U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 221722 
Storm Prediction Center ac 221721 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1121 am CST Fri Feb 22 2019 

Valid 231200z - 241200z 

..there is an enhanced risk of severe thunderstorms from a portion 
of the lower Mississippi Valley into the Tennessee Valley... 

Scattered severe storms are expected Saturday from a portion of the 
lower Mississippi and Tennessee valleys and possibly into western 
and central Kentucky. Damaging wind and tornadoes are the main 
threats, but hail is also possible. 


By 12z Saturday, Lee cyclogenesis will be well underway over the 
southern High Plains in association with a potent southern-stream 
shortwave trough now located over Arizona. This feature will continue 
into the southern and Central Plains and then northeastward into the 
middle MS valley tomorrow. By later Saturday afternoon the cyclone 
will be located over MO with a cold front trailing southward through 
Arkansas and la. A warm front should extend southeastward from the low 
through western Kentucky into middle Tennessee and Georgia. The surface low will 
occlude over the Great Lakes while the trailing front reaches the 
central and southern Appalachians by the end of the period. 

..lower Mississippi through Tennessee Valley regions... 

As of mid day a quasi-stationary front extends from the northwest 
Gulf through southern portions of the Gulf Coast states. Rich 
low-level moisture with upper 60s to near 70 f dewpoints resides 
south of this front. Farther north a rain-cooled boundary stretches 
from northeast Texas through northern portions of MS, Alabama and Georgia. A 
broad southerly low-level jet will increase tonight over the lower 
MS valley within the gradient zone between retreating high pressure 
and the developing Lee cyclone. This will promote northward advance 
of the warm front that will eventually merge with the rain-cooled 
boundary farther north. This consolidated boundary should reach 
central Arkansas and western Tennessee later Saturday morning, possibly 
continuing as far north as western Kentucky during the afternoon. Primary 
uncertainty this forecast is degree and northward extent of boundary 
layer destabilization, especially through west and central Kentucky. Most 
recent model runs including the cams suggest that much of Kentucky will be 
affected by areas of widespread rain and clouds within zone of 
isentropic ascent north of the warm front, with only a small window 
for modest surface-based destabilization before cold frontal 
passage. The rap, being the outlier, advances the unstable warm 
sector farther north. In either case, feel that at least a slight 
risk is warranted as far north as Kentucky given the favorable kinematic 
environment and some potential for surface-based destabilization. 

Otherwise, a corridor of modest surface-based instability (500-1000 
j/kg mlcape) is expected to evolve in warm sector over the lower MS 
and western Tennessee valleys within zone of Theta-E advection along the 
strengthening low-level jet. A band of thunderstorms will likely 
develop within this warm conveyor belt along and just ahead of the 
cold front from Arkansas into la by late morning and continue east during 
the afternoon. A strong mid-level jet rotating through base of the 
shortwave trough, coupled with the strengthening 50+ kt low-level 
jet, will promote very favorable wind profiles for severe storms. 
Large 0-2 km hodographs and 50+ kt effective bulk shear will support 
supercells with low-level mesocyclones and bowing structures capable 
of tornadoes and damaging wind, with peak period from afternoon into 
early evening. 

..maximum risk by hazard... 
Tornado: 10% sig - enhanced 
wind: 30% - enhanced 
hail: 15% - slight 

.Dial.. 02/22/2019