Tonight's Mega Millions jackpot, already the fifth largest ever, is getting bigger.

Buoyed by strong ticket sales, lottery officials boosted the jackpot to $425 million from $400 million Friday morning, about 12 hours ahead of the 11 p.m. drawing. A lump sump, post-tax payout is worth about $161 million.

The jackpot was raised after sales were projected to rise about 40% by Friday evening, says Paula Otto, head of the Virginia lottery and lead director of the Multi State Lottery Association,

Chances of selecting the winning six-number ticket are just 1 in 259 million, but hopefuls aren't thwarted by the odds or suspicious of a Friday the 13th drawing. Ticket sales in Virginia were running nearly 600% above normal sales, while in Oregon, they were up almost 400%, lottery officials said.

"As a rule, things will really take off the day of the drawing,'' says Oregon state lottery spokesman Chuck Baumann.

The jackpot has been growing since Oct.1, with 20 straight drawings failing to hit a winner.

Forty-seven-year-old Scott Byerly, of Ankeny, Iowa, doesn't expect he'll have to solve the happy problem - or win - but says he's "buying the tickets to daydream."

If there's no winner tonight, Tuesday's drawing could rise to $550 million, Otto says.

Mega Millions record $656 million jackpot was split between three ticket holders in March 2012. A record Powerball jackpot, worth $590.5 million, was won by Floridian Gloria MacKenzie in May.

Contributing: Associated Press