U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 181950 
Storm Prediction Center ac 181949 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0149 PM CST Sat Nov 18 2017 

Valid 182000z - 191200z 

..there is a slight risk of severe thunderstorms across the Ohio 
and Tennessee Valley regions... 

..there is a marginal risk of severe thunderstorms from northern 
Mississippi and Alabama into Ohio... 

Thunderstorms capable of severe wind gusts, marginal hail, or a 
brief tornado remain possible this afternoon across parts of the 
Ohio and Tennessee Valley regions, and into northern Mississippi and 

..Ohio and Tennessee valleys... 
A line of storms currently extends from west central Ohio 
southwestward into northeast Arkansas along a strong cold front. 
Ahead of this line exists a narrow corridor of instability, with the 
greatest Theta-E air into the lower Mississippi Valley where 
temperatures are approaching 80. Despite weak instability, very 
strong mean wind fields may produce gusts at or above severe levels 
anywhere along the line. For more information see mesoscale 
discussion 1770. 

.Jewell.. 11/18/2017 

Previous discussion... /issued 1022 am CST Sat Nov 18 2017/ 

..OH/Tennessee Valley region... 
Water vapor imagery shows a vigorous upper trough moving rapidly 
eastward across the Central Plains. Large scale forcing ahead of 
this feature is overspreading the mid MS and lower Ohio valleys, and 
should result in scattered afternoon thunderstorms. Storms will be 
focused along a cold front - initially over central/southern Illinois and 
southeast MO. This activity will spread eastward through the 
evening hours into parts of in/KY/TN. Wind fields are very strong, 
and are supportive of organized storms with bowing and supercell 
structures. However, low-level moisture and cape are quite limited 
today with dewpoints only in the 50s to lower 60s, and MUCAPE values 
below 1000 j/kg. Considerable cloud cover and slightly veered 
low-level winds are also negatives for a more robust severe event. 
Nevertheless, the initial storms over Illinois/MO and western Kentucky/Tennessee may 
produce large hail, with the risk of damaging winds increasing 
through the event farther east. A tornado or two is also possible 
in early supercells, and along the qlcs later today. 


Mesoscale Discussion

acus11 kwns 181949 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 181948 

Mesoscale discussion 1770 
National Weather Service Storm Prediction Center Norman OK 
0148 PM CST Sat Nov 18 2017 

Areas affected...western Kentucky to southwest Ohio 

Concerning...Severe Thunderstorm Watch 516... 

Valid 181948z - 182045z 

The severe weather threat for Severe Thunderstorm Watch 516 

Summary...severe threat is shifting east across ww516. Damaging 
winds remain possible. 

Discussion...frontal convection has gradually matured into a 
near-continuous squall line currently observed from central in, 
southwest into western Kentucky. This line of storms is progressing 
east-southeast near 30kt and should continue this motion across the 
remainder of ww516. This activity will soon advance east of greatest 
instability axis but damaging winds remain possible as environmental 
shear remains strong. 

.Darrow.. 11/18/2017 

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


Latitude...Lon 36559101 40848659 40848354 36568813 36559101