Mesoscale Discussion 1348
NWS Storm Prediction Center Norman OK
1240 PM CDT Sat Jun 27 2026
Areas affected...eastern Montana and northeast Wyoming
Concerning...Severe potential...Watch likely
Valid 271740Z - 272015Z
Probability of Watch Issuance...95 percent
SUMMARY...Severe storms are expected to develop by 19-20Z with an
associated risk for wind gusts of 80+ mph, large to very large hail
of 2+ inches, and perhaps a tornado or two. A watch is likely.
DISCUSSION...Latest mesoanalysis placed a surface low over far
southeast MT or northeast WY with an associated stationary front or
trough stretching from northwest ND to the vicinity of the Big Horn
Mountains in north-central WY. A corridor of higher boundary-layer
moisture content resides along and to the north of the front, which
coincides with the northern edge of an EML plume, supporting MLCAPE
of 1000-1500 J/kg, per latest objective analysis. Daytime heating
and increasing height falls/forcing for ascent are expected to
support further air mass destabilization by early to mid afternoon,
while a capping inversion for surface-based parcels becomes
progressively weaker.
Latest short-term model guidance indicates an increased likelihood
of surface-based thunderstorm development by 19-20Z along the Big
Horn Mountains. That notion is corroborated by the deepening cumulus
field along that terrain feature, per recent visible satellite
trends. RAP-based forecast soundings in that area indicate 40-50 kt
of north-northeast deep-layer shear supportive of supercells as the
initial storm mode with the primary hazard being large to very large
hail. While low-level shear isn't forecast to be particularly
strong, the presence of the front may serve as a local vorticity
source for some tornado threat. By late afternoon into early
evening, there is good model agreement in storms coalescing into a
broader-scale, bowing structure capable of swaths of damaging winds,
including gusts of 80+ mph.
..Mead/Guyer.. 06/27/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...BYZ...GGW...RIW...
LAT...LON 44850544 44650596 44430686 44790821 45260856 46460754
47520711 47920690 48380577 48090460 47800451 46950419
46080435 45130465 44850544
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...75-90 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN
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