The Bottom Line
Central/North Mississippi: Severe weather will be possible starting in the late morning hours tomorrow and extend until likely just after 7pm. Supercell thunderstorms could form in front of a main squall line in the early afternoon and produce some tornadoes, but this will be highly dependent on some "iffy" factors like the cap and surface winds. Straight line wind damage, large hail, and some embedded brief tornadoes will be possible with an approaching squall line of storms as we get closer to sunset.
West Tennessee: A squall line of storms will travel from west to east tomorrow between the late morning and middle afternoon hours. This line will strengthen due to daytime heating as it travels eastward, so be especially on the lookout if you live east of Jackson, TN. There's also a possibility for the development of a supercell or two in the southern portions of West Tennessee before the passage of the main line of storms. Straight line winds, hail, a few brief tornadoes, and flash flooding will be possible as the squall line passes through.
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Severe weather will be an issue tomorrow around the South as a sharp trough and accompanying cold front advance eastward. The Storm Prediction Center has already put a large portion of the Southeast US under a Slight Risk for severe weather tomorrow, putting particular emphasis on an enhanced severe threat in Mississippi, Alabama, and Tennessee with a 30% outlined area. The SPC's outlook calls for the chance of discrete superecells in front of a main squall line, or QLCS, of storms that could bring damaging winds and some embedded tornadoes.
Here in Mississippi and West Tennessee we'll be watching for a particular area where the most favorable wind shear and instability will come together to create the greatest threat for severe weather. Wind profiles will be most favorable for severe weather as you go northward into Tennessee and Kentucky, but instability will be strongest over Central and North Mississippi as we head into the afternoon hours tomorrow. The meeting of these two "peak" areas of winds and instability will likely be North Mississippi into North Alabama and extreme Southwest Tennessee. The SREF computer model's Significant Tornado Ingredients parameter on the image to the right shows a pretty good estimate of where this area will be during the afternoon tomorrow in the 20 and 30 outlined areas.
With the threat of supercells in the early afternoon and the squall line near nightfall, this will be a fairly long event. There isn't one particular parameter that sticks out as being "historic" or much above average for any severe weather event. The significance here is that each of these parameters (instability, shear, moisture, etc) will meet the required criteria for severe weather and converge over a good chunk of Mississippi, extreme Southwest Tennessee, and Alabama. I don't think there will be a large tornado outbreak of any sort, but tornadoes could be possible in both the front-running supercells and main squall line.
Be sure to keep those NOAA weather alert radios in "alert" mode tomorrow if you live within the SPC's 15% or 30% risk areas. Even though this severe weather event will not break any records, it has the potential to affect a large population and cause damage.