The definition of marginal depends on the particular operator and what they define as maginal. Some use the wording that if the weather is right at alternate mins as derived by Opsecs then it is marginal. Other operators might define "marginal" as being within a certain vis/ceiling, like 100 ft/ 1/2 mile.kwalker said:I am still unclear on what a marginal condition would be for your 1st alternate though. If the wx is at or above the alternate minimums, then you can use it for an alternate. What could be a qualifier for the 1st alternate? Thanks.