SPC MD 1422


MD 1422 Image

Mesoscale Discussion 1422
NWS Storm Prediction Center Norman OK
1206 PM CDT Sat Aug 08 2020

Areas affected...Portions of far eastern SD into western/northern MN

Concerning...Severe potential...Watch unlikely 

Valid 081706Z - 081900Z

Probability of Watch Issuance...20 percent

SUMMARY...A threat for isolated large hail and severe wind gusts may
persist through the early afternoon with widely spaced storms. Watch
issuance appears unlikely for now, but trends will be closely

DISCUSSION...Convection has persisted through the morning along or
just behind a surface cold front across far eastern SD and northern
MN. An MCV from earlier storms currently over southeastern ND should
continue east-northeastward into northern/central MN this afternoon.
The 12Z sounding from ABR shows a very strong cap in the low levels,
and the storms occurring across far eastern SD may remain elevated
through much of the day. RAP forecast soundings suggest the
low-level inversion is less pronounced with northward extent into
northern MN, and there may be a slightly better chance for
surface-based storms across this area.

Steep mid-level lapse rates have overspread the frontal zone, and
2000-3000 J/kg of MLCAPE is already present at 17Z. Modestly
enhanced mid-level winds associated with the MCV and shown in recent
VWPs from KABR should promote storm organization with any storms
that can persist or develop along/near the front this afternoon.
Given this favorable combination of moderate to strong instability
and sufficient deep-layer shear, isolated instances of large hail
and severe wind gusts appears to be the primary threats with the
more robust storms. Main uncertainty is overall storm coverage along
the front given the pronounced cap, especially with southward
extent. Widespread cloudiness across western/central MN may also
limit the development of steep low-level lapse rates, slow diurnal
heating, and delay the erosion of the cap. Given these
uncertainties, watch issuance does not seem likely at this time,
although observational and convective trends will be closely

..Gleason/Grams.. 08/08/2020

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


LAT...LON   46489384 46159407 44959530 44479650 44549725 44819764
            45969644 47069580 47459518 47429393 46989375 46489384 

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