We have been monitoring the potential for a severe weather outbreak on Wednesday since we were highlighted in a Day 4 outlook from the Storm Prediction Center. Things are finally starting to come together and we have a good idea on what we can expect.
This is the current outlook from the Storm Prediction Center for Wednesday (4/5)
As displayed above, areas along and east of I-65 have been highlighted in a Moderate Risk, indicating the highest potential for severe weather in that area. Let’s be clear, everyone will have a risk for severe weather on Wednesday but the highest probability for strong, long-tracked tornadoes will be across this area, in addition to very large hail and damaging winds.
As we take a look at hi-res model data, we go out as far as it can into Wednesday morning. We see storms forming across the Gulf Coast and moving in a southwest to northeast fashion.
Severe weather paramaters (SCP and STP) are lagging behind the storms with the initial round. The following images indicate where conditions are favorable for supercell/tornadic development.
Now we look over to the NAM model run and the paramets do ramp up after lunchtime. Below you will see SCP, STP and radar in that order
There remains to be uncertainty as to if the atmosphere will recover after the morning thunderstorms, if it will break the CAP (scenario 1), if it will take away instability (scenario 2), or it will leave us cloudy (scenario 3)
SCENARIO 1 (“most likely”)
All model data is currently hinting at this being the scenario to take place. Storms will exit northeast Alabama around lunchtime. Clouds will thin out, and instability will take place as temperatures warm (see images below):
In this scenario, dew points reach the mid 60’s and even peak to around 70F in some locations in the Moderate Risk area. This is great fuel for thunderstorms, and if they can tap into the instability/shear in place – tornadic development:
SCENARIO 2 (“could happen”)
The thunderstorms realize instability a little bit earlier and take the fuel out of the atmosphere. The afternoon storms don’t have much to feed off of. Thunderstorms still occur in the afternoon but are not quite as strong.
SCENARIO 3 (“not likely”)
Clouds overspread the area and leave instability in the atmosphere and not at the surface. Thunderstorms don’t reach high altitudes and never the CAP doesn’t break because of the clouds in place “protecting it”. This would cause thunderstorms to remain in the “general” stage.
BOTTOM LINE (TL;DR)
The potential is there for severe weather tomorrow. It’s very important to have a way to receive Watches and Warnings. At this time, I anticipate a Severe Thunderstorm Watch being issued for the mid-morning convection for central/northeast/east Alabama. Anything after that is anyone’s guess. All depends on what factors come into place.