I'd happily argue that aviation forecasts obtained via the BOM would be perfectly acceptable-
Car Ramrod,
You would be free to happily or unhappily make that argument, but the probabilities, based on the precedents so far, are that you would wind up unhappy, regardless of the starting point.
There have been a number of CASA/CDDP prosecutions over the years, on this point, the courts have found that the law is quite clear and unambiguous, you must only use approved sources.
That there is some temporary problem does not "repeal" the law. Just delay/cancel the flight to comply.
Indeed niggling and silly points like this are like pilot log books, a happy hunting ground when "they" are determined to do you for something, when the major case failed.
In one case, quite some time ago ( so don't ask me for an AustLII reference) a pilot rang a flying school at his proposed destination and a poor sodding instructor gave him a rundown on what he could see out the window.
An entirely unrelated incident brought the matter to CASA 's attention.
Both the pilot who made the call, and the instructor who helped were prosecuted.
There were no actions as a result of the initiating incident, although the FOI wanted to, Canberra made it clear to said FOI that the actions of the pilot in command were well covered by the legal rights and obligations of the pilot in command.
Tootle pip!!