Wednesday, February 22, 2012

2/22 - 3pm - Severe Storms Possible Tomorrow Across the South

Let's start with today first. It's unbelievably nice outside! You can't get much better than this in February in North Mississippi. You may be thinking that we'll have to pay for this great weather with some sort of severe weather event, and you're correct. This warm, moist air will serve as the fuel for a few severe storms across the region tomorrow night (see right for the SPC's latest Slight Risk area).

The main issue with the forecast at this point is where and exactly when will these storms form? The computer forecast models are having a difficult time figuring out if a warm layer of air aloft will serve to suppress storm development during the evening. This layer of air, which is called the "cap", is something that storm chasers in the Plains have to deal with quite often but usually not something we deal with here in the Southeast. Even though the models are having a hard time with this, we'll likely see a squall line of storms (QLCS in weather nerd lingo) roll through sometime around or after midnight tomorrow night. These will likely carry wind damage and hail threats, but the latest data coming in suggests that we may even see a couple isolated tornadoes. This will certainly not be a tornado outbreak by any means because the wind shear profiles for that kind of thing just aren't there. The energy helicity index (a combination of rotation in the atmosphere and instability) output on the left from the 18z NAM shows that this squall line will have some tornado ingredients to work with, but not all that much.

Another reason why we won't see a more significant severe weather risk is because the amount of moisture that we'll have filtering into the region from the Gulf won't be as strong as previously thought. Dewpoints just above 60 (on right) are certainly enough to trigger severe storms, but something closer to 70 is needed for more potent setups. Check out the video below for more details on this system:

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