Appointment cancellations undermine clinic efficiency, disrupt continuity of care, and reduce access for patients waiting for limited appointment slots. Many cancellations may be preventable when risk is recognized early enough for staff to intervene with reminders, rescheduling support, transportation assistance, or telemedicine conversion. Existing appointment-risk models often emphasize historical attendance and demographic information while underusing scheduling notes, patient communication history, weather conditions, and transportation barriers. They also frequently provide risk scores without patient-specific explanations that staff can translate into meaningful outreach. This article proposes an explainable machine learning framework for predicting preventable appointment cancellations before the appointment occurs. The framework is designed to identify not only which appointments may be at risk, but also why the cancellation risk is elevated. The proposed framework uses a gradient-boosted classification model trained on structured scheduling variables, prior attendance behavior, communication history, weather-linked features, transportation indicators, and natural language processing outputs from scheduling notes. SHAP-based explanation layers would decompose each prediction into interpretable drivers that can be reviewed by scheduling staff, clinic managers, and governance teams. Conceptually, the framework would output a cancellation risk score together with a natural-language explanation of the dominant drivers. These outputs could support targeted interventions such as reminder escalation, proactive rescheduling, transportation support, or conversion to a virtual visit when appropriate. An explainable framework for preventable appointment cancellation prediction could shift patient access management from reactive backfilling toward proactive retention. By combining heterogeneous access signals with transparent attribution, clinics could better align outreach resources with patient-specific barriers.