The reference to "Almost certain" is simply that nothing to do with weather is ever certain.
And then we get to the difficult bit.
The weather during Mr. EIR's flight was pretty much as forecast. However, at his destination and for any airport within distance of the fuel he has remaining, the weather is OVC008.
Mr. EIR departed in all good faith having checked TAFs and METARs, but the weather stubbornly refused to co-operate and the front did not clear. He has not been trained to fly an instrument approach, and may not legally fly one. His aircraft is suitably equipped, having ILS, ADF, DME, Pitot heat etc.
But he hasn't been trained.
In 30 minutes or so his situation will rapidly become an emergency due to low fuel.
So, in order to save his life, he has (a) to break the law and fly outside the privileges of his licence and (b) fly a procedure for which he has received absolutely no training whatsoever. If he screws up the approach and has to go around, he will be straight back into the murk, already stressed and worried, will have to transfer back to instruments.
You estimate - what are his likely chances of survival?
Speaking for myself, I would far prefer him to be IMC rated. Otherwise we are sacrificing his life for bureaucracy.