The purpose of the Communication/Navigation Outage Forecasting System (C/NOFS) is to detect and forecast ionospheric irregularities that adversely impact communication, navigation and surveillance systems. The C/NOFS consists of ground sites that monitor the radio link to geosynchronous and GPS spacecraft, a fully-instrumented monitoring satellite scheduled for launch in 2005 and a central data collection facility that creates scintillation warnings in near real-time. The C/NOFS spacecraft will be launched into a low inclination (13°), elliptical (~ 375 x 710 km) orbit. Sensors on the C/NOFS spacecraft measure the ambient ionosphere near the equator and detect density fluctuations which cause scintillation. Ionospheric irregularities often occur after sunset within ±20° of the magnetic equator. These irregularities can be fairly benign, causing a small amount of radio scintillation and perturbing only UHF/VHF communications, or they can be very severe, causing L-band scintillation that interfere with the functioning of GPS receivers. In these severe cases, the ionospheric irregularities can extend beyond 1000 km altitude. One of the challenges of this project is to go beyond detecting irregularities and to predict scintillation-producing irregularities up to 8 hours into the future and estimating changes in the climatology 24 hours or more into the future.