U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 170544 
Storm Prediction Center ac 170544 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1244 am CDT Tue Jul 17 2018 

Valid 181200z - 191200z 

..there is a marginal risk of severe thunderstorms across parts of 
the central and northern plains into the middle Missouri Valley... 

A marginal severe threat will be possible on Wednesday in parts of 
the central and northern plains into the mid Missouri Valley. 

..central and northern plains/mid Missouri Valley... 
A shortwave trough will move across the northern plains on Wednesday 
as a cold front moves across the northern High Plains. A broad 
corridor of maximized low-level moisture should be in place from 
eastern portions of the Central Plains into the northern plains with 
surface dewpoints in the mid to upper 60s f. This should enable 
moderate instability to develop by afternoon in areas that are not 
affected by morning convection. Model forecasts suggest that 
thunderstorms will form near the shortwave trough during the early 
to mid afternoon with a cluster moving southeastward across 
south-central South Dakota and into east-central Nebraska. GFS 
forecast soundings along this corridor during the late afternoon 
show MLCAPE values in the 1500 to 2500 j/kg range with 0-6 km shear 
in the 35 to 50 kt range. This should be a favorable environment for 
at least an isolated severe threat. However, the model spread for 
instability is considerable which introduces substantial 
uncertainty. For this reason, a marginal risk in the central and 
northern plains will be maintained for this outlook and adjusted 
spatially for the new data. 

..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 5% - marginal 
hail: 5% - marginal 

.Broyles.. 07/17/2018