GL: Best time to Leave for going upstream

[Tom Felice]

First I want to thank everyone who replies and gives me such good answers.  Your answers regarding how swift the current is on the Mississippi certainly gave me pause.  

My question now is:  I am considering (not enthusiastically) going at the end of winter but before a thaw.  Will that be the best time for slower current?  Do I have any hazards particular to that time of year? Ice? etc.  And what is the latest I could leave from the Land Between the Lakes area and still be "reasonably" certain I won't be in the spring flood current?  That's it, what say you.