From the site;

"WxRisk.Com is the only weather site on the Internet dedicated to Extended Weather Forecasting and Risk Management. Weather Risk Management is a form of contingency planning in addition to Weather Forecasting. This site's focus is on the 36 hour to 12 day period of weather forecasting, often referred to as the "Extended Range" and "Medium Range" forecast period (ER and MR). The ER period covers from 36 hours to Day 5 while the MR period cover from Day 5 to day 12. "