MD 1286 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF NORTHERN WYOMING…FAR SOUTHEASTERN MONTANA…FAR WESTERN SOUTH DAKOTA
Mesoscale Discussion 1286
NWS Storm Prediction Center Norman OK
0324 PM CDT Mon Jun 26 2023
Areas affected...portions of northern Wyoming...far southeastern
Montana...far western South Dakota
Concerning...Severe potential...Watch possible
Valid 262024Z - 262300Z
Probability of Watch Issuance...60 percent
SUMMARY...The severe threat is increasing across portions of the
northern High Plains. A few supercells may develop, supporting a
risk for large hail (including an instance or two of 2+ inch
stones), as well as a couple of severe gusts. Convective trends are
being monitored for the need of a Severe Thunderstorm Watch issuance
later this afternoon.
DISCUSSION...MRMS mosaic radar imagery and satellite data suggests
that convection is gradually deepening along the higher terrain of
the Rockies. Though convection has yet to move off of the higher
terrain, stronger forcing should begin to overspread the northern
High Plains in the next few hours in association with an approaching
500 mb vort max over northwestern UT. While low-level moisture is
not overly rich, 8+ C/km lapse rates from the surface to 500 mb is
supporting 2000+ J/kg SBCAPE/MUCAPE, which is adequate for supercell
development given the presence of 40+ kt effective bulk shear values
(driven by straight, long hodographs). The deep-layer speed shear
may support sufficient enough hail growth for stones to exceed 1
inches in diameter, with a couple of 2+ inch diameter stones
possible. A few severe gusts may also occur with the heavier
supercell precipitation cores given the steep low-level lapse rates.
It is unclear exactly when a significant uptick in convective
intensity and relatively robust supercell development will occur. It
is possible that such development may not occur for at least a few
more hours. Nonetheless, Severe Thunderstorm Watch issuance will
likely be needed at some point this afternoon or evening and
convective trends are being monitored closely for more precise
timing of the watch issuance.
..Squitieri/Grams.. 06/26/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...UNR...CYS...BYZ...RIW...
LAT...LON 43391037 44540896 45490731 45640592 45640456 45070351
44510309 44180317 43120370 42680452 42390547 42400736
42570816 43391037
