Severe Storms Early Wednesday?

The Storm Prediction Center (SPC) in Norman, OK has put western parts of the area in a Slight Risk for severe storms late Tuesday (first map). The highest probabilities for tornadoes, possibly strong, will be in two areas (second map). The first area to our west-northwest across much of Arkansas, and the second area to our south across Louisiana. This outlooks are valid from 6am Tuesday -6am Wednesday.

The SPC has also put much of our area in a Slight Risk for severe storms for Wednesday as well. See map below.

I'm not fully biting into the chances for severe weather just yet. To get thunderstorms and severe weather, there are three big things we look at. 1. Lift to help generate clouds and precipitation. 2. Wind shear (wind increasing in speed and changing direction with height) to help thunderstorm to rotate. 3. Instability to help fuel storms. Tuesday night and Wednesday we'll have numbers 1 and 2, but I'm not sure we'll have number 3 in place. Here is why:

Very dry air moved into our area following the system that brought rain to the area on Saturday. The map below shows that the best moisture (dewpoints) are well down into the Gulf of Mexico as evidence by the green colors on the map below.

With such very dry air in place, there is some question as to wheather or not sufficent moisture can return to our area in time for next storm system, and if it does, will it be enough to help fuel severe thunderstorms? The computer models disagree on this.

The next two maps are forecast instability for 6am Wednesday. The first map is the GFS model, the second map is the NAM model.

When you combine the areas of best instability with the best wind shear, you get the this:

So the bottom line is that we have two chances to watch for storms and severe weather. The first late Tuesday night and Wednesday morning, if storms that form to our west during the day Tuesday can hold together all night. If we don't have the instability in place to help sustain them, they will weaken and we'll end up with mostly heavy rain. If we are able to get severe weather, it would mainly be areas south of I-20. Damaging striaght-line winds, large hail and a couple of tornadoes would be possible.

We may have a second chance to see storms depending on the speed of the cold front. The GFS model is faster than the NAM. If the front slows down and comes through later on Wednesday, we may have a chance to warm-up and increase the instability across the area for the front to work with. By then the best winds will be moving away from us. If this happens though, damaging winds and hail would still be a threat.

We're still 36-48 hours away from this event and in the weather world that is a lot of time! The finer details of the forecast will be ironed out closer to the event, but you probably already know that sometimes we have to just constantly monitor the atmosphere to see how it is changing after the event starts. It is important to stay weather aware over the next couple of days, no matter where you live in Mississippi. Severe weather or not, we're likely going to see some good downpours. The GFS brings over an 1" of rain to the area with this system.

Be sure to check me out on Twitter as I'll be posting some more thoughts as we get closer to Tuesday night and Wednesday.

Eric - elaw@wlbt.com