What weather conditions necessitate an alternate aerodrome when within 50NM from the departing aerodrome?

For flight planning, the requirement for an alternate aerodrome is typically dictated by the weather conditions at the destination aerodrome as well as en-route and departure aerodrome weather. In particular, when cloud cover is at or higher than scattered (SCT) with a base below 1,500 feet and visibility is less than 8 kilometers, it raises significant concerns for a pilot regarding safe landing conditions.

This scenario suggests reduced visibility and potentially low cloud ceilings which could impair visual flight operations and hinder maneuverability, especially during an approach and landing. The need for an alternate aerodrome becomes even more crucial under these circumstances as pilots need to ensure they have a viable option for landing should the primary destination weather conditions worsen or become unsuitable for landing.

Weather conditions such as clear skies or just thunderstorms do not automatically invoke the need for an alternate aerodrome under these specific circumstances, nor do fog or mist below 1,000 feet create the same level of concern regarding high-density traffic and cloud cover that might interfere with safe landing operations. Thus, the identified conditions warrant the necessity of an alternate for safety and compliance with aviation regulations.