NWS Storm Prediction Center Norman OK
0153 PM CDT Tue Jun 20 2023

Areas affected...portions of northeast Wyoming into extreme
southeast Montana

Concerning...Severe potential...Watch possible=20

Valid 201853Z - 202030Z

Probability of Watch Issuance...40 percent

SUMMARY...The severe threat is increasing across portions of the
northern High Plains. Severe wind and hail are expected to be the
primary hazards with the stronger storms. A Severe Thunderstorm
Watch issuance may be needed to address the pending threat.

DISCUSSION...The combination of orographic lift, diurnal heating,
and deep-layer ascent from a mid-level trough approaching from the
west, are all contributing to an increase in anafrontal thunderstorm development. These storms are developing amid increasing mid-level
flow, with strengthening southwesterly flow above 700 mb
contributing to 50+ kts of effective bulk (speed) shear. With the
RIW VAD and RAP forecast soundings both depicting relatively
straight, elongated hodographs, transient supercells and short line
(possible bowing) segments are the expected storm modes. Though
overall buoyancy is modest, the presence of 7-8 C/km mid-level lapse
rates suggests that large hail may accompany the stronger storm
cores. Downward momentum transport of the stronger flow aloft in
higher-terrain areas may also support severe gusts. A Severe
Thunderstorm Watch issuance may be needed pending greater storm
coverage, most likely once storms progress east and north of the Big
Horn Mountains.

..Squitieri/Hart.. 06/20/2023

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-l-ovfe_uspLvu6u5o0DAOWlhrcyA29LfwC785s1ezswp9unVlYSjuA6qSO5-cCq7pYZZMz7k= 0bDO_PDV7KA9sl7bAA$ for graphic product...

ATTN...WFO...UNR...CYS...BYZ...RIW...

LAT...LON 45060382 44230398 43350518 42800649 42610734 42710787
43420798 43570785 44790635 45380536 45540439 45060382=20


=3D =3D =3D
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