Mesoscale Discussion 1385
NWS Storm Prediction Center Norman OK
0708 PM CDT Fri Jun 20 2025
Areas affected...Eastern North Dakota into northwest Minnesota
Concerning...Severe potential...Watch likely
Valid 210008Z - 210245Z
Probability of Watch Issuance...95 percent
SUMMARY...Watch issuance is expected this evening across eastern
North Dakota into northwest Minnesota. However, timing remains
uncertain given the potential for isolated supercells ahead of a
more widespread convective complex moving out of southwest North
Dakota. Additionally, an upgrade to a wind-driven Moderate risk is
forthcoming in the 01z Day 1 Convective Outlook for portions of the
region.
DISCUSSION...Discrete to semi-discrete cells developing across
southwest ND are expected to spread east into eastern ND though the
evening hours. As this occurs, they will encounter an increasingly
moist/buoyant air mass that is currently in place across southeast
ND (evident by dewpoints in the upper 60s to low 70s). This will
promote convective intensification as the band of cells undergoes
upscale growth into an organized line and begins to pose a more
widespread severe wind threat, including the potential for
significant wind gusts upwards of 80-90 mph.
Ahead of this band, more isolated discrete supercells appear
possible across southeast ND. Surface observations across the
western and central Dakotas are reporting surface pressure falls on
the order of 1-2 mb over the past hour, indicative of increasing
broad scale ascent over the region. This ascent is also manifesting
as mid-level stratus along the ND/SD border, which is coincident
with a maximum in low-level theta-e advection. The stable nature of
the stratus suggests that some MLCIN remains in place, but this
should continue to diminish over the next couple of hours as ascent
continues to spread east in tandem with a mid-level perturbation
currently upstream across western ND. Latest high-res guidance
suggests initiation within this regime is possible between 00-02
UTC, and any storms that can develop will likely become robust
supercells given the very favorable parameter space (MLCAPE
estimates between 3000-4000 J/kg and 50-60 knots of effective bulk
shear). In addition to the potential for very large hail, strong
low-level SRH within the warm frontal zone will also promote a
tornado risk with any supercells that can develop. However, there
remains some uncertainty regarding convective coverage and timing
within this area given the residual capping and comparatively weaker
forcing for ascent.
Regardless, watch issuance is expected within the next few hours as
either 1) initiation within the warm frontal zone becomes more
apparent, or 2) as the convective band across western ND spreads
east and intensifies.
..Moore/Smith.. 06/21/2025
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FGF...ABR...BIS...
LAT...LON 45849697 45859844 45960034 46170107 46710114 47180101
47440080 47620059 48249962 48709844 48899764 48889712
48749663 48299597 47769578 47119578 46559595 46089626
45869660 45849697
MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH
MOST PROBABLE PEAK WIND GUST...75-90 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN
Category: Watches, Warnings, Advisories, & Hazards