SPC MD 1367


MD 1367 Image

Mesoscale Discussion 1367
NWS Storm Prediction Center Norman OK
0254 PM CDT Fri Jul 31 2020

Areas affected...southwest North Dakota and western South Dakota

Concerning...Severe potential...Watch unlikely 

Valid 311954Z - 312200Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms will continue to develop/strengthen this
afternoon. Conditions will be favorable for isolated damaging
thunderstorm winds and some hail. Conditions will continue to be
monitored for potential need for a Severe Thunderstorm Watch, but
one is not currently anticipated.

DISCUSSION...Thunderstorms are developing/strengthening on the
eastern edge of a mesoscale convective vortex (MCV) across eastern
Montana. These thunderstorms should continue to develop and increase
in both strength and coverage this afternoon as the MCV interacts
with a surface front moving south across North Dakota. The overall
movement of the MCV and surface boundary, coupled with northerly
mid-level flow, favor a south to southeast storm motion.

Instability appears to be maximized to the east of the ongoing
thunderstorms/MCV where surface temperatures have warmed into the
80s F and dewpoints are currently in the 60s F, leading to
most-unstable CAPE on the order of 2000-3000 J/kg with little-to-no
surface inhibition left. However, deep-layer shear is rather weak,
except locally/sub-synoptically augmented to the east of the MCV,
which should limit the overall organizational potential of any
thunderstorm updraft/downdraft pairs. 

Given the degree of instability, a surface boundary, and an MCV all
interacting with one another, strong-to-severe multi-cell
thunderstorms are possible across the region this afternoon.
Mid-level lapse rates around 7 C/kg may support an isolated
hail/large-hail risk with the strongest updrafts, however, potential
strong thunderstorm winds associated with developing/congealing cold
pools will be the more likely threat. 

The lack of stronger shear and the pulse-based nature of any severe
thunderstorm should preclude the need for a severe thunderstorm
watch, but conditions will continue to be monitored.

..Marsh/Bunting.. 07/31/2020

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


LAT...LON   45580330 47200301 46650025 44719978 44490149 45580330 

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