MD 1176 CONCERNING SEVERE POTENTIAL…SEVERE THUNDERSTORM WATCH LIKELY FOR PORTIONS OF THE WESTERN INTO CENTRAL DAKOTAS
Mesoscale Discussion 1176
NWS Storm Prediction Center Norman OK
0314 PM CDT Tue Jun 20 2023
Areas affected...portions of the western into central Dakotas
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 202014Z - 202145Z
Probability of Watch Issuance...80 percent
SUMMARY...The severe threat is increasing across western and central
parts of both North Dakota and South Dakota, with large hail and
severe gusts the primary hazards. A Severe Thunderstorm Watch
issuance will likely be needed.
DISCUSSION...Convective initiation is underway ahead of an
approaching surface cold front, driven by low-level deep-moisture
convergence, and gradually increasing upper-level divergence
associated with the approaching mid-level trough. Mostly clear skies
ahead of the cold front has allowed for ample destabilization of the
boundary layer. Surface temperatures have warmed to over 90 F, amid
mid 60s F dewpoints, yielding over 3000 J/kg MLCAPE (given 7.5+ C/km
mid-level lapse rates overspreading the Dakotas), with CINH erosion
noted in the 20Z mesoanalysis. Mid-level flow is roughly parallel
with the surface cold front, with the stronger speed shear (i.e. 40+
kts of effective bulk shear) lagging the front to the west.
Nonetheless, ample buoyancy and modest deep-layer shear attempting
to precede the cold front will support the development of several
multicell clusters, short line segments, and perhaps a transient
supercell, all of which will be capable of producing severe
hail/winds. Given the number of storms expected ahead of the surface
cold front, a WW issuance will likely be needed.
..Squitieri/Hart.. 06/20/2023
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABR...BIS...LBF...UNR...
LAT...LON 45950224 47710157 48570087 48740030 47800020 45750018
44540018 42980048 41990064 41550107 41600204 42770240
43710239 45950224
