Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 200156
SPC MCD 200156

Mesoscale Discussion 1659
NWS Storm Prediction Center Norman OK
0856 PM CDT Tue Sep 19 2017

Areas affected...eastern Dakotas/western Minnesota

Concerning...Tornado Watch 487...

Valid 200156Z - 200400Z

The severe weather threat for Tornado Watch 487 continues.

SUMMARY...Severe/isolated tornado risk continues across valid
portions of Tornado Watch 487.

DISCUSSION...Latest radar loop shows increasingly linear-mode
convection evolving near/ahead of the cold front slowly advancing
across the Dakotas.  While VAD wind profiles continue to reveal a
veering/increasing flow field with height supportive of updraft
rotation -- and thus some tornado risk, primary threat should
continue to trend more toward hail/wind given modal evolution.

At this time, convection remains generally contained within WW
bounds, but will continue spreading eastward with time.  However,
loss of diurnal heating and a less unstable airmass across most
areas east of the watch (with the exception of southwest Minnesota
where 1000 to 2000 J/kg mixed-layer CAPE is indicated) may limit
severe risk east of WW 487.  We will continue to monitor convective
and environmental evolution as storms near the eastern fringe of WW
487 for possible new WW issuance.

..Goss.. 09/20/2017

...Please see for graphic product...


LAT...LON   43769683 43509856 43869984 44920038 47099984 48750005
            49019531 47389528 43799655 43769683 is the U.S. government's official web portal to all federal, state and local government web resources and services.