U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 220059 
Storm Prediction Center ac 220058 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0758 PM CDT Sat Oct 21 2017 

Valid 220100z - 221200z 

..there is an enhanced risk of severe thunderstorms across parts of 
southeast Kansas...southwest Missouri...northwest Arkansas...a large 
portion of Oklahoma...and portions of North Texas... 

..there is a slight risk of severe thunderstorms surrounding the 
enhanced risk...extending from northern Missouri to central Texas... 

..there is a marginal risk of severe thunderstorms surrounding the 
slight risk area...from parts of Wisconsin and southeast Minnesota 
to Texas... 

Scattered severe thunderstorms will continue this evening and into 
the overnight hours across parts of the southern/Central Plains. 
Large hail, damaging winds, and a few tornadoes will all be 
possible, primarily across the Southern Plains. 

..upper Mississippi Valley to Texas tonight... 
Steady advance of a surface cold front across the central U.S. Is 
forecast tonight, eastward toward/across the upper and middle 
Mississippi Valley and southeast across the Southern Plains. 
Showers and thunderstorms are ongoing along the front at this time 
from northern Minnesota to western North Texas -- with the strongest 
storms -- including a few supercells -- indicated from central 
Oklahoma south-southwest to western North Texas. 

These stronger storms are ongoing within the region of greatest 
instability, with mixed-layer cape roughly 1500 to 2000 j/kg within 
this zone. With time, storm clustering/upscale growth toward a 
quasi-linear configuration along -- and just to the rear of -- the 
advancing front is expected, and thus threat will trend more toward 
damaging winds and some hail, as convection shifts east and 
southeast across the lower Missouri Valley/Ozarks/Southern Plains. 
In the short term however, while convection maintains some local 
cellular characteristics in that central Oklahoma to North Texas 
zone, large hail and the potential for a couple of tornadoes will 

.Goss.. 10/22/2017 


Mesoscale Discussion

acus11 kwns 220135 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 220134 

Mesoscale discussion 1729 
National Weather Service Storm Prediction Center Norman OK 
0834 PM CDT Sat Oct 21 2017 

Areas affected...central/eastern OK and North Texas 

Concerning...Tornado Watch 503...504... 

Valid 220134z - 220300z 

The severe weather threat for Tornado Watch 503, 504 continues. 

Summary...primary hazard should be strong to severe wind gusts with 
an accelerating line of storms moving east, but a couple brief 
tornadoes will remain possible within embedded mesovortices. 

Discussion...an extensive qlcs extends from southeast Minnesota into 
northwest Texas. Strong to severe wind gusts of 45-60 mph have been 
common per OK mesonet sites. This should remain the primary hazard 
as the line progresses east in tandem with a convectively reinforced 
cold front, likely reaching the Tulsa Metro area around 10 PM. With 
surface dew points in the middle 60s and 0-1 km srh around 300 m2/s2 
per tlx/inx vwp data, transient mesovortices will pose a risk for a 
couple brief tornadoes along the line. The progressive, surging 
nature of the composite outflow/front should mitigate a greater 
tornado threat. 

.Grams.. 10/22/2017 

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


Latitude...Lon 36859623 36869474 36329405 34639456 33379630 32759821 
32719960 33099978 33939892 36859623