Spring severe weather season well underway - another round on the way

April 14-16, 2011 will go down in the history books for the devastating tornado outbreaks that occurred over at least 17 states from Oklahoma and Kansas to Mississippi and Alabama to North Carolina.  Fortunately, the worst of the weather missed the Mid-South, though severe storms affected portions of the area Friday.  The map below, courtesy of The Weather Channel, shows the widespread nature of the tornado reports.  An interactive version of the map can be found here.

Plot of tornado reports on April 14-16, 2011, courtesy TWC

According to TWC, there were (preliminarily) 29 tornado reports on the 14th, 73 on the 15th, and 51 on the 16th, for a total of 153.  The average month of April has 163!  Compared to previous "outbreaks," the Super Tuesday outbreak on Feb. 5, 2008 (when Hickory Hill and portions of northern Shelby County were struck) had 86 tornadoes and 57 deaths.  May 29-31, 2004 had 170 tornadoes and 3 deaths, and the "Super Outbreak" (widely considered the worst tornado outbreak in U.S. history) had 147 tornadoes and 309 deaths.  According to Storm Prediction Center statistics, the preliminary number of tornadoes for the month of April stands at 371.  Our thoughts and condolences go out to all of those who were affected directly or indirectly by the past week's storms.

Unfortunately, there is no respite from the changing seasons, in which warm springtime airmasses collide with lingering winter airmasses, causing a battle that rages in the atmosphere above us.  The upcoming week is forecast to be a stormy one with several chances of rain and thunderstorms for much of the eastern half of the nation.  The map below shows the total precipitation forecast through Saturday morning from the NWS.  3-5" of rain is expected from the Mid-Mississippi Valley into the Ohio Valley, while the metro area is in an area forecast to see 2-3" of rain this week.

In the Mid-South, we'll see a small chance of thunderstorms late this afternoon through the night as a disturbance moves by to our north along a warm front that is moving north through the area today. The atmosphere will remain unstable Tuesday, but will be capped by warmer air aloft that should keep storms from forming most of the day.  It will certainly be very warm (mid 80s), humid and windy (gusts to 30-40 mph) though as the next major storm system approaches. 

Tuesday is when that storm system, which will be centered to our north, triggers the next potential severe weather outbreak, which will continue into the overnight hours Tuesday night.  A Moderate Risk of severe weather is in place for the Mid-Mississippi and Ohio River Valleys (extending as far south as NE AR and NW TN), while a Slight Risk is in place for the Memphis metro area.  See the risk area in the map below.  I expect a line of strong to severe thunderstorms to move through the region on a cold front late Tuesday night, after midnight, through early Wednesday.


Tuesday-Tuesday night severe weather risk area

We'll have continuing chances of thunderstorms right through the extended period, focused on times when fronts are nearby. These times are still somewhat uncertain, though we will keep you updated with the latest information.
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