I would make the biga with only a quarter-to-half of the yeast (depending on
temp) cover and leave in a cool-ish place (not in the fridge). Then add the
remainder of the yeast when you add the other ingredients in the morning.
I've found breads that have had the pre-ferment refrigerated don't seem to
rise quite as well for me (~85%) and taste a little different, a little
bitter. <shrug> Try it both ways. :-)
Best,
--
Shaun.
"Humans will have advanced a long, long, way when religious belief has a
cozy little classification in the DSM."
David Melville (in r.a.s.f1)