As I write this about 3:00 Saturday afternoon, our weather has been pretty quiet so far today. Early this morning there was a cluster of strong storms that moved across North/Central Mississippi and Central Alabama, but most of us were spared from that. Otherwise today has been overcast with a few peaks of sun, but the threat for severe weather still exists. Our Southern and Eastern Counties are under a Severe Thunderstorm Watch until 8:00 PM tonight for convection associated with the warm front moving Northward, and we have seen a few storms with hail over Jones and Wayne Counties.
ATMOSPHERIC SETUP: The National Weather Service in Jackson sent up a special weather balloon at 1:00 PM this afternoon to get a better handle on what conditions were like. It showed that the cap just above the surface (a layer of warm temperatures aloft) has begun eroding. There is plenty of CAPE (Convective Available Potential Energy), making our atmosphere moderately to very unstable. We haven't really seen storms yet because there hasn't been a forcing mechanism to lift air parcels from the ground into the atmosphere where they can tap into that energy. That's going to change as the low pressure system continues moving Eastward over Louisiana over the next few hours. The warm front is currently stationed near the Highway 84 Corridor, but is continuing to move Northward, as our temperatures and dewpoints have begun to really increase over the past couple of hours. The forcing from the low, and warmer temperatures and dewpoints will put us in a decent severe weather setup later on tonight.
THREATS: The biggest threat with this system is going to be large hail like we saw on Monday. Most of the energy for storms to tap into is aloft, and the atmosphere is cooling down rapidly as you increase in elevation, making for a perfect place to grown hail. Gusty winds could also be a problem if we see faster wind speeds develop aloft (as expected) that can mix down to the surface in the stronger thunderstorms. The tornado threat is not zero. Tornadoes come from surface-based storms. If all goes according to forecast, then our surface conditions will be right on the edge of favoring tornadoes, so we'll have to keep a watch on any supercells that form. In short, all modes of severe weather will be possible.
TIMING: Most forecast models (including our in-house model, the BAMS) shows most of the heavier activity holding off until after sunset. I think that our time window really looks to be from about 7:00 PM to 2:00 AM. Of course it won't storm everywhere during all of that time, but our atmosphere will be ripe during that period.
WHAT TO DO: As I always stress, the number one thing you should do is have a way to get warnings. The best methods are a NOAA Weather Radio or location-based smartphone app. Especially since it looks like this will hit while most people are asleep, make sure you have something that will wake you up. Never rely on outdoor tornado sirens!
We'll be here watching it and posting updates to the web. The crawl system on WTOK will also be up for any watches or warnings that are issued, and we'll break in to programming if necessary.