Wasn't there talk about fertilizer, underground farms, and related agricultural improvements? Being able to mass-produce larger quantities of food year-round would make Leaf self-sufficient and be able to export food far more than normally, if nothing else.
Most of the trouble is going to be making the crops survive since it's winter, sadly; we'd need some form of sunlight + warmth to give the crops the energy they need to grow. Jiraiya had these Daybright seals, which I think mimic photosynthesis sufficiently [citation needed], but unless we want to have Akane spam EM every 3 hours, we need a source of warmth to keep the crops from breaking. Jiraiya's seals probably should have something, and if worst comes to worst we can just use a fire beneath the farm itself to warm the area or something.
Underground farms should be insulated from surface weather, and the deeper we dig, the warmer it is. So this is not a problem.