769
ACUS11 KWNS 101747
SWOMCD
SPC MCD 101746
SDZ000-NDZ000-NEZ000-MTZ000-WYZ000-101945-

Mesoscale Discussion 1226
NWS Storm Prediction Center Norman OK
1246 PM CDT Mon Jun 10 2024

Areas affected...Eastern Wyoming into western South Dakota

Concerning...Severe potential...Watch likely

Valid 101746Z - 101945Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorm development along a cold front is anticipated
within the next 1-2 hours across parts of the northern High Plains.
Initially discrete cells will pose a severe hail/wind, and perhaps a
tornado, risk before eventual upscale growth later this evening.
Watch issuance will likely be needed given favorable environmental
wind shear and improving buoyancy.

DISCUSSION...Recent GOES visible imagery and surface observations
show the eastward progression of a low to mid-level cold front
across the northern Rockies into the northern High Plains over the
past few hours. Thunderstorm development is expected along this
boundary as it impinges on the western fringe of returning low-level
moisture across WY/NE/SD (where dewpoints are climbing into the mid
to upper 50s). This somewhat high moisture content (dewpoints are
near the 90th percentile for the northern High Plains for early/mid
June) overlaid with 7-8 C/km mid-level lapse rates should support
MLCAPE near 2000 J/kg across the region by mid-afternoon as
thunderstorms develop and/or mature.

Deep-layer flow orthogonal to the front should support initially
discrete cells, including the potential for a few supercells, with
an attendant large hail (possibly up to 2 inches in diameter),
severe wind, and perhaps a brief tornado threat - especially across
northwestern SD where low-level winds are more south/southeasterly
ahead of a diffuse surface trough. Strong frontal forcing should
foster a gradual upscale growth into one or more semi-organized
clusters or lines with an attendant increase in the severe wind
potential. Watch issuance will be needed within the next hour or so
to address these concerns.

..Moore/Gleason.. 06/10/2024

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

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

LAT...LON   43310636 44370548 45280482 45750430 46180334 46210291
            45950242 45280220 44470221 43630251 42970296 42580354
            42330413 42180466 42190518 42370564 42500593 42810628
            42930635 43310636