Saturday, March 15, 2025

High Risk For Tornadoes and Severe Thunderstorms Today





 While we wait for a supercell thunderstorm with a history of producing a tornado to approach Northwest Alabama (probably Marion County, most likely spot for it to enter), the new Day 1 Outlook has been issued by SPC. And it expands the High Risk. This is just not the kind of severe weather outlook we like to see. This is relatively rare, and we in the Tennessee Valley are in the hot spot for what is shaping up to be a full-blown outbreak of tornadoes and severe thunderstorms. 


The Level 5 out of 5 High Risk includes Cullman, Blount, Morgan, Walker, Winston, Fayette, Lamar, Franklin, and Lawrence Counties in North Alabama. That carries a 30% chance of a tornado within 25 miles of any given point later today. The rest of North Alabama and Southern Middle Tennessee is under the Level 4 out of 5 Moderate Risk with a 15% chance of a tornado within 25 miles of any given point. Then as you go farther into Tennessee, that probability drops to 10%, which is still pretty significant. 

And the whole area is hatched. Today is a stay when stronger tornadoes capable of being particularly damaging are possible, some are likely to be rated E/F2-F3 or perhaps even higher in a few cases. This is setting up to be the worst tornado outbreak we've dealt with in several years. At this point we all just need to take any warnings seriously and do our best to keep each other safe through it. This is VERY SERIOUS BUSINESS.



These supercell thunderstorms today will also be capable of producing very large hail up to at least golfball size and damaging winds that could reach hurricane force. 

The storms are expected to be isolated and mostly come between Noon and Midnight, before a squall line finishes things off around Midnight. 

What we're dealing with overnight/into the early morning is just sort of a warm-up. The worst weather is expected Saturday afternoon, evening, and lasting into at least part of the night hours. It's best to assume the severe weather could ramp up again as early as Midday and might take as late as Midnight to start winding down. This is a high-impact, long-duration event with potential for multiple rounds of severe weather, the main concern being tornadoes. And some of them could do a lot of damage and be very dangerous, life-threatening situations. 

If you have a storm shelter or basement today, use it. 

Most people will be sheltering in a regular house or apartment during a Tornado Warnings. You need to get to the lowest floor, in a smaller room like a bathroom, closet, or hallway. And make sure that room does not have any windows, ideally it puts some walls between you and the outside. Cover your body as best you can, especially your head. Blankets are good, or a pillow, or even a small mattress. Or even get up under something sturdy like a desk, table, set of stairs, or a workbench. Often you find those in the basement level of a house or on the ground floor if there's more than one floor. So you can protect yourself in case of falling debris. And it's really best if you shelter with a safety helmet on; most people have a football or bike helmet around the house somewhere. They are more helpful for kids, but adults can also sometimes save their lives by wearing one. Most tornado deaths come from head and neck injuries. Even if someone's whole house ends up collapsing under the winds, sometimes a helmet will save the person's life. 

So everybody stay safe today, let's take care of each other. 

 SPC AC 150534

   Day 1 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   1234 AM CDT Sat Mar 15 2025


   Valid 151200Z - 161200Z


   ...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ALONG A CORRIDOR

   FROM CENTRAL MISSISSIPPI INTO NORTHERN/CENTRAL ALABAMA...


   ...SUMMARY...

   A tornado outbreak is expected across the central Gulf Coast States

   and Deep South into the Tennessee Valley. Numerous significant

   tornadoes, some of which should be long-track and potentially

   violent, are expected this afternoon and evening. The most dangerous

   tornado threat should begin across eastern Louisiana and Mississippi

   during the late morning to afternoon, spread across Alabama late day

   into the evening, and reach western parts of the Florida Panhandle

   and Georgia Saturday night.


   ...Central Gulf States/Tennessee Valley Region...


   Strong cyclone that is lifting northeast across the upper MS Valley

   will eject into northwest Ontario later today as a very strong

   mid-level speed max digs southeast across northern Mexico into

   south-central TX. Later tonight, this jet will translate into the

   central Gulf States with winds in excess of 110kt. In response to

   this feature, a surface low should evolve along the trailing

   boundary along the TX/LA border early in the period, then track

   northeast into western KY by 16/00z. Additionally, an intense LLJ

   will evolve by mid day across northern MS and strengthen during the

   afternoon as it gradually shifts downstream into AL/middle TN/KY by

   early evening. Net result should be for a bit higher moisture

   content to advance farther north than previous thought.


   Early this morning, an arcing band of scattered supercells extended

   across southern IL into eastern AR. More isolated activity has

   persisted much of the late evening across portions of MS. Latest

   thinking is convective overturning should remain minimal across the

   lower MS Valley and this will allow significant destabilization to

   materialize ahead of the surface low early in the period. Latest

   surface data depicts lower 70s dew points across southern

   LA/southwest MS, with mid 60s approaching the south side of the

   Memphis metro. Confidence is increasing that a corridor of strong

   buoyancy and intense shear will be in place prior to the

   aforementioned speed max/short-wave trough. Forecast soundings

   exhibit steep mid-level lapse rates with ESRH in excess of 500 m2/s2

   across a broad swath of the central Gulf States, especially the

   categorical High Risk delineation.


   While scattered strong/severe thunderstorms will likely be ongoing

   at the start of the period across the western TN Valley, convection

   should increase in intensity by late morning across LA as the

   leading edge of the approaching short wave begins to influence this

   region. Continued boundary-layer heating will lead to subsequent

   development and supercells should mature and race northeast as the

   flow strengthens. This flow regime favors long-lived tornadoes, and

   the parameter space suggests potentially violent, long-track

   tornadoes. This activity will grow upscale in both coverage and

   intensity through late afternoon as the overall severe complex

   shifts downstream. Large hail and damaging winds may also accompany

   these storms, but the primary concern today will be the likelihood

   for a tornado outbreak, especially across Mississippi into Alabama.


   ..Darrow/Moore.. 03/15/2025

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