The next 48 hours

…MAJOR SEVERE WEATHER OUTBREAK LIKELY OVER ALABAMA…

The official tally from the April 15 outbreak indicates that 41 tornadoes occurred in Alabama.  This major outbreak started in Oklahoma and Arkansas on April 14, and ended in North Carolina and Virginia on April 16. 

We are now facing another multi-day, significant tornado outbreak across the SE US.  A slow-moving upper-level trough will spin in the central US, and a front will move very slowly eastward.  Out ahead of the front, warm, moist air will flow in on southerly winds, with some of the highest humidity we’ve had this year.  Impulses will rotate around the trough, trigerring episodes of storms.  Early this morning, a line of storms was moving across northwest AL.  We expect this line to weaken this morning as it moves into more stable air in Alabama, but it still may produce damaging wind, mainly NW of BHM. 

This afternoon, especially if we get several hours of sunshine and temperatures warm into the lower 80s, the air will become unstable (CAPE up to 2,000 J/kg), and strong to severe thunderstorms may develop.  The key to their location may be where the morning storms stop/die off and where the sun comes out.  These factors will determine areas of instability and boundaries to focus storm development.  Wind shear will not be that strong today (helicity less than 200 m2/s2), so while tornadoes are possible, damaging winds, lightning, and hail are the main threats. 

The main system will start to move more by Wednesday, and it looks like a surface low pressure area will form along the front to our NW, but closeby (northern MS or TN).  As this occurs, wind shear will increase significantly on Wednesday (helicity 400-600 m2/s2).  The air will become very unstable again, with dewpoints approaching 70, temperatures in the 80s, and CAPE of 1,500 to 3,000 J/kg.  The combination of summerlike unstable air and winterlike wind shear will be a dangerous combination that may produce significant tornadoes over northern and central Alabama (mainly north of a line from Demopolis to Montgomery to Alex City), in addition to flooding rains and damaging winds.  The exact location of the largest threat is difficult to pinpoint at this time, since boundaries left by storms tomorrow, and areas of maximum sunshine, will force storms in some areas more than others.  But, if the computer models are right (and they have been consistent), the largest threat will be in northern MS and NW Alabama Wed morning, then from HSV to BHM Wed afternoon, and NE Alabama toward sunset. 

This is a serious situation.  Just because there have been a lot of severe weather outbreaks this year (similar to 1998), and you have heard a lot of tornado watches and warnings, don’t get complacent.  Tornadoes were all over the place just south of BHM Metro two Fridays ago, and this time it could include TCL, BHM, ANB, Cullman, GAD, HSV, and MSL.  Have a plan for what you will do in a tornado warning at work, at home, wherever you will be.  The schools mainly have tornado plans in place.  Keep an eye on the weather carefully through Wednesday night.

At work, in large buildings, interior hallways on the lowest floors and stairways are often best.  Stay away from windows and outside doors.  In smaller offices, go to the lowest floor, in an interior room, away from windows and doors. 

In the home, the underground part of a basement is best, but get under a work bench, heavy table, etc.  Stay away from garage doors!  They are a weak point on your house in winds.  If you don’t have a basement, go to the lowest floor, interior room or hallway, away from windows, doors, and outside walls.  Hall closets, if on interior walls, are good.  Protect your head.  Put batting helmets, football helmets, bicycle helmets on the kids.  Stay low.  Falling trees can come through the roof, but often stop before coming all the way through.

In mobile homes, leave.  All of the fatalities in April 15 tornadoes in Alabama were in mobile homes.  If an outbreak starts, try to go ahead and go to a sturdy building ahead of time and wait it out.  You are better off in a ditch than in a mobile home.

There is no reason to panic.  Just have a plan ready, follow the weather, and if a warning is issued, execute your plan. 

Another update around 11 am CDT.

Category: Severe Weather