A Center Weather Advisory is issued for hazardous weather when there is no existing Aviation Weather Center or AAWU advisory
in effect. A CWA may also be issued to supplement an advisory that has already been issued by AWC or AAWU.

A CWA should be issued when each of the following conditions exist:
 1. There is no existing AWC or AAWU advisory in effect.
 2. Any of the following condition occur:
   a. Conditions meeting convective SIGMET criteria (see NWSI 10-811)
   b. Icing – moderate or greater
   c. Turbulence – moderate or greater
   d. Heavy and extreme precipitation
   e. Freezing precipitation
   f. Conditions at or approaching Low IFR (See NWSI 10-813)
   g. Surface wind gust at or above 30 knots
   h. Low Level Wind Shear (Surface – 2000 feet)
   i. Volcanic ash, dust storms or sandstorms
   j. When a hazard has grown significantly outside of the boundary defined by the AWC or AAWU advisory
   k. To upgrade a thunderstorm advisory to include severe thunderstorms
   l. To upgrade an AIRMET to include isolated severe turbulence or icing (If greater
      than isolated severe turbulence or icing is occurring, then a new (nonsupplementary) CWA should be issued
   m. To define a line of thunderstorms within a larger area covered by the AWC or AAWU advisory
   n. To better define hazards expected at a major terminal already within an AWC or AAWU advisory
 3. Anything that in the judgment of the CWSU forecaster will add value to an existing advisory
 4. In the forecaster's judgment the conditions listed above, or any others may adversely impact the safe flow of air
    traffic