The low-level graphics product is a forecast of aviation weather hazards, primarily intended to be used as a guidance product for briefing the VFR pilot. The forecast domain covers the 48 contiguous states, southern Canada and the coastal waters for altitudes below 24,000 ft. Low altitude Significant Weather charts are issued four times daily and are valid at fixed times: 0000, 0600, 1200, and 1800 UTC. Each 4 panel chart is divided on the left and right into 12 and 24 hour forecast intervals (based on the current NAM model available). The upper two panels (SIG WX PROGs) depict freezing levels, turbulence, and low cloud ceilings and/or restrictions to visibility (shown as contoured areas of MVFR and IFR conditions). The lower two panels (SFC PROGs) are provided by the Weather Prediction Center (WPC) and consist of graphical displays of fronts and precipitation areas.
Weather Symbols from the Aviation Digital Data Service (ADDS)
Surface Front Symbols and Codes from the Weather Prediction Center (WPC)
Precipitation Areas and Symbols from the Weather Prediction Center (WPC)