If that ole ‘in like a lion out like a lamb’ thing carries any weight, then what does it say about the middle of the month? Because next week, on St. Patrick’s Day, the Gulf Coast may be facing the potential for severe weather.
The data is still pretty preliminary and in the early stages, but there is enough consistency between the guidance to start to get an idea about what may be possible.
Data time
The most interesting part of this setup is how much is resembles a “southern plains” setup rather than a “Dixie Alley” setup. While we are limited to the Euro and GFS at this point (and their ensembles), it does still allow for a robust repository of information.
Perhaps not that robust.
Let’s start with the operational ECMWF compute weather model looking up at 300mb and 850mb because this is the foundation for this severe weather event.
Take a look at a few features on both of these maps. The donut hole near Kansas City is the area of low pressure. It looks like it is tilted to the northwest aloft. The fetch of wind in the low levels 850mb) is from deep in the Gulf and the NW Caribbean. And the upper-level winds are southwest over the region.
You can see that we have a SW flow aloft at 300mb with a Jet Streak back across parts of west Texas at the time of the model data (7pm on Wednesday night) as well as the moist air in place across parts of Louisiana, Mississippi and Alabama. Ahead of that Jet Streak, as it pivots to the northeast, there will be an increase push of low-level moisture as well as a slight bending of the wind to have more of a southerly – rather than southwesterly – flow.
This background setup is one that is conducive for the development of severe weather across the region. With no other information needed, I can confidently say that there will be the potential (though, not a guarantee) for severe weather somewhere in the region (Louisiana, Mississippi, Alabama) on Wednesday with just these two maps.
Between those two layers there will also be some instability.
This lends further credence to the potential for severe weather.
Over on the operation GFS computer weather model, data show a robust environment for severe weather, too.
I don’t often discuss lapse rates on my posts because you can get into the weeds pretty quickly. But, in this case, it highlights how unusual this setup is for Dixie Alley. Often, for severe weather in the region, a Lapse Rate of ‘greater than 5.8’ but rarely more than “6.5”is needed and a Supercell Composite of greater than “1” but lower than “6.”
In this case, we have the latter, almost dead on with most of the region between “1” and “6” but with Lapse Rate the numbers are from 6.5 to 7.5. This suggests that hail may be more of a concern than usual.
That suspicion is confirmed when you look at the sounding data from a random point.
This may be tough to see on that image, but in the “Sounding analogs” area, the top analog is for greater than 4″ hail from the Jackson, MS area.
That is softball-sized hail.
Does that mean softball-sized hail will happen? No. Does that mean softball-sized hail is likely? No. Does that mean softball-sized hail could happen? I suppose.
I think what this suggests more than anything else is that hail will be a concern more on Wednesday than it usually is on any regular storm day.
Other data
I ran the Karrie Meter to pull data for the region. As always, a big thanks to Dr. Kim Wood up at Mississippi State for helping create the Karrie Meter Map.
That is pulled from yesterday’s data, but there was not much of a change from yesterday to today, so this map is still pretty applicable. While the highest totals are off-shore, there is still a healthy blob of 4s in Louisiana, Mississippi and Alabama.
For those that are new to the Karrie Meter, there is a neat coincidence that falls out of the data. The numbers on the KM scale can convert back to a the SPC scale by simply dividing them in half. So numbers in the 4s and 5s convert back to a “Slight Risk” for severe weather.
So far, the SPC has not highlighted any area with a Slight Risk, but it would not surprise me if they do introduce one at some point this weekend.
Severe weather threats
This one is tricky to nail down this far out. But the data supports the potential for heavy rain, frequent lightning, wind gusts exceeding 55mph, hail up to the size of tennis balls (perhaps larger), and tornadoes cannot be ruled out at this point.On top of that, a strong tornado (EF2 or EF3) cannot be ruled out, either.
A lot like I said on TV last night, just because something cannot be “ruled out” doesn’t mean that it is “ruled in” either. It is important to remember that we are still working with early and incomplete data. Once we get closer we will be able to hone in on the potentials and specifics much better.
The Bottom Line
If you are making plans next week, make sure those plans include keeping tabs on the forecast. Make sure you have a NOAA Weather Radio handy and an app on your phone next Wednesday so you can be alerted to any potential severe weather. And if you are going to be outdoors (Spring Break camping) it is very, very important that you keep tabs on the weather and have a place to seek shelter.
We will know more as we move through the weekend and into next week. Please check back for updates on the forecast.
