We've all seen steam coming from boiling water on a stove.  Why is a
large "plume" of steam emmited when the heat is removed?

You can see this for yourself by conducting this experiment:
1. Place pot of water on gas burner turned on high. (Dont' cover pot).
2. Allow water to boil for a minute or so.
3. Observe steam.
4. Turn off burner or remove pot from burner.
5. Observe a lot more steam for about 2 seconds.

Hi chrisstankevitz and thanks for the question.

I too have observed this phenomenon and others have asked the same
question as you.  The best answer is given in an article in "New
Scientist" and here it is:

 
"Question 
I have noticed that the amount of steam arising from frying pans and
saucepans increases rapidly in the seconds just after I have turned
off the flame under the pan. Why is this?
  
Answer 
Steam is a completely colourless gas and cannot be seen at all. When
we refer to seeing steam, what we are actually seeing is the water
molecules condensing into tiny water droplets or water vapour. If you
watch a kettle boiling, there is the colourless steam at the exit of
the spout, with water vapour only being visible 1 or 2 centimetres
from the spout.

When the heat source is removed from a pan, the small decrease in the
temperature of its contents means that the steam is condensing to
water vapour much closer to the pan, so that the pan appears to be
emitting more "steam" (water vapour). In fact, less steam rises from a
pan once the heat is removed, but you see more water vapour in its
place, since water vapour is cooler than steam."
http://www.newscientist.com/lastword/answers/748home.jsp?tp=home1

Thank you for the question and if you found my answer helpful 
please do not hesitate to rate it, and if you have any doubts 
regarding my answer just ask for a clarification and I will be happy
to help.
 
THX1138 

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