Power grids face significant threats from severe disturbances, often triggered by extreme weather, leading to widespread cascading power outages. Although intentional controlled islanding (ICI) is an effective last-resort operational mitigation strategy employed by system operators worldwide to prevent complete cascading blackouts, the impact of large-scale disturbances, particularly weather-induced cascading outages, on when and where to implement the ICI, is neither adequately considered nor reflected in current operational decision-making standards and procedures. This paper proposes a holistic cascading-driven ICI framework that seamlessly integrates advanced weather-related event modelling and cascading risk quantification of high-impact low-probability (HILP) (or tail-risk) events by using a novel ICI based on decision-making mechanism for enhancing the power grid operational resilience. The proposed framework provides a portfolio of mitigation actions proportional to cascading impacts, differentiating between tail-risk events and expected (average) events typically addressed in reliability-oriented studies and current industry practices, while being tailored to both near-real-time operations and short-term operational planning. The proposed framework involves system splitting around black-start units while forming stable and self-sufficient islands, thereby enhancing reliability and resilience. Studies on the IEEE 39-bus and IEEE 118-bus systems demonstrate the effectiveness with a significant improvement in served demand across all simulated initiating events, including up to N - 6 contingencies.