Asynchronous patient portal messaging has become a central mode of ambulatory communication. Its volume is highly variable and increasingly burdensome for clinicians, nurses, medical assistants, and operational leaders. Clinics often respond to inbox surges only after workload has already accumulated. This reactive pattern can prolong response times, intensify staff stress, and reduce the reliability of patient communication workflows. The objective of this predictive model article is to describe a conceptual model for forecasting daily digital patient portal message volume. The model would use disease seasonality, appointment density, medication changes, prior communication behavior, and clinic workload trends as dynamic predictors. The proposed model would combine time-series forecasting with structured clinical and operational features. Gradient-boosted trees, temporal neural networks, or related forecasting architectures could be trained on historical message counts and time-varying predictor variables. Conceptually, the model would provide rolling forecasts of expected message volume for each clinic, day, or operational shift. Forecast intervals could support staffing decisions, workload balancing, and proactive patient communication before inbox pressure peaks. A predictive model for portal message volume could help ambulatory clinics manage digital communication more proactively. Such a system would be expected to improve operational preparedness, staff well-being, and patient responsiveness.