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Mesoscale Discussion 1233
NWS Storm Prediction Center Norman OK
0149 PM CDT Mon Jun 20 2022

Areas affected...Southeast ND...northeast SD...and parts of
northwest MN

Concerning...Severe potential...Watch likely 

Valid 201849Z - 202115Z

Probability of Watch Issuance...95 percent

SUMMARY...The severe-storm threat will increase across parts of the
northern Plains and Red River Valley between 20-22Z. Large to very
large hail, severe gusts (some significant) and a tornado or two
will be possible. A watch will be needed this afternoon.

DISCUSSION...Surface observations and MVX radar data depicts a
northeast/southwest-oriented quasi-stationary surface boundary
extending across the Red River Valley. Ongoing elevated convection
and related cloud debris north of the boundary across northeast ND
will continue to reinforce the baroclinic zone, while strong diurnal
heating of an increasingly moist boundary layer (upper 60s/lower 70s
dewpoints) continues along and south of the boundary. As a subtle
midlevel impulse evident in water vapor imagery over the western
Dakotas overspreads the boundary this afternoon, current thinking is
that convection will develop in the 20-22Z time frame.

Regional VWP data shows strong midlevel southwesterly flow
approaching the area, which will contribute to 45-55 kt of effective
shear amid moderate to strong surface-based buoyancy and steep
midlevel lapse rates. While these factors will support organized
convection (including initially semi-discrete supercells) along and
south of the boundary, largely front-parallel deep-layer flow/shear
coupled with the strengthening large-scale ascent could yield
congealing cold pools and upscale growth. Large to very large hail
and severe gusts will be possible with any supercell structures, and
a tornado or two cannot be ruled out owing to modest low-level
hodograph curvature. With time, convective clustering amid steep
low/midlevel lapse rates could support organized bowing
segments/supercell clusters capable of severe gusts (some of which
could be significant). A watch will be needed for parts of the area
this afternoon.

..Weinman/Grams.. 06/20/2022

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

ATTN...WFO...FGF...ABR...BIS...

LAT...LON   46169946 46769842 47729770 48339738 48569648 48389559
            47709511 46739511 45819644 45189793 45119907 45629957
            46169946