Severe Weather Outbreak Possible This Afternoon
First of all, I don’t use those words lightly. Have a plan in place now. Prepare for the potential of significant severe weather to take place this afternoon now. The Storm Prediction Center has issued a “Moderate” risk of severe thunderstorms this afternoon. Think of this as a level 4 out of 5 risk, meaning there’s a high confidence of significant severe weather. Along and east of I-65, the main hazards include very large hail, damaging winds, and tornadoes (some of which can be strong and long-track).
Current Conditions (5 AM)
Looking at GOES-16 satellite data, there are a lot of features to take note of. First of all, to the north of the Ohio River, there’s abundant high level clouds. This is likely spreading off convection to the west. This may lead to a decreased severe threat north of the Ohio River. However, south of the river, there are hardly any clouds. Also, a residual outflow boundary has been pushed by convection. This may serve as a focus for thunderstorm initiation later today.
Relatively dry air is in place across the region. Dew point temperatures as of 5 AM are not indicative of a severe thunderstorm risk. However, dew point temperature (moisture) will increase throughout the day. By Noon, dew point temperatures should be in the mid to upper 50s across the region. This will allow for sufficient destabilization this afternoon for severe thunderstorms. If dew point temperatures do not rebound as high as expected, a lower severe threat could evolve.
In the upper levels of the atmosphere, a trough is oriented to the west. A jet streak of 100 knots is rounding the base of the trough. Widespread divergence is noted across the upper Mississippi Valley. This is leading to the widespread cloud cover and precipitation seen in the satellite image above.
In the low levels of the atmosphere, moderate to weak southwest flow exists. A low level jet of 30 to 40 knots is noted across the Mississippi Valley. Low level moisture is less than impressive, however this will need to be tracked over time.
All models are in good agreement that dew point temperatures climb into the upper 50s, to perhaps low 60s across the region. If this forecast could be busted by anything, it will be by moisture. If moisture return is less than forecast, a lower severe weather threat will be realized. If better moisture return occurs, a more significant severe weather threat could evolve. High temperatures should top out in the upper 70s to perhaps even 80° this afternoon.
Increasing moisture will lead to increasing instability along and east of I-65. This will happen in conjunction with an upper level jet streak rounding the base of the aforementioned trough. Add in the progression of the outflow boundary, and you should be left with explosive thunderstorm development in the early afternoon, just west of I-65.
During initiation of thunderstorms to the west, southerly surface winds can be expected. The low-level jet will have wind vectors out of the south-southwest. This will lead to a bit of directional shear in the low levels of the atmosphere, leading to an increasing tornado threat. Dry air aloft will lead to a very large hail and damaging wind threat as well.
The National Weather Service in Louisville, Kentucky believes the time frame of most concern is between 3 PM and 8 PM for central Kentucky. This falls in line with my forecast as well.
We’ll bring more updates later today. Be sure to have a plan in place for severe weather warnings. As always you can follow @wxornotBG and @JacobWilkinswx for the latest severe weather coverage. For good skycam information in Bowling Green, be sure to follow @WKUweather. Lastly, like Landon Hampton on Facebook for video forecast updates.
-Meteorologist Jacob Wilkins