THE weather forecast for Tuesday isn't brilliant.

It looks like the TV satellite vans crowding around Pacific Quay will be beaming grey and moody shots of the Clyde to the world's rolling news channels, rather than the sunny, uplifting scenes Alex Salmond might have hoped for, in the final few minutes before he gets to his feet in the Imax cinema at Glasgow Science Centre.

A bit of drizzle, though, won't dampen the mood. The Scottish Goverment's white paper on independence, the blueprint for how the new state would be made to work and thrive, will be launched amid a blaze of publicity and, for Nationalists who have campaigned for this moment all their lives, genuine pride and celebration.

At 10.05am or so, right after the headlines, the news channels will cut live to the First Minister, who will set out his plan. There will be a real sense of occasion to the day. Mr Salmond is too good a showman to miss the opportunity. But it's his plan, his specific policies to grow the economy and create a fairer country that we are waiting to see. "We will be zeroing down to the SNP's choices," the First Minister promised on Tuesday. Those choices will be the most closely scrutinised section of the white paper.

The need for detail follows two reports this week which, though widely misunderstood, have framed the debate which will follow next week's launch.

On Monday the Institute for Fiscal Studies warned that an independent Scotland would have to impose bigger tax rises or deeper spending cuts than the rest of the UK to bring its debts down to a manageable level over the next 50 years. The point wasn't that an independent Scotland would be doomed by 2062, as some tried to suggest, it was that the country, faced with a faster-ageing population and declining oil revenues, would face slightly tougher challenges than the rest of the UK.

The following day the First Minister and Finance Secretary unveiled a Scottish Government report on the economics of independence. This was not, as some tried to suggest, a plan to create 200,000 jobs. Rather, it was an analysis of the problems facing Scotland and an appreciation they could be tackled in a variety of ways using the economic powers (or "levers" as you are probably fed up of hearing them described) of an independent country. It did not say which levers the SNP wished to pull, or how hard.

Unveiling the document at Dundee University, Mr Salmond insisted that extra tax rises or spending cuts would not be required. Instead he spoke of boosting the population, increasing productivity, getting more women into work, doubling exports and reviving Scotland's traditional engineering industry as well as nurturing new sectors such as life sciences. He returned to the theme at First Minister's Question on Thursday when he deftly harnessed the IFS report to his own cause. "What happens over the next 50 years will depend on the policies pursued in this country," he told MSPs, "and that in turn will depend on whether we have got control of the policies pursued in the country. I say let's get control of these economic levers, let's grow the Scottish economy and move forward to that better future."

How he actually plans to do all this we will learn on Tuesday.

The White Paper will stress that the SNP are but one political party among several. The statement at the heart of the Yes campaign - that decision about Scotland are best taken by those who live and work in Scotland - will be front and centre. There will be discussion of the "democratic deficit" and we will be reminded that the whole point of independence is the chance to choose different political paths.

When the blueprint is published, however, some hard-nosed political realities will take over. If Scots vote Yes it will be SNP which negotiates the country's exit from the UK, deciding the currency and other fundamental issues at least into the medium term. It's also a near-certainty that the SNP - currently 28 seats ahead of their nearest rivals, remember - would go on to lead the next administration in 2016. Alex Salmond could be First Minister until 2020. His plans are all-important.