Friday, Feb.24, 2017 Noon
A strong storm forming between St. Louis and Chicago will intensify rapidly during the day as it moves quickly northeast into Michigan. North and west of the storm track heavy snow is likely. However, the “warm sector” south and east of the storm will remain dry most of the day as we wait for a supply of moisture to arrive from the south. Once the moisture gets north, the strong dynamics of the parent storm should have no problem producing some severe thunderstorms. Primary threat will be strong winds. Hail is a slight risk while tornado chance is pretty close to zero.
This system is similar to the last time severe weather was widely advertised, but failed to show up. The problem is with the moisture. The dynamics with the system are tremendous, but the thermodynamics are quite weak. So, once again, the various models are relatively low on the “probability” of storm formation, but the so-called “conditional probability” for severe storms is high. What that means in normal people-speak is that the overall chance for a thunderstorm hitting you is small (about 30%). But IF a thunderstorm forms, there is a high chance it’ll reach severe levels (about 50%). So, if you multiply the two numbers you get a roughly 15% chance for severe winds within 25 miles of your home tonight. Obviously, the chance at any single point (your home) is much lower.
The models agree well on timing. The arrival of the cold front trailing the surface storm and sufficient moisture to generate thunderstorms should be about the same time. Best timing for Louisville looks like between 8 and 10 P.M. While some storms should form west of Louisville earlier, this system shouldn’t get well organized until it gets east of I-65. Areas east of Louisville have a greater chance for wind damage than we do. Best chance looks like 9 P.M. until Midnight for areas east of I-65.
As always, you’ll be hearing a lot of hype about storm potential this afternoon/evening. What you’ll be hearing will be “the worst case scenario.” Luckily, nature rarely reaches our hyped up expectations.