Piperboy,
Seems to me a little thread drift . . .
“do I really give amonkeys what the field is reporting, how would one determine from thetaf/metars what the "tops" of the mist or fog is”
In my opinion, yes you do give a “monkeys” - the field forecast is important to your planned alternate options. In the example, a report of fog is read as field un-available.
VFR on top. When on top of a cloud layer, a reasonable cloud base (say 1,000 ft) would give an opportunity for a forced landing. In this example fog would precludes uch a contingency. A radar service cannot give you an acceptable RVR (probably better to be vectored away from built-up areas).
(I assume nav does not require ground reference).
TheTAF-Metar gives the cloud layers to expect, reported as the bottom of the layer. Also any PROB forecast would give a trend i.e. is the fog expected to clearor getting worse?
On climb out from your clear departure field, the forward situation and any need to return should be apparent.
In the Maule, a few clear views of farmland would provide a contingency and goahead, whereas a fog blanket would probably press the return button, depending on the confidence of a clear destination and time of exposure.
I don’t see that IFR/ IR gives any additional options with this example (fog = RVR less than acceptable – assuming your Maule is not CAT3 equipped
).
flyme