The Citizen Weather Observer Program (CWOP) is a network of privately owned electronic weather stations concentrated in the United States but also located in over 150 countries. Network participation allows volunteers with computerized weather stations to send automated surface weather observations to the National Weather Service (NWS) by way of the Meteorological Assimilation Data Ingest System (MADIS). This data is then used by the Rapid Refresh (RAP) forecast model to produce short term forecasts (3 to 12 hours into the future) of conditions across the United States' lower 48 states. Observations are also re-distributed to the public.