Gary,

Metar/TAF ceiling are always AGL not MSL. This is something that
we can easily forget. Few weeks ago, we were at KLEX early in the
morning when the ceiling was 600'. With the ILS Rwy 4 DH at 1170',
at first I thought the ceiling was below minimum and decided to wait.
After few hours, the ceiling was still at 600' but the cup of coffee
livened up my brain. I then realized that the DH AGL was 200' and the
ceiling was 600' AGL not MSL so it was a go for us.

Hai Longworth