Ports have always been evolving to satisfy the new or changing demands of stakeholders. In this unstable world, ports as dynamic systems are developed under a high degree of uncertainty. Furthermore, black-swan events, for instance, the financial crisis in 2008, the avalanche in Flateyri (Iceland) in 2020, the COVID-19 pandemic in 2020-2021 make successful port planning a challenging task. Indeed, the ever-increasing complexity of a port system and its long technical lifetime make uncertainty considerations inevitable in the planning process. Therefore, this research presents a structured framework to deal with uncertainties, including opportunities and vulnerabilities, in the port planning process. To this end, a structured stakeholder analysis is performed to effectively and timely engage stakeholders in the planning process. Fuzzy logic 3-dimensional decision surface is used to identify the salient stakeholders. Subsequently, the success of the future port is defined in terms of the specific objectives of the stakeholders. To develop this definition, a problem structuring method and fuzzy multi-attribute group decision-making method are synthesized. Then, a port throughput forecast is conducted that accounts for epistemic uncertainty, including model and parameters uncertainties, and thus increases the reliability of forecast results. The method identifies the influencing macroeconomic variables on port throughput by mutual information and then applies the Bayesian statistical method to forecast the port throughput. Effective actions are planned to seize opportunities and manage vulnerabilities that manifest in the projected lifetime. Therefore, the port can adapt or better withstand the vagaries of the future. The nonlinearity of dealing with uncertainty by application of the framework provides a robust and better plan toward its success. The framework supports decision making under uncertainty and facilitates adaptive port planning. The framework is applied to the Ports of Isafjordur Network in Iceland. The results indicate that the uncertainties mainly present opportunities in the short-time horizon, while in the middle-time horizon the port network is confronted with multiple vulnerabilities.