Possible Severe Weather Sunday 6/25/23

[nWo]

  A shortwave trough is forecast to progress from the Mid/Upper Mississippi Valley into the Upper Great Lakes/Lower Ohio Valley on Sunday. Thunderstorm development is expected across the Lower OH Valley during the afternoon, as the cold front associated with the shortwave trough moves through. There is some uncertainty regarding the amount of destabilization that occurs before the frontal passage, but strong mid-level flow will spread into the region. Conditions should be enough to produce severe thunderstorms. The highest probability of severe is currently expected across central/southern Indiana, southwest Kentucky, far southeast Illinois, and far northwestern Tennessee. The Storm Prediction Center already has these areas in a Slight Risk Area in the day 4 outlook. Once again there still remains uncertainty about the forecast that far out. I just wanted to inform everyone so you can prepare as you see fit in case severe weather occurs in your area.

 

 

[nWo]

I just received this communication from the NWS-Louisville office.

 

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Good afternoon -

We just wanted to give an early heads-up that strong or severe storms are possible on Sunday, especially in the late afternoon and evening, mainly along and west of I-65. Because we are 72 hours out, there is still uncertainty which hinges on just how far south and east any storms can get before daytime heating is lost. While damaging winds are the primary threat, large hail and tornadoes will also be possible.

Be sure to keep up with the latest forecasts through the weekend. We will provide our next update no later than Friday afternoon. IF the threat level increases, a conference call is possible Saturday afternoon.

If you have any outstanding questions or concerns, don't hesitate to email or call the office.

Thanks!
--NWS Louisville

 

 

[nWo]

Friday morning update:

 An upper-level trough will move eastward across the north-central states on Sunday, At the surface, a low will move into the western Great Lakes as a cold front advances southeastward into the mid-Mississippi Valley. Ahead of the front, surface dewpoints in the low to mid-70s F will contribute to a corridor of moderate to strong instability by early afternoon from western Tennessee into central and northern Kentucky. During the
   afternoon, Showers/storms are forecast to first initiate on the northern edge of the stronger instability, with storms moving eastward across the Ohio Valley during the mid to late afternoon. Storm coverage should continue expanding across the region during the
   early evening, with a band of storms moving east-southeastward into the central Appalachians, and southeastward into the Tennessee Valley. Thunderstorm complex development will be possible across parts of the Ohio and Tennessee Valleys.

  Conditions should be favorable for supercells with large hail. Hailstones greater than 2 inches in diameter will be possible. Wind damage will also be possible with supercells and the more intense line segments. A tornado threat may also develop. The severe threat could be upgraded to Enhanced Risk in later outlooks if model runs continue to show a greater coverage of the severe threat Sunday afternoon and evening. 

The Storm Prediction Center has most of Kentucky under a level 2 Slight Risk Area. Eastern Kentucky is under a level 1 Marginal Risk Area. A total of 33,537,407 people will be under this severe threat.

[nWo]

Saturday morning update:

A severe threat will be likely across parts of the mid-Mississippi, Ohio and Tennessee Valleys on Sunday. Large hail, wind damage, and perhaps a couple of tornadoes will be possible.

An upper-level trough will move eastward into the western Great Lakes region on Sunday, as a 50 to 60-knot mid-level jet dives into the Ohio Valley. At the surface, a cold front will advance southeastward into the mid-Mississippi Valley. Ahead of the front, surface dewpoints in the upper 60s and lower 70s F will contribute to an area of strong instability by afternoon. In the early afternoon, showers/storms are forecast to first initiate across eastern Illinois, far western Indiana, and lower Michigan. From this convection, thunderstorms are expected to form and move east-southeastward across the Ohio Valley. A complex of storm development will be possible, with a large convective cluster or line of storms affecting much of Kentucky, and Tennessee.

NAM forecast soundings in the vicinity of Louisville, Kentucky in the late afternoon, show conditions that could support supercells capable of producing large hail, wind damage, and a tornado threat. It appears that supercells with large hail will be most likely early in the event, but that the potential for severe multicell line segments with damaging wind gusts may increase later in the event. A lot will depend upon whether a linear complex of storms can become organized, and how quickly a cold pool can develop. There is also uncertainty concerning the exact track of potential storms, the timing of the upper trough, and the distribution of instability. An area of higher wind-damage threat could be later added once these factors become more clear.

I will post an update later today. 

 

 

 

The Hatched Area: 10% or greater probability of two inch diameter hail or larger within 25 miles of a point.

[nWo]

I have received the following email from the NWS-Louisville.

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Hello,

There continue to be indications that severe thunderstorms may develop on Sunday by mid to late afternoon and continue into the evening, before moving out of the area late Sunday night. If storms do form, they will be capable of damaging wind gusts, large hail, and possibly a few tornadoes.

However, there is still uncertainty in the forecast. A band of showers and thunderstorms Sunday morning may have an effect on how much the atmosphere can destabilize in the afternoon. Also, there is a layer of warm air aloft that may inhibit afternoon storm development. We will continue to work out the details today and tomorrow, so be sure to stay up-to-date with the latest forecasts. Our forecasts are updated at a minimum around 4am and 4pm EDT, with more frequent updates as conditions warrant.

Please feel free to reach out to us if you have any questions.

Sincerely,
National Weather Service, Louisville

 

 

[nWo]

I neglected to add these briefing slides with the email.