SPC MD 2048


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Mesoscale Discussion 2048
NWS Storm Prediction Center Norman OK
0324 PM CDT Tue Oct 01 2019

Areas affected...southwest IA

Concerning...Tornado Watch 670...

Valid 012024Z - 012130Z

The severe weather threat for Tornado Watch 670 continues.

SUMMARY...The potential for a supercell tornado is focusing over
southwest IA during the next 1-2 hours.  If low-level shear
increases further, this potential could be realized via a tornado.

DISCUSSION...Radar imagery shows a cluster of supercells and
developing thunderstorms south/east of a stationary front from the
MO River at the NE/MO/IA border into southwest IA.  Surface
conditions in southwest IA indicate temperatures are in the
lower-middle 80s degrees F with dewpoints in the lower-middle 70s.  

It appears one of the primary factors influencing the potential for
tornadogenesis over the next 1-2 hours is the forecast increase in
low-level shear and enlargement of the low-level hodograph.  The
ingredients of a favorable storm mode (i.e., multiple supercells)
and a moist/unstable boundary layer are present.  Forecast model
wind profiles in the lowest 2km are continuing to show hodograph
enlargement with 0-1 SRH increasing from around 50-100 m2/s-2 to
200-250 m2/s-2 between 20z and 23z, respectively.  It seems some of
the increase in SRH is due to the backing of near-surface flow
during this timeframe.  Will continue to monitor surface observation
trends over the next few hours to see if this forecast-model signal
is manifested in surface observations.

..Smith.. 10/01/2019

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


LAT...LON   41369468 40919549 40619564 40689482 41259421 41369468 

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