This forecast is from a National Weather Service computer model, one of several run daily. This one is called "Eta." Computer models forecast, temperature, winds, moisture and precipitation fields for a given region. This one covers North America and is used by meteorologists at the National Weather Service. The precipitation data shown here is an average for small squares 80 kilometers (49.6 miles) on a side. If the forecast indicates 1 inch of rain for a given area it is possible that 25% of that area gets 4 inches of rain and the rest gets nothing. This will give an average rainfall for this area of 1 inch. It does NOT mean every spot within that area will get 1 inch of rain.