The forecast for "Forces of Nature" is pleasantly bumpy.

Like the crazy weather it uses as a metaphor, this film -- part road movie and part romantic comedy -- is happily full of the unexpected.

Ben (Ben Affleck) and Sarah (Sandra Bullock) are the characters suffering through various disasters on planes, trains and automobiles on their way from New York to Savannah, Ga. After their plane wrecks on the runway as they try to take off, they end up stuck in a rental car with a guy named Vic, headed South.

Cautious Ben is on his way to get married, after an out-of-control bachelor party that prompts grandpa to have a heart attack and warn his grandson not to get hitched. It's not the only admonition Ben gets; almost everyone he meets has a word of caution about love and commitment. Even so, he sees evidence of happiness, too, and hope.

But Ben's feet are just cold enough for him to be attracted by free-spirited Sarah, who's a bit of a force of nature (though not the hurricane the ads might lead you to expect). She has a great capacity for joy but also an injured sense of self, and Bullock's girl-next-door sensibility actually works to give the character, who's more complicated than meets the eye, a touch of realistic vulnerability.

Affleck's presence is appropriately reserved as he stammers and hesitates, but he reveals an appealing strength of character as he figures out what to do. And he and Bullock build a credible chemistry as two strangers thrown together at the most important moments in their lives.

Best of all, they're funny, as they endure, with likable aplomb, the hailstones and hurricane thrown at them.

The supporting players are amusing, especially Steve Zahn as the spacey best man. A notable flaw, however, is that we don't see enough of Ben's fiancee (Maura Tierney of TV's "NewsRadio") to understand the depth of his love for her.

Still, the low-key pace of the film, directed with funky flair by Bronwen Hughes ("Harriet the Spy") from Marc Lawrence's script, works to make it an enjoyable, easy ride.

There may be storms along the way, but as in life, the sun isn't far behind.

'Forces of Nature'

Starring Ben Affleck and Sandra Bullock

Directed by Bronwen Hughes

Released by DreamWorks

Rated PG-13 (sensuality, language and a scene of drug use)

Running time: 106 minutes

Sun score: * * *

Pub Date: 3/19/99