The AccuWeather forecast for Des Moines (central), Omaha (west) and Davenport (east) currently has the entire state clear and cold (but not unusually so--around the low 20s) on Thursday night.
That's basically good news for Hillary, who is counting on old ladies liable to be scared off by inclement weather (guess they won't need those snow-shovelers after all). And it's bad for John Edwards, who has the most committed supporters, a male-dominated pool of determined caucus-goers likely to brave the elements if neccessary.
It's probably good for Obama, who is also relying on lots of first-time caucus goers, including lots of young
voters people (although it's hard to say whether you could expect young people to be undaunted by ba weather or to say, 'Screw it, let's just stay home and watch Superbad.')
Update: Re-reading my item I noticedmy use of the word "voters" above and remembered that it's verboten. Or so say caucus purists. This weekend I saw an Iowa politico reprimand a reporter who referred to "voters," because caucusing--which involves forming groups whose numbers then translate into delegates via a complicated mathematical formula--isn't really "voting." Although I'm sure I'll make the mistake again before this thing is over.