PROB 30 can be disregarded for use as an ETOPS adequate preflight under some operators rules
I keep raising it, but I believe the forecasts went from PROB30 fog to below minima fog in one step. And I suspect that change was AFTER the fog had formed.
Frankly, if when can't get better weather information than this 1 hour ahead of time, then the issue of fuel reserves is just academic.
The things to focus on are getting first world weather forecasting and first world air navigation facilities rather than trying to compensate with additional fuel & sheer piloting skills.