1. A computer-based system for generating a weather-modified managerial plan that represents the future impact of weather and other factors on retail sales, comprising: first means for providing store information; second means for providing weather data, said weather data including, historical weather data, normal weather data, and forecasted weather data; third means for providing information external to retailer store environment; database initializer means for performing one or more transformations of said store information, said weather data, and said external information to produce databases; correlation processor means for generating a weather impact model, said weather impact model expressing a correlation between said store information and said external information contained within said databases with said historical weather data, and for substituting said normal weather data for said historical weather data in said weather impact model to generate deweatherized data; and forecasting processor means for substituting said forecasted weather data for said normal weather data in said weather impact model to produce a weather-modified managerial plan.