425
ACUS11 KWNS 232359
SWOMCD
SPC MCD 232358
MTZ000-240230-

Mesoscale Discussion 1389
NWS Storm Prediction Center Norman OK
0658 PM CDT Sun Jun 23 2024

Areas affected...parts of northeastern Montana

Concerning...Severe potential...Watch possible

Valid 232358Z - 240230Z

Probability of Watch Issuance...40 percent

SUMMARY...Isolated supercell development appears possible near and
north of the Missouri River through 8-11 PM MDT.  It is not clear
that a severe weather watch will be needed due to localized nature
of the threat, but trends will continue to be monitored.

DISCUSSION...At least attempts at sustained deep convective
development appear underway west of Glasgow MT.  This appears near
the southern edge of the onset of mid-level height falls associated
with an upstream short wave trough progressing across the Canadian
and adjacent northern U.S. Rockies.  At lower levels this is focused
near/east of a weak surface low embedded within lee surface
troughing, aided by lift associated with low-level convergence and
warm advection.  Near the northern periphery of a plume of very warm
elevated mixed-layer air advecting northeast of the northern
Rockies, the approach of convective temperatures may also be a
contributing factor.

Based on various model output, this convective development may be
maintained into and through the 02-05Z time frame, though it may
remain isolated in nature to the south of the Saskatchewan border.
In the presence of strong deep-layer shear, beneath 50+ kt westerly
flow in the 500-300 mb layer, the environment is supportive of an
evolving supercell.  A hot and deeply mixed boundary-layer appears
characterized by CAPE in excess of 1000 J/kg, sufficient to support
a risk for large hail and locally severe wind gusts.

..Kerr/Gleason.. 06/23/2024

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

ATTN...WFO...GGW...

LAT...LON   48690409 48160442 47830699 47950747 48250737 48570708
            48820705 49050447 48690409