U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 241717 
Storm Prediction Center ac 241717 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1217 PM CDT sun Jun 24 2018 

Valid 251200z - 261200z 

..there is a slight risk of severe thunderstorms for 
Iowa...northern Missouri...and western Illinois... 

A few severe thunderstorms are possible across Iowa, northern 
Missouri and western Illinois on Monday. 

A mid-level shortwave trough over the north-Central High plains 
midday Sunday will evolve into a closed low and migrate east through 
the middle MO valley and into the upper Midwest by daybreak Tuesday. 
A belt of strong mid-level flow will move through the base of the 
trough over the lower MO valley. An occluded surface low is 
forecast over eastern NE with a warm frontal zone draped east into 
the middle MS valley. A myriad of convective outflow will serve as 
an effective front over eastern KS/OK. 

Farther west, a disturbance will move into the northern rockies with 
attendant mid-level height falls overspreading the northern High 
Plains primarily from Monday evening into the overnight. 

---A low-confidence/highly conditional forecast remains unchanged 
from the previous outlook.--- Scattered storms are likely to be 
ongoing throughout the day along the advancing warm front, from MO 
into Iowa and Illinois. While this may reduce instability, the air mass 
will be very moist, and low-level shear will be enhanced along the 
warm front. If instability develops similar to some model 
depictions, the threat for a few supercells may materialize. 
However, this potential outcome is highly conditional and is 
somewhat dependent on the evolution of convective outflow prior to 
the day2 period and the quality of moisture/destabilization along 
the boundary Monday afternoon. Other thunderstorms are possible by 
afternoon ahead of the weak low, from near the NE/Iowa border across 
Iowa. Marginal hail and locally damaging wind will be possible as 
well. The potential for widespread precipitation does decrease 
predictability for this scenario, and areal adjustments in future 
outlooks are possible. 

..lower Ohio Valley into the Carolinas... 
Models indicate ongoing storms Monday morning across Kentucky and Tennessee as 
westerly 850 mb winds maintain moist/warm advection. This activity 
may persist or regenerate later in the day downstream toward the 
Carolinas, tracking along the front. Locally damaging wind or hail 
will be possible. 

One forecast scenario, partially depicted in model guidance, 
involves an mesoscale convective vortex over the Ozarks midday Sunday moving east into NC by 
mid afternoon Monday. Enhanced flow in the mid levels associated 
with this feature may augment the risk for severe thunderstorms in 
the form of damaging gusts. If this possibility becomes increasing 
probable, higher severe probabilities may be introduced in later 

..maximum risk by hazard... 
Tornado: 5% - slight 
wind: 15% - slight 
hail: 5% - marginal 

.Smith.. 06/24/2018