The proliferation of real-time, unstructured data has revolutionized organizational capacity to anticipate customer behavior; however, traditional predictive methodologies remain ill-equipped to capture high-velocity semantic and behavioral dynamics. To address this limitation, this study proposes an AI-driven customer nowcasting framework that leverages Large Language Models (LLMs) to synthesize heterogeneous, multimodal signals specifically, conversational interactions, real-time sentiment trajectories, search intent, and digital engagement. The objective is to predict short-horizon customer "next moves" while determining the salience, temporal validity, and contextual efficacy of LLM-derived embeddings. Methodologically, historical transactional data are integrated with real-time semantic indicators across diverse customer touchpoints. Predictive performance is rigorously evaluated via rolling-origin cross-validation, benchmarking fine-tuned LLM forecasting architectures against conventional machine learning baselines using RMSE, MAE, MAPE, and the Diebold-Mariano test. This paper decomposes predictive efficacy by signal modality and examines boundary conditions such as behavioral volatility, interaction intensity, and forecast horizon to isolate contexts where foundational AI models yield maximal marginal value. Findings demonstrate that nowcasting accuracy gains are systematically moderated by the depth of contextual reasoning and specific market conditions. By introducing a novel AI-forecasting taxonomy and contingency framework, this study bridged the gap between traditional accuracy benchmarking and advanced data science, equipping practitioners to optimize real-time decision-making in hyper-personalization, dynamic pricing, and proactive customer engagement.