U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 231723 
Storm Prediction Center ac 231723 

Day 2 convective outlook corr 1 
National Weather Service Storm Prediction Center Norman OK 
1223 PM CDT sun Sep 23 2018 

Valid 241200z - 251200z 

..there is a marginal risk of severe thunderstorms over a portion 
of the Tennessee and Ohio valleys... 

Corrected for categorical graphic 

A strong thunderstorm or two may impact portions of the Tennessee 
and lower Ohio Valley Monday afternoon and evening, accompanied by a 
marginal risk for severe weather. 


A positive-tilt upper trough currently over the northern rockies 
will advance east through the northern plains and upper MS valley 
region Monday. A weaker southern-stream shortwave trough now over 
the lower MS valley will move northeast through the Tennessee and Ohio 
valleys. The northern-stream trough will be accompanied by a cold 
front through the upper MS valley. Farther south, the western 
portion of a quasi-stationary front now from the Carolinas westward 
into the Tennessee Valley will lift north as a warm front into the Ohio 
Valley region. 

..Tennessee into the Ohio Valley... 

A modest southerly low-level jet is forecast to develop in response 
to forcing associated with the southern-stream trough, and this 
feature will migrate northward through the Tennessee and Ohio valleys. A 
moist warm sector with low 70s f dewpoints will reside in warm 
sector south of the warm front, but weak lapse rates with areas of 
clouds and ongoing rain within plume of deep subtropical moisture 
will limit destabilization potential. Nevertheless, at least weak 
instability with 500 j/kg MLCAPE will exist, and low-level 
hodographs will increase in size along the low-level jet axis, 
though flow through a deeper layer will remain weak. This 
environment may support at least a marginal risk for a couple of 
transient rotating updrafts and northeast-moving bowing segments 
with primary threats being locally strong wind gusts and a brief 

..upper Mississippi Valley region... 

Overall severe potential in this region appears very limited. 
Widespread clouds, weak lapse rates and limited low-level moisture 
with dewpoints in the 50s f will result in very weak instability 
with MLCAPE near or below 300 j/kg. Showers and possibly isolated 
thunderstorms should develop within the zone of deeper ascent along 
the cold front from Minnesota into eastern SD, and this activity will be 
embedded within a kinematic environment favorable for severe storms 
with sfc-6 km shear around 40-45 kt. However, the very marginal 
thermodynamic environment is expected to limit the severe threat in 
this region. 

..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 5% - marginal 
hail: <5% - none 

.Dial.. 09/23/2018