The 27 April tornado outbreak is noteworthy in many respects:
a) By many metrics, this outbreak appears to be the most significant in the U.S. over the past 60 years, even eclipsing the “Jumbo Outbreak” on 3-4 April 1974.
b) A large fraction of the storms produced tornadoes
c) A relatively large fraction of the tornados produced violent (EF3-EF5) tornadoes.
d) Many tornadoes were large and produced significant damage over long and wide tracks.
e) Tornadoes were so numerous and concentrated such that some paths overlapped (i.e., several areas experienced two, or even 3 tornadoes).
f) Sadly, a large number of fatalities occurred.
Over northern Alabama four distinct classes of storms produced tornadoes:
g) An early morning squall line (with an impressive embedded mesoscale convective vortex) produced tornadoes from central AL to TN.
h) A midmorning isolated supercell evolved in an airmass that was stable at low levels. It produced large hail (golf ball size) and one tornado.
i) A midday quasi-linear MCS produced numerous tornadoes over northern AL
j) Late afternoon storms generally produced the most intense tornadoes over Alabama and adjacent states.

We will present a synoptic overview that will detail the large values of upright buoyant instability and vertical wind shear, which produced conditions highly favorable for large, strong tornadoes. We will also review the sequence of events that affected Madison County and adjacent areas. Finally, we will summarize the characteristics of a subset of the noteworthy (EF4-EF5) tornadoes in the Huntsville to Birmingham corridor.