Severe Storm Outlook Narrative (AC)
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000
ACUS01 KWNS 200101
SWODY1
SPC AC 200100

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Tue Sep 19 2017

Valid 200100Z - 201200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
EASTERN DAKOTAS INTO WESTERN MINNESOTA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE EASTERN
DAKOTAS INTO CENTRAL MINNESOTA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE EASTERN
DAKOTAS INTO NORTHWEST WISCONSIN...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A SMALL
PORTION OF NORTH-CENTRAL TEXAS...

...SUMMARY...
Significant severe storms capable of damaging winds, tornadoes and
large hail are expected across parts of the eastern Dakotas into
western Minnesota through tonight.

...Eastern Dakotas into Minnesota...
Cooling and increasing winds aloft continue to overspread the region
this evening. A line of pre-frontal storms has formed over
east-central SD into southeast ND, with northern sections of this
line intersecting a recent outflow boundary. Shear profiles are
impressive, with ample shear and SRH to support both supercells and
damaging bows (as seen on 00Z ABR sounding). Surface observations
indicate temperatures only in the 70s over much of the area, the
exception being far southern SD. This could be one factor leading to
slow transition to supercells. However, as the very strong shear
continues to act on the developing cells, the supercell and tornado
threat may increase. The higher-end severe probabilities have been
shunted a bit farther south toward I-90, due to the presence of a
warmer low-level air mass. Additional storms will also form along
the surging front, with more of a linear storm mode/QLCS taking
shape later this evening. For more information see mesoscale
discussion 1657.

...North-central Texas...
A small cluster of storms has developed south of the Wichita Falls
area, and is beginning to propagate in a southeastward direction.
This cluster formed during the heat of the day, and is now being
driven by it`s own outflow. Conditions downstream are quite warm
with the 00Z FWD sounding showing a well-mixed boundary layer with
minimal CIN. Locally strong wind gusts, possibly severe, may
approach the Metroplex this evening before the cells dissipate. For
more information see mesoscale discussion 1658.

..Jewell.. 09/20/2017

$$



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