U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 200101 
Storm Prediction Center ac 200100 

Day 1 convective outlook 
National Weather Service 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... 

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 South Dakota 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 South Dakota. 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 forward 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 


Mesoscale Discussion

acus11 kwns 200053 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 200053 

Mesoscale discussion 1658 
National Weather Service Storm Prediction Center Norman OK 
0753 PM CDT Tue Sep 19 2017 

Areas affected...north-central Texas 

Concerning...severe potential...watch unlikely 

Valid 200053z - 200200z 

Probability of watch issuance...5 percent 

Summary...the small thunderstorm complex northwest of Dallas/Fort 
Worth will continue to pose a short-term threat of isolated damaging 
wind, before weakening later this evening. 

Discussion...the small thunderstorm complex that developed along the 
western edge of the deeper low-level moisture has thus far 
maintained its intensity and is now approaching the Dallas/Fort 
Worth area from the northwest. The recent forward sounding (modified for 
current surface conditions) shows moderate MLCAPE of around 1500 
j/kg and effective shear of around 25 kts, sufficient for some weak 
convective organization. The longevity of this system will be 
limited by increasing sbcinh with time as nocturnal cooling 
commences, though it may be sufficiently organized to last for 
another 1-2 hours as it approaches the metroplex. Given the 
increasingly linear nature of the convective system, the primary 
remaining severe threat should be in the form of isolated damaging 
wind, though some hail will also be possible with the strongest 

.Dean/Edwards.. 09/20/2017 

..please see www.Spc.NOAA.Gov for graphic product... 


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