879
ACUS11 KWNS 272201
SWOMCD
SPC MCD 272201
MTZ000-272330-

Mesoscale Discussion 1450
NWS Storm Prediction Center Norman OK
0501 PM CDT Thu Jun 27 2024

Areas affected...Portions of southeastern Montana

Concerning...Severe Thunderstorm Watch 473...

Valid 272201Z - 272330Z

The severe weather threat for Severe Thunderstorm Watch 473
continues.

SUMMARY...The severe threat continues across Severe Thunderstorm
Watch 473. Severe wind gusts (a few of which could reach 75-90 mph)
are the main threat, though isolated instances of hail or even a
tornado remain possible.

DISCUSSION...Multicells and transient supercells are merging into a
singular MCS across portions of southeastern Montana. These storms
have been traversing a mixed boundary layer (characterized by 9.5
C/km 0-3 km lapse rates per 21Z mesoanalysis), with a history of
producing multiple severe gusts. Preceding the upscale growing MCS
is a warm sector that moistens with eastward extent, with 60s F
dewpoints beneath 7.5 C/km mid-level lapse rates contributing to
2000-3000 J/kg MLCAPE near the MT/ND border. Given widespread 50+ kt
effective bulk shear, the MCS should at least maintain intensity
through the evening. However, deep-layer shear vectors become more
perpendicular to MCS orientation with eastward extent, which may
promote further organization into a bow-echo MCS with increased
severe gust potential. A few 75-90 mph gusts may occur near the apex
of any bow echo that can form, with large hail possible with any
stronger storm cores. A tornado also cannot be ruled out with any
mesovortices that can become established.

..Squitieri.. 06/27/2024

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

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

LAT...LON   45050599 47040582 47670582 48050561 48050477 47730424
            47270422 45910436 45280439 45010473 45050599