Why leave it sit...go ahead and pitch your yeast now, then add the water once you've got it ready (assuming you're just talking a couple of hours). If you're taking a gravity reading take it now and adjust for the missing gallon.
[/I] Up Next - Hobgoblin
After That - Czech Pilsner
Primary - Humboldt Hop Rod (4/24)
Primary - NOT Wheat AG SNCA (5/5)
Conditioning - SNCA Clone (3/3),