Final answer:
A precise temperature forecast requires considering factors like solar radiation and local geography, though surface temperatures are typically warmer than free-air temperatures in clear conditions. Without specific details, an exact forecast is speculative.
Step-by-step explanation:
To forecast the final temperature after adjusting for surface heating or cooling on a spring afternoon with a free-air temperature of 4°C, you would need to consider several factors. On a clear day with light winds, it is reasonable to expect some warming due to solar radiation. Nevertheless, without specific knowledge of the local geographic features, time of day, and atmospheric conditions, providing an exact number is speculative. In general, surface temperatures can be several degrees higher than free-air temperatures in similar conditions due to direct sunlight.
A mathematical approach to a similar question might be demonstrated in situations where specific changes are indicated, such as a cold front dropping the temperature by a known amount. Additionally, energy expenditure calculations, such as keeping an indoor environment at a specified temperature compared to the outside, require an understanding of thermodynamics.