A significant tornado outbreak could be in the making for Wednesday afternoon into the early evening, especially for portions of Arkansas and Mississippi. Portions of Kentucky will also be under the gun for strong to severe storms capable of producing large to very large hail, damaging winds, and tornadoes. Some of the tornadoes could be strong. First, let's discuss Arkansas and Mississippi. The NAM SARS is showing 8.5-9.5 out of 11 for possible EF-4+ tornadoes for those states. This will be especially dangerous because some of these may form after sunset. I don't remember seeing numbers this high in the recent past.

Let's discuss the setup that may make all of this possible. A substantial severe threat is evident for a large portion of both the Ohio and Mississippi Valleys ahead of the cold front. Pronounced large-scale rising of air associated with the negatively tilted trough will likely overspread the warm air sector through the day. 60s surface dewpoints will be present ahead of the front, with greater low-level moisture likely in place from the Ohio Valley into the lower Mississippi Valley. Daytime heating of this airmass should allow for moderate to strong instability to develop by Wednesday afternoon. This along with deep layer shear is forecast to be quite strong. Prefrontal precipitation appears in possible partitions of the areas mentioned. If this occurs, then supercells posing a threat for all severe weather modes, including strong tornadoes, would be likely. A line storm is also expected to develop along much of the length of the front. This activity will pose a threat for both damaging winds and quick spin-up tornadoes as it spreads eastward Wednesday afternoon and evening. 

The Storm Prediction Center has a level 3 Enhanced Risk Area for parts of Kentucky west of I-65. A level 2 Slight Risk Area covers Kentucky from I-65 to just east of I-75. A level 1 Marginal Risk Area covers eastern Kentucky.

 

 

This shows the negatively tilted trough. These types of troughs produce the most severe weather. This is because there is strong southerly surface wind with its warm air underneath the incoming cold air in the upper atmosphere creating unstable conditions. 

 

Dewpoints

 

Radar

 

I will update you tomorrow on the conditions and timing. 

 

 

Tuesday morning update:

A line of strong to severe thunderstorms is expected to develop in advance of a cold front. These storms will make damaging winds, large hail, and isolated tornadoes possible. The highest risk remains along and west of I-65. Isolated severe storms are possible Wednesday afternoon, with a more widespread severe potential between 8 pm and 4 am EDT. The Storm Prediction Center has expanded the level 3 Enhanced Risk Area to just west of I-65. Louisville and Bowling Green are now included.

Update to come later today. Sooner if new information comes out.

 

Tuesday mid-day update:

Numerous severe thunderstorms appear likely across a large portion of the lower/mid Mississippi Valley into the Midwest, and lower Ohio Valley on Wednesday. Damaging winds, some of which could be significant, several tornadoes (some strong), and large to very large hail will likely occur. Warm are will move in and replace cool air ahead of the cold front. This plus upper level winds of around 65+ knots may support a few discrete cells especially in western Kentucky by mid to late afternoon. This potential may be conditional on the degree of destabilization that can occur behind  early-morning rain/weak thunderstorms that should exit the region by early afternoon. However, if discrete storms can become established, all hazards will be possible, including the potential for large hail and strong tornadoes.

The Storm Prediction Center has raised the threat level west and north of a line from around Owensboro southwestward just east of Madisonville to a level 4 Moderate Risk Area.

 

Those west of I-65 should be going over their emergency action plan today. Check back for any update this evening

Man oh man, mother nature needs to give the Jackson Purchase a break...

Tuesday evening update:

The severe weather threat for Wednesday afternoon and night continues. One thing we need to watch is how fast the cold front moves into Kentucky. If it moves in faster then the severe threat will increase and extend further east. I would not be at all surprised that the Level 4 Moderate Risk Area is extended eastward. One new thing from the HRRR model guidance is that the tornado threat, while low, could now reach southeastern Indiana along with the Cincinnati/NKY area Wednesday night. Also possible will be supercell thunderstorms that could form ahead of the cold front. Especially in western Kentucky. The HRRR Radar shows this possibility. The period covered is from 2 pm EDT to 7 am EDT Thursday.

The EHI shows that atmospheric conditions could be such that severe weather could form.

 

Supercell

 

Significant Tornado

 

 

One thing of note.  Everyone should be weather-aware Wednesday. Let me reiterate everyone should be going over their emergency action plan tonight. Especially west of I-65. Also have more than one way to get emergency weather announcements for your area. 

 

I will post an update early tomorrow morning. 

Thank You @nWofor keeping us in the know!

8 hours ago, Jumper_Dad said:

Thank You @nWofor keeping us in the know!

You're welcome