SPC MD 1470


MD 1470 Image

Mesoscale Discussion 1470
NWS Storm Prediction Center Norman OK
1236 AM CDT Wed Aug 12 2020

Areas affected...North-Central/Northeast South Dakota

Concerning...Severe potential...Watch possible 

Valid 120536Z - 120700Z

Probability of Watch Issuance...40 percent

SUMMARY...Ongoing mesoscale convective system is expected to persist
eastward into more of north-central and northeast SD. Potential for
damaging wind gusts exists with this system and trends will be
monitored closely for downstream watch issuance.

DISCUSSION...A strong to occasionally severe MCS continues to move
east-southeastward across north-central SD at 35 kt. At this speed,
the system will reach the edge of Severe Thunderstorm Watch 432
before 06Z. Steep mid-level lapse rates downstream support moderate
to strong buoyancy, with recent mesoanalysis estimating MLCAPE
around 2500 J/kg. Vertical shear is modest (i.e. effective bulk
shear around 35 kt), but still strong enough to support persistence
of the ongoing cluster. Additionally, recent radar trends have shown
a tendency toward slightly faster easterly motion over the past half
hour or so. KABR velocity data also shows strong inbounds around
14-15 kft, indicating the presence of a rear-inflow jet. All of
these factors suggest the system is organized enough to persist
downstream for at least the next several hours. Low-level stability
may prevent strong gusts from reaching the surface at max strength.
However, a strengthening low-level flow ahead of the line could
moisten low-levels enough to reduce the low-level stability,
increasing the potential for damaging wind gusts. Trends will be
monitored closely for potential downstream watch issuance.

..Mosier/Hart.. 08/12/2020

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


LAT...LON   45740097 45870007 45729818 44459824 44469946 44930117

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