The weather has been pretty comfortable for the past couple of weeks, but fall is a tricky season in the southern and central United States. We typically think of severe weather outbreaks as a problem in the spring, but thunderstorms can hit you just as hard in the autumn. A multi-day severe thunderstorm event is likely across parts of the south on Wednesday and Thursday, including storms that could rumble through around the time that kids are out trick-or-treating.
A sharp upper-level trough moving out of the Rocky Mountains on Wednesday will lead to the development of a low-pressure system over the south-central United States. Severe thunderstorms are possible on Wednesday and Thursday in the warm, unstable air to the southeast of the center of low pressure.
The severe threat will develop in central Texas during the day on Wednesday and progress east through the evening and overnight hours. The forecast from the Storm Prediction Center (SPC) early Wednesday morning painted much of eastern Texas and Louisiana under an enhanced risk, which is a three out of five on the scale used to measure the threat for severe weather. A slight risk for severe weather, a two out of five, stretches from central Texas through Mississippi. Wednesday’s forecast map is shown at the top of this article.
The risk for large hail and tornadoes is greatest in discrete thunderstorms that form in the unstable airmass ahead of the line of thunderstorms along the cold front. Some of the tornadoes could be on the stronger side, according to the SPC, especially in northern and central Louisiana. Damaging straight-line winds will be the greatest threat with the line or lines of thunderstorms that develop.
It’s possible that severe thunderstorms will disrupt communities as kids are out trick-or-treating. If you have kids in Texas or Louisiana who plan on going out tonight, keep a close eye on weather radar and listen up for watches or warnings. Make sure you have a safe place to go if severe weather approaches when you’re outside and away from home.
The active weather will shift east as the low-pressure system moves into the Mid-South on Thursday. The greatest threat on Thursday will likely be damaging straight-line winds in any lines of storms that can tap into strong wind shear. However, the SPC noted on Tuesday that “a tornado or two” is possible in storms that form along and near the northern Gulf Coast around New Orleans and Mobile.
It’s common to see severe thunderstorm events in the fall months as powerful cold fronts scour into the warm and humid air flowing north from the Gulf of Mexico. The latter half of fall is commonly referred to by meteorologists as the “second severe weather season” because of the uptick in damaging thunderstorms in parts of the southern United States as strong storm systems traverse the country. No matter how cold or calm it gets during the fall or winter, severe thunderstorms—including damaging winds, large hail, and tornadoes—can happen at any point in the fall or winter months if the right ingredients come together.
Severe weather reports to the Storm Prediction Center show occasional severe weather outbreaks on Halloween over the past ten years. The most prolific Halloween outbreak in recent years occurred in 2013, accounting for the majority of severe weather reports on the above map. In addition to more than 150 damaging wind reports from Louisiana to Ohio, the National Weather Service found that 17 tornadoes touched down along a relatively short path between Cape Girardeau, Missouri, and Paducah, Kentucky. Thankfully, despite the numerous tornadoes, the agency receiving no reports of injuries or fatalities during the event.