It's meant to be GM1-CAT.OP.AH.180 Selection of aerodromes - aeroplanes APPLICATION OF AERODROME FORECASTS which you'll find on page 210 of the
CRD b.3 document that was published as part of the CRD. However, I believe that contains some errors if it's meant to be consistent with the old JAR-OPS1 IEM.
The AMC/GM will presumably be finalised as a Decision only when the Ops regulation is finally published.