Favourable departure weather with a worsening route
A private pilot is preparing a daytime VFR flight through terrain that becomes progressively higher toward the destination. The departure aerodrome reports good visibility and scattered cloud. A current destination observation also appears favourable. The route forecast, however, shows moisture moving into the intervening high terrain, and recent reports describe lowering cloud on the windward slopes. The passenger emphasizes that an appointment cannot be missed. The aircraft has no approval for the icing conditions that may be encountered in cloud, and the pilot plans to remain in visual conditions. Several lower-terrain diversion options are available early in the route, but options become more limited farther along the valley.
1. Why are the two aerodrome observations insufficient for the decision?
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They describe particular locations and times rather than every intervening terrain area. Route cloud, terrain clearance, forecast trends and actual reports must also be assessed. Good conditions at both ends do not establish a safe visual passage through the mountains.
2. What decision process best protects the available options?
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Set conservative route and turnaround criteria before departure, consider delay or a lower-risk route, and reassess actual conditions early. Do not allow the passenger’s appointment to replace weather limits. Divert or turn back while safe visual references and manoeuvring room remain.