What hazard is expected for a morning departure from KPDX based on its METAR?

The correct answer points to the possibility of frost in the context of a morning departure from KPDX, particularly if the METAR indicates temperatures around or below freezing during the early hours. Frost can form overnight when temperatures drop, especially in clear and calm conditions that are typical during the night, leading to a reduction in aircraft performance and potentially creating hazardous conditions on runways and taxiways.

Morning departures can be particularly susceptible to this hazard, as frost can coat the wings and fuselage of the aircraft, impacting aerodynamics and increasing the risk during takeoff. It's essential for dispatchers and pilots to consider these conditions and perform thorough pre-flight inspections to ensure the aircraft is free of frost or ice before departure.

In contrast, while wind shear, sea breeze conditions, and fog are pertinent hazards in different contexts or locations, they are less likely to be the primary concern for a morning departure at KPDX in typical early spring or fall weather, where nighttime cooling can lead directly to frost formation. Understanding these specific weather phenomena allows for better operational planning and safety management, essential aspects of aircraft dispatching.