Could be:
Condensation in your exhaust system, hot gasses and cold air make your tail pipe blow some white smoke [sometime at first start and rev you see a little water coming out of tail pipe] - normal in this weather.
OR
Head Gasket going, check your water, has it dropped, probally not a lot yet, so mark it and watch it, if you have access to a compresion tester, test it. - this could be a small head leak which forces water into cylinder on initial acceleration, which is then burnt = white smoke, if this is the reason you may get away with a coolant sealer for a while as water and cats don't really mix, but do beware if you sel it, it will not last and will fail big time when it goes, I did it, sealed for around 3 months the failed, which gave me water runing out of my exhaust when engine runing, I was trying to get in past the bad weather so I could repair it on my drive, left it to long.
OR
An outside guess, a lean mixture, perhaps an engine managment sensor not quite working fully. - this I rather doubt!
A generalisation of smoke.
White - Water or lean mixture
Black - Over rich mixture
Blue - oil