Mesoscale Discussion 1369
NWS Storm Prediction Center Norman OK
0643 PM CDT Sun Jun 28 2026
Areas affected...parts of northwestern North Dakota
Concerning...Severe potential...Watch unlikely
Valid 282343Z - 290145Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated to widely scattered strong thunderstorm
development with potential to produce large hail and localized
strong downbursts is possible into the 7-9 PM CDT time frame, before
rapidly weakening.
DISCUSSION...In the wake of one notable mid-level short wave trough,
pivoting north-northwestward across Saskatchewan/Manitoba, around
the northeastern periphery of an occluded cyclone centered over far
southeastern Alberta, mid/upper support for convective development
across the region is weak. Low-level flow is also weak within
broad weak lingering surface troughing centered over the western
Dakotas, but convergence has become strong enough in locations to
contribute to the initiation of isolated thunderstorms.
Boundary-layer destabilization has maximized, and mid-level
inhibition associated with a plume of warm elevated mixed-layer air
has been suppressed southeastward.
Despite the weak low-level flow and shear, deep-layer shear beneath
40-50 kt southwesterly 500 mb flow is strong and supportive of
supercells with potential to produce large hail, as likely was the
case with one initial storm which evolved across the international
border to the east-northeast of Williston earlier. It is possible
ongoing convection may persist and intensify further the next couple
of hours, particularly the cell developing to the south-southwest of
Bismarck, which appears likely to have the most prolonged access to
updraft inflow of moist air characterized by CAPE on the order of
3000 J/kg. However, with the onset diurnal cooling and increasing
inhibition for boundary-layer parcels, weakening and dissipation of
storms may be rapid.
..Kerr/Thompson.. 06/28/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FGF...ABR...BIS...
LAT...LON 48920251 49060203 48849924 48479885 47669903 46460049
45900148 46320191 47210140 47470187 48250278 48920251
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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