ZCZC SPCSWOMCD ALL
ACUS11 KWNS 222351 
SPC MCD 222351 
IAZ000-NEZ000-SDZ000-230045-

Mesoscale Discussion 1065
NWS Storm Prediction Center Norman OK
0651 PM CDT Tue Jun 22 2021

Areas affected...eastern Nebraska into western and central Iowa

Concerning...Severe Thunderstorm Watch 305...

Valid 222351Z - 230045Z

The severe weather threat for Severe Thunderstorm Watch 305
continues.

SUMMARY...Hail and damaging wind gusts will remain likely with the
stronger storms across WW305 and the vicinity over the next couple
of hours. Storm coverage and intensity should begin to decrease
close to sunset.

DISCUSSION...Several supercells ongoing across WW305 and surrounding
areas have produced numerous severe hail and isolated wind reports
over the last 90 minutes. SPC mesoanalysis indicates the strongest
storms are ongoing in a narrow axis of 500-1500 J/kg of MLCAPE
stretching from northeast Nebraska into central Iowa. 45-55 kt
effective shear values from the OAX VWP suggest the storm mode will
likely remain supercellular as storms track southeast over the next
2-3 hours. Given the favorable storm mode and available instability,
severe hail and damaging wind gusts will remain likely.

Approaching sunset, storms across eastern Nebraska and western Iowa
will approach a much drier airmass near the Omaha metro. Deep mixing
has resulted in substantially lower surface dewpoints across this
region, severely degrading available buoyancy. As storms approach
this region, a decrease in severe weather probabilities appears
likely. A similar scenario is expected to unfold farther east across
central Iowa as storms approach the eastern edge of the instability
axis coincident with the loss of diurnal heating. Updraft strength
should gradually diminish as nocturnal inhibition increases and
storms move into a more hostile environment north of a stationary
front.

..Lyons.. 06/22/2021

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

ATTN...WFO...DVN...DMX...FSD...OAX...GID...LBF...

LAT...LON   41059726 41299830 41979857 42439768 42659673 42689592
            42589396 42149283 41659239 41419222 40999217 40639258
            40629382 40719505 40969618 41059726 

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