ACUS11 KWNS 181953
SWOMCD
SPC MCD 181953=20
MNZ000-SDZ000-NEZ000-182230-

Mesoscale Discussion 2083
NWS Storm Prediction Center Norman OK
0253 PM CDT Wed Sep 18 2024

Areas affected...parts of eastern South Dakota...adjacent
northeastern Nebraska and southwestern Minnesota

Concerning...Severe potential...Watch possible=20

Valid 181953Z - 182230Z

Probability of Watch Issuance...40 percent

SUMMARY...The initiation of one or two strong storms appears
possible late this afternoon. Sustained storm development may
include the evolution of supercell structures posing a risk for
severe hail, and perhaps some potential for a tornado by early
evening. Due to the isolated nature, it is not certain that a
severe weather watch is needed, but trends are being monitored.

DISCUSSION...Although stronger mid-level height falls appear to be
shifting to the north, a destabilizing warm sector boundary layer
across the eastern South Dakota vicinity will remain beneath weakly
difluent cyclonic mid-level flow into early evening. With
mixed-layer CAPE now on the order of 1500 J/kg, beneath 30-50 kt
southwesterly mid/upper flow, the environment appears at least
conditionally supportive of supercells, and low-level hodographs may
enlarge with clockwise curvature as southerly flow around 850 mb is
forecast to strengthen some (to around 30+ kt) through 22-00Z.

Although low-level forcing for sustained convective development
remains unclear, weak warm advection to the east of the dryline may
be supporting ongoing attempts at deepening convection east of Huron
into the Watertown vicinity. And objective analysis has indicated a
persistent localized area of enhanced convergence along a confluence
zone near/west of Yankton.

Model output, including the convection allowing guidance, suggest
that probabilities for thunderstorm development are generally low
into early evening. However, the initiation of one or two storms
appears possible. If this is sustained, this may include the
evolution of supercell structures posing a risk for severe hail, and
perhaps some potential for a tornado.

..Kerr/Gleason.. 09/18/2024

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!5g-wD-kly1eLMPW7XcgHCC6A6XN8r27jIPloUOuMjF7GM67GwTqCDUKF-BKsSy6yULHA8rd9z= o_QvX7aIw4UavTSdcs$ for graphic product...

ATTN...WFO...MPX...FSD...OAX...ABR...LBF...

LAT...LON 45389647 44609622 42819716 42949859 44379830 45219788
45549726 45389647=20


=3D =3D =3D
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