Wtfo?

Yesterday was 75 and sunny, the perfect day to drive the Barracuda in to work. I usually avoid traffic like the plague, but on my way home I unexpectedly got stuck on an on-ramp that just wouldn't move. I know that I have some cooling issues and knew that I was in trouble. As usual the temperature started climbing and there was nothing I could do but just sit there and wait for it to overheat. My stock, in-dash gauge read right in the middle of the two thick white markers and my aftermarket gauge got all the way up to 230 degrees (not sure if this is accurate, I've never verified it). To make matters worse, there was a '68 Mustang about three cars behind me on the on-ramp that no doubt would have loved to point and laugh as he drove by while I'm stuck on the side of the road!

I had resigned myself to the fact that I was going to overheat and was just waiting for the steam to start pouring out from under my hood. This is where it gets weird: right at 232 degrees, the hottest I have EVER seen this engine get) the needle reversed and started going down. It went all the way back down to 212-215 or so and never got any hotter. Engine always stays right at 200 degrees on my aftermarket gauge during normal driving.

My cooling system:
23" x 18" x 2 1/4" aluminum, no name brand radiator (too small in my opinion)
14" 1500/2200cfm dual-stage electric fan (no belt-driven fan)
high-flow water pump with stock cast iron housing
Milodon 180 degree high-flow stat
catch-can plumbed as an overflow reservoir
NO hood seals, front or rear
NO fan shroud
Green coolant, no water wetter

Engine is a mostly stock 400, the only major modifications are uncoated, black painted headers, full MSD ignition, edelbrock 650 carb, and a mild cam.

Any ideas what could have caused the temp to go so high and then drop? Could the high pressure in the system possibly have dislodged some sort of restriction? Could the high temperature have cause an air bubble to pass through? I'm at a loss here....

If you need any more info about my combo feel free to ask. Would really love to figure this out.

Thanks!