Its all very well copying a list of actual weather reports for a station to try to justify the forecast(TAF). What one needs to remember is that significant changes in the current weather conditions i.e special reports (if they are being done as required!) are not broadcast outside of the aerodrome and on bulletins. The fact that 4000m was experienced on one METAR does not mean that these conditions didnt materialize frequently or infrequently between routine observations!
