According to Navy guidance, you will need an alternate airfield when weather is forecasted at less than _____' AGL ceiling and/or _____ SM of visibility.

Study for the METRO (Meteorology) – VT-10 Test. Enhance your knowledge with flashcards and multiple choice questions, each with hints and explanations. Get ready for your exam today!

The idea is to plan for a safe alternative when the weather at the destination isn’t good enough for a normal approach. Navy guidance uses specific minimums for when you must have an alternate airport lined up. If the forecasted conditions at the destination fall below 3000 feet of ceiling AGL or below 3 statute miles of visibility (or both), you’re required to designate an alternate airfield. The “and/or” means either condition being worse than the threshold triggers the need for an alternate.

So the threshold here is 3000 feet and 3 miles. If the forecasted weather is under either of those values, you must have an alternate. The other options set thresholds that are either too low (not providing sufficient planning margin) or too high (unnecessarily requiring alternates).