[ame="http://www.youtube.com/watch?v=zcD77xT_n44&feature=related"]Hey, if Tiny could do it...[/ame]If you as a DM think that a rogue wearing shiny black leather couldn't possibly hide in the middle of a flat, barren, snow covered plain on a bright, sunny day without going prone, no matter what his skill bonus is, no matter what feats he has, then that is your perogative. I would never allow it, no matter what the rules may say. Rules can't overrule intelligence and just basic common sense. That's why there's a DM at all, so that insane rulings like that aren't allowed.
There have been endless arguments over the ability. e.g. " Can I drop a coin on the floor? It casts a shadow, after all, so...". The ability itself gives no stated guidelines, so a certain amount of common sense is needed. In the opinion of many, the shadow has to be big enough to hide in, even if you aren't actually in it. Now, we can refight those battles, but let's not.A shadow serves in this case. A shadow can be cast by setting your pack down on the floor.
There have been endless arguments over the ability. e.g. " Can I drop a coin on the floor? It casts a shadow, after all, so...". The ability itself gives no stated guidelines, so a certain amount of common sense is needed. In the opinion of many, the shadow has to be big enough to hide in, even if you aren't actually in it. Now, we can refight those battles, but let's not.
The question was, can you do it with no cover, if your skill is high enough. The answer by the book is no.
As you suggest, you may be able to create some concealment of some kind, but now you're begging the question rather than dealing with it.