Narkissos had the best answer, in my opinion as an atheist.
I affirm the following propositions:
1. There is no sound argument which should rationally lead one to conclude that probably a (generic) God exists versus no God existing.
2. There is no good personal reason to believe a particular God exists which isn't excluded by identical contrary claims of others. I think some personal experiences could be compelling, however an outsider must note that people with incompatible beliefs universally site the same evidence.
3. There are rational arguments which prove that certain concepts of God are impossible based on the common meaning of words. I would say an example of this is "incompatible properties arguments." I know Jehovah does not exist because no being could be fully just and fully merciful at the same time since, by definition, justice means corresponding merited punishment and mercy means less than the merited amount of punishment. At best, a being could be sometimes just and sometimes merciful.
I say I "know" certain conceptions of gods don't exist. I strongly doubt all others exist.
As an atheist I generally understand faith to mean "While I don't have all the evidence which would be required to convince others, I none-the-less believe something is true - and not probably true - for other reasons."
I've never found an atheist who believes he has inadequate reasons for his world view yet still actively hopes there are no gods.
Really, this ground is pretty well traveled and even the theistic philosophers have dropped this line of argument except when under severe rhetorical distress.
I would maintain to the OP that I don't believe anything can exist "outside nature." It seems to me that no meaningful linguistic statement can be made about such an entity and that any discussion about it could not possibly have content represented in reality.
Anyway, the argument is still a pile of crap:
P = God exists beyond nature
Q = Atheism is blind faith
P -> Q
if and only if
P2 = Disbelief in any hypothesis beyond nature is blind faith
Further, if we realize the following
P3 = There are many hypothesis with equivalent evidence for gods beyond nature.
P4 = The liklihood of any inidividual conclusion of an event beyond nature is reduced by the number the hypothesis in existance.
P5 = The disbelief in a particular hypothesis, Hn , is objectively more likely to be true than is the positive belief in that entity since
Hn / sum (Hi) will always be less than sumHi/Hn.
Since if no natural evidence can be brought to bear on a being which exists beyond nature then all such beings have an equal lielihood of existing.
C1 = Since sum(Hi) is very large, and given P3-P5, the atheist is justified in concluding that probably no God exists unless the theist can prove that the background probability of at least one God existing is very high. The theist cannot do this, therefore the conclusion of atheism is the best one.