Storms Return Friday

'Tis the season for severe weather in Mississippi. We are now in what is typically the peak of our spring severe weather season. There won't be any shortage of storms on Friday as our next weather system has the potential to be quite potent. This may be our "big" event of the year. In fact, I am so concerned about it, I have postponed my scheduled vacation (I was supposed to leave today) so that I can be here to help with severe weather coverage on Friday.

The Storm Prediction Center has put much Mississippi in a slight risk of severe storms. I fully expect parts of the area to be upgraded to a moderate risk in their Thursday update. Friday's system, in my opinion, could end up being the first high risk event of 2011. We had a high risk of severe weather on April 24, 2010, the day of the long track Yazoo City tornado. That's not to say we'll have a 150 mile tracking tornado on Friday, but it could still be pretty nasty for some areas. If not us, then close by.

Click the graphic below to see the current severe weather probabilities. Note the hatched area along and east of the I-55 corridor.

The rest of the maps below are from the NAM model and are for early Friday afternoon. 

This first map shows storms developing across Mississippi. The main upper level system stays well to our northwest back over Kansas and Missouri.

The next two maps are surface temperatures and surface dew points (moisture). We'll easily have temperatures well into the 70s, if not some 80s on Friday.

This data suggests dew points will be in the mid to upper 60s....more than enough juice to have severe storms.

This next map shows the winds at about 30,000 feet above the surface. The purple colors are the strongest winds. This data shows that those strong to our west early Friday afternoon may help to strengthen the storm system as those winds spread out over Mississippi.

This final map plots the forecast EHI or Energy Helicity Index. This is a good indicator of tornado potential as it combines CAPE (instability) with helicity (a combination of low-level wind shear and wind blowing into that shear). Note the yellows and orange colors in areas east of I-55. This is where my eye brows raise and it indicates a possibility of strong tornadoes IF this model data is correct. 

RARELY do severe weather set-ups work out exactly how models forecast. The system is just beginning to come ashore on the west coast now and it will soon be in the range of the upper air network. That is to say the weather balloons that get released all across the country will be able to get data from the storm. This data will help the computer models (hopefully) come up with a more accurate forecast. 

There are a couple of things to watch out for. 1) Timing. This is key. Everything has to come together at the right time in order for there to be a big severe weather outbreak. 2) CAP - I've talked about this before. A cap is a layer of warmer air aloft that acts like a lid on a boiling pan of water. The lid keeps water from boiling over at first just as in the cap keeps air from being able to rise and storms from forming. Eventually the water in the pan will boil so hard and strong that it overcomes the lid and boils over. A similar thing applies in meteorology. Eventually the weather system will strengthen to the point it can overcome the cap - the atmosphere's lid - and volatile storms will form. There will be a cap on Friday. The question is does it break  early in the day so we see multiple rounds of storms? Or does it hang on most of Friday and we get only one round of storms or no storms at all? 

I'll post another discussion tomorrow as things become clearer. In the meantime, today's weather is outstanding. Get out and enjoy it! I'm going to go unpack...

Eric - elaw@wlbt.com