FAA Part 107 Remote Pilot (UAG)OperationsMedium
A remote pilot in command reviews an early-morning weather briefing showing a surface temperature of 68°F and a dew point of 66°F, with the spread forecast to continue narrowing before sunrise. What weather hazard should the pilot most anticipate before launching?
- AIncreased density altitude reducing lift
- BMagnetic compass deviation errors
- CWind shear from an approaching thunderstorm
- DFog formation reducing surface visibility
Show answer & explanationAnswer & explanation
Correct answer: D. Fog formation reducing surface visibility
A narrow and closing temperature/dew point spread (here 2°F) indicates the air is near saturation, which strongly favors fog formation, especially overnight when temperatures continue to fall toward the dew point.
Why the other options are wrong
- A. Density altitude relates to temperature/pressure/altitude, not dew point spread.
- B. Compass deviation is unrelated to temperature/dew point data.
- C. Wind shear is associated with convective storms, not a narrow dew point spread.
Temperature/Dew Point Spread
The difference between air temperature and dew point; a small, narrowing spread signals a high likelihood of fog.
- Spread of 4°F (2-3°C) or less suggests fog is likely
- Fog often forms overnight as temperature drops toward dew point
- Radiation fog is common on clear, calm nights with high humidity
Memory trick: 'Close numbers, cloudy mornings' — small spread means fog.