re: Preliminary Ratings: Lacombe Tornado - EF1; NOLA/Arabi Tornado - EF3

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Meteorologist Nick Mikulas
Model timing has shifted a bit, but our severe threat might end up being more robust because of this. A significant, areawide severe threat will overspread the area starting late Monday night or early Tuesday, here’s how I see it unfolding.

SPC has introduced a moderate, level 4 of 5 risk for severe storms over part of the area in their day 3 forecast, with most of the area at least in a level 3 of 5 risk between late Monday night and Tuesday. A day 3 moderate risk is quite rare, and has been issued because of pretty much maxed out severe parameters. These even look more impressive because the system has slowed a bit, meaning the peak time for action is now Tuesday morning into Tuesday afternoon. There could still be some isolated severe storms, especially northwest of a Leesville to Winnfield line Monday night, but I think the nighttime hours probably stay fairly tame east of that line. It’s not an exact representation, but a close enough forecast. Don’t draw a line and think that if you are two miles east of it that it’s impossible to see a storm Monday night. As these storms develop to our northwest, the main upper level feature will slow down as the jet stream aligns with the approaching front. This means training thunderstorms, and flooding rain. The most likely area, for the worst of this will be across northwest Louisiana, where a stripe of 4-8 inches of rain, centered near Shreveport looks likely.

Tuesday morning, storms will be blasting away to our northwest, but will start to inch this way. The big question is, will we get supercells ahead of the main line? If we do, all modes of severe weather will be likely with any of these storms, and there is a potential for strong tornadoes. Once the main line arrives by early afternoon, it will bring strong wind, and the threat for isolated tornadoes embedded within the line, but the most significant severe threat will come with any cells that can develop ahead of that solid line of storms that’ll move through. The most likely time for supercells will be from 10:00 AM until 4:00 PM. The earlier potential will be near the Texas border, and the later afternoon storms will be near the Mississippi River. The squall line will be just behind this, and should move through the area between noon and 6:00 PM. Locally, I expect 2-4 inches of rain. I think the worst of the flooding rain stays to our northwest, but it’s something to watch. WPC has most of the area in a slight to moderate risk for excessive rainfall, so that’ll be another layer to deal with in this system. Behind the front, we go back to pleasant weather, and don’t have any weather issues to deal with for at least 4-5 days.

I’m bringing out all the scary words in this one. Strong tornadoes, significant threat, moderate risk, and maxed out severe parameters all show up in this forecast. There are always failure options when it comes to severe weather. Cooler shelf waters in the Gulf could temper things a bit down south. Too many storms because of the strong upper level feature could interrupt the potentially volatile environment for severe weather. But you really need to be prepared for the chance that things come together, and we have a severe weather outbreak in our area. Severe parameters like this are rare, and we haven’t seen a high end threat like this in a while. I think there will be tornadoes in the state, and likely a couple in our area. It’s impossible to say exactly where, but I’ll be on top of things as this all unfolds. The “good” news is that this should be mainly a daytime threat in our area, so most will be awake, with the option to act quickly if needed. I’ll be watching incredibly closely, and keep you as informed as I am.

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This a daylight event for SELA?

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That's a mean motor scooter, and a bad go-getter. Houston north suburban is under the gun Monday night--early Tuesday morning, and they're talking bout catastrophic flooding, hail, even a major tornado (EF-3 or bigger--very rare in this area).

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Those low level lapse rates are pretty damn steep (for the region, not for the world).

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