"Phil Layton" wrote in message
...

LVPs come into force when the RVR is 600m or cloud ceiling 200ft or less.
That said, Traffic Managers do sometimes apply a regulation on the basis
of
a forecast :-) which can bring delays even if LVPs do not materialise.
Fog warnings per se are not really useful to us, as they do not recognise
the LVP criteria (as they are looking for a vis less than 1000m? but no
reference to cloud) and they often arrive after the fog has formed - but
we'll put that down to the AFTN :-)

Thanks for that, Phil. Airfield fog warnings are issued for a (met.)
visilbility of 600m or less and I would hope are normally issued well before
any fog materialises at the airfield, thus it's somewhat disappointing to
note they're not really useful to you. Certainly a warning should be out in
advance if fog is in the short TAF and on occasion a warning will be issued
when fog isn't in the TAF, i.e. the risk is considered significant but 30%.

Jon.