U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus03 kwns 180707 
Storm Prediction Center ac 180706 

Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0206 am CDT Wed Jul 18 2018 

Valid 201200z - 211200z 

..there is a slight risk of severe thunderstorms across parts of 
the middle Mississippi...Ohio and Tennessee valleys... 

A severe threat will be possible on Friday across parts of the mid 
Mississippi, Ohio and Tennessee valleys... 

..mid Mississippi/Ohio and Tennessee valleys... 
An upper-level trough will become more amplified and move 
east-southeastward into the western Great Lakes region on Friday as 
a 50 to 65 kt mid-level jet moves through the southwestern part of 
the system. At the surface, a low is forecast to move into the 
western Great Lakes as a cold front advances eastward into the lower 
Ohio Valley. Elevated thunderstorms could be ongoing in the morning 
well ahead of the front with this convection moving eastward away 
from the greatest instability during the day. Just ahead of the 
front, a moist airmass is forecast to be in place across much of the 
mid Mississippi, Ohio and Tennessee valleys where surface dewpoints 
should be in the upper 60s and lower 70s f. In response to surface 
heating, moderate to strong instability is forecast to develop from 
western Tennessee northward through western Kentucky and southern 
Indiana. Thunderstorm development will be possible along the 
northern side of the strongest instability from southeast Illinois 
southeastward into western and central Kentucky late Friday 

GFS forecast soundings at Paducah, Kentucky and Evansville, in for 
00z/Saturday show MLCAPE value around 3500 j/kg with 0-6 km shear in 
the 50 to 60 kt range. This combined with steep mid-level lapse 
rates should be favorable for supercells with large hail. A wind 
damage-threat and isolated tornado threat will also be possible. The 
wind-damage threat could become more prominent in the early evening 
as a cluster or line of storms moves southeastward across the Ohio 
and Tennessee valleys. 

Over the last few days, the models have been fairly consistent from 
run to run concerning friday's scenario. Also, the models are in 
decent agreement on the latest run suggesting that confidence is 
high enough to add a slight risk across parts of the lower Ohio 
Valley for Friday. 

.Broyles.. 07/18/2018