Mesoscale Discussion 1358
NWS Storm Prediction Center Norman OK
0156 PM CDT Fri Jun 21 2024
Areas affected...Central and Eastern Wyoming...into far Southern
Montana
Concerning...Severe potential...Watch likely
Valid 211856Z - 212100Z
Probability of Watch Issuance...95 percent
SUMMARY...Weather watch issuance may be needed within the next
couple of hours as storm coverage increases over the high terrain of
W WY, with additional development happening further east along the
Laramie range in SE WY. Primary expected hazards are for damaging
winds and hail.
DISCUSSION...Thunderstorm coverage has increased over W WY beneath a
broad upper trough, with surface temperatures warming into the
mid-to-upper 70s F out ahead in Central WY. Dewpoints in the
mid-to-upper 50s F have spread northward along the front range of
the Rockies in Eastern WY as lee troughing beneath the upper wave
continues, with some dewpoints in the upper 40s to low 50s F
reaching into Central WY. This warm/moist boundary-layer air,
coupled with steep mid-level lapse rates of 8-9 C/km, has resulted
in SPC Mesoanalysis MLCAPE values of 1000-1500 J/kg. This buoyancy
is colocated with deep layer shear values in the 40-50 kt range,
indicating organized multicell clusters and supercells are possible.
As daytime heating and moisture transport continues out ahead of
developing convection, combinations of buoyancy and shear will
continue to support a supercell threat. Primarily straight-line
hodographs over W WY should support splitting supercells, and
coupled with abundant storm coverage, indicates the potential for
plentiful thunderstorm and outflow interactions that result in
primarily a damaging wind and hail threat. However, a brief tornado
cannot be ruled out in SE WY, where surface winds are locally backed
to the east. Additionally, RAP forecast profiles in NE WY show
potential for locally backed flow and curved hodographs later this
evening, though uncertainty in overall storm coverage and mode may
preclude a more robust tornado threat. Overall, the eastward extent
of severe hazards appears to be limited due to convective inhibition
increasing during the afternoon and evening, largely due to
subsidence behind a 500mb vort max exiting NE CO/SW NE.
Severe thunderstorm watch issuance is expected between 19-20Z,
primarily for 70 MPH winds and 2 inch hail.
..Halbert/Weinman/Hart.. 06/21/2024
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...BYZ...RIW...
LAT...LON 44550824 44840831 45220818 45450778 45450727 45480675
45450604 45410525 45270477 45010433 44650407 44370397
43930387 43500387 43130387 42610387 42160396 41730409
41520431 41290464 41150537 41250624 41650679 42220712
42730746 43030763 43350775 43740788 44140802 44550824