Final answer:
For a winter morning forecast at 8:00 am with partly cloudy skies and 50 km/h winds, the wind-chill effect should be accounted for since it will make the temperature feel significantly colder than the measurable air temperature, specifically around -18°C equivalent in still air.
Step-by-step explanation:
When forecasting the temperature for 8:00 am on a winter day with partly cloudy skies and wind speeds of 50 km/h, with the free-air temperature at 0°C, adjustments need to be made for surface heating or cooling just before sunrise. Since it is just before sunrise, the sun's influence on the temperature is minimal. However, the wind speed and partly cloudy skies will play significant roles in the temperature feeling at the surface. In such conditions, the wind-chill factor needs to be considered. With a wind speed of 50 km/h, the effective temperature will feel much cooler than the actual air temperature, due to the combination of convection and conduction that more rapidly transfers thermal energy away from surfaces and bodies. The presence of clouds might offer slight insulation, but it is the wind that will have the biggest impact on the forecasted temperature feeling.
Based on wind-chill calculations, a wind speed of 15.0 m/s (which is roughly equivalent to 50 km/h) at 0°C can make the temperature feel equivalent to about -18°C in still air. Therefore, the forecast should reflect that the temperature will feel significantly colder than the free-air temperature due to the wind-chill effect. Since sunrise has not yet occurred, there would be no significant surface heating to adjust for. The forecast should account for the high winds leading to a substantially cooler feel, owing to the enhanced rate of heat transfer caused by convection.