483
ACUS11 KWNS 121933
SWOMCD
SPC MCD 121933
WIZ000-MNZ000-NDZ000-122130-

Mesoscale Discussion 1238
NWS Storm Prediction Center Norman OK
0233 PM CDT Wed Jun 12 2024

Areas affected...Central to northern Minnesota

Concerning...Severe potential...Watch likely

Valid 121933Z - 122130Z

Probability of Watch Issuance...80 percent

SUMMARY...Thunderstorm development is expected across eastern North
Dakota and northwestern Minnesota in the coming hours. Initially
weak cells will intensify to severe limits as they migrate into
central and eastern Minnesota. Watch issuance is anticipated to
address this concern.

DISCUSSION...Recent GOES imagery shows growing cumulus with a few
deepening mid-level towers (some with occasional lightning) in the
vicinity of a surface low near Grand Forks, ND east/northeastward
along a warm front into northern MN. This is likely an indication of
increasing ascent ahead of the approaching mid-level shortwave (such
ascent is even more evident upstream across northern MT into
southern Saskatchewan) as well as gradual destabilization of the
warm sector as dewpoints continue to rise into the low 60s. Recent
RAP mesoanalyses also suggest that MLCIN is beginning to erode
across central to northern MN. Combined with the aforementioned
satellite trends, this suggests that convective initiation appears
most probable across north/northwestern MN in the coming hours.

Thunderstorms initiating in this zone will be on the northwestern
fringe of the MLCAPE axis. Additionally, the KMVX VWP is currently
sampling somewhat poor low-level shear given its proximity to the
surface low; however, low-level helicity appears to be stronger
(around 150 m2/s2 0-1 km SRH) downstream to the east of a weak
surface confluence axis based on VWP observations from KDLH.
Deep-layer shear is also expected to improve through the late
afternoon/evening hours with the approach of the mid-level jet.
Consequently, storms are expected to intensify as they migrate to
the east/southeast towards eastern/northeastern MN. Initially
discrete to semi-discrete cells will likely evolve into organized
supercells with an attendant risk for severe winds, large hail
(possibly up to 3 inches in diameter) and tornadoes (though the
tornado threat may be conditional on establishing one or more
dominant right-moving supercells across northeast MN, which may be
difficult given nearly straight hodographs above 1 km). Watch
issuance is expected in the next 1-2 hours to address this concern
as initiation becomes more imminent.

..Moore/Goss.. 06/12/2024

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

ATTN...WFO...DLH...MPX...FGF...

LAT...LON   45409294 45209337 45209394 45369453 46309655 46489680
            46859689 47569648 48279618 48679576 48599291 48239208
            47689181 47069183 46599197 46289212 45409294