March/April weather systems can be very dynamic with very strong kinematic fields/winds aloft. The instability is usually the make-or-break factor with these type of systems as the warm sector is prone to being socked in with crap clouds/convection (yes that's the technical term
) or the Gulf has recently been scoured and can only provide marginal to moderate dewpoints.
If the instability is not sufficient to sustain updrafts through the extreme shear, only the strong forcing right on the dryline can overcome the cap and the result is a huge, fast moving squall line that is usually not very photogenic but can produce widespread damaging winds/sometimes embedded tornadoes. Classic recent examples include April 6, 2001 and March 4, 2004.
If the instability is enough for sustained strong updrafts and T/Td spreads are small enough for sufficiently low cloud bases...watch out! There are many examples of infamous outbreaks of violent, killer tornadoes in April and sometimes March.
4/11/65 (IL, IN, OH)
4/3/74 (Super Outbreak, IN, OH, KY, TN, MS, AL, several others)
3/13/90 (OK, KS, NE, IA, IL)
4/26/91 (OK, KS, NE)
3/27/94 (AL, GA, SC)
4/19/96 (IL, IN)
4/8/98 (GA)
4/16/98 (TN)
4/8/99 (NE, IA, MO, IL, OH)
4/20/04 (IL, IN)
To name a few
Note: These situations may not be ideal for chasing because the extreme dynamics/wind fields make for fast moving storms.