Icing Areas – Areas expected to experience trace to light icing are green, areas expected to experience light to moderate icing are yellow, and areas expected to experience moderate to severe icing are red.
Icing Reports — Pilot Reports containing icing are depicted in yellow. Included from top to bottom are: Flight Level in hundreds of feet, aircraft type / time of report in UTC, outside air temperature in degrees Celsius, and the intensity and type of icing reported. An icing symbol also represents the intensity of icing. The diamond shape indicates the position of the aircraft when the report was issued.
Freezing Levels — White dashed lines indicated the freezing level contours as determined from the most recent Radiosonde and numerical model data. Contour intervals are labeled in hundreds of feet and drawn at 2000 foot intervals.
AIRMETS — Icing AIRMETS are graphically depicted as solid light blue lines. The intensity of the expected icing is depicted using icing symbols. The altitude range of the icing is labeled to the right of the icing symbol, with the upper altitude to the upper right, and the lower altitude to the lower right. Altitudes are labeled in hundreds of feet. FRZLVL is used to indicate that the actual freezing level is the lower altitude limit of icing. The start and expiration time of the AIRMET is depicted below the icing symbol, with the two digit day of month followed by the 4 digit hour and minute in UTC. Icing AIRMETS (named ZULU) are issued for areas expected to experience moderate icing conditions (outside convective activity).
Maps are updated every hour and are available between 30 and 45 minutes past each hour.
Icing Areas — – Areas expected to experience trace to light icing are green, areas expected to experience light to moderate icing are yellow, and areas expected to experience moderate to severe icing are red.
Freezing Levels — White dashed lines represent freezing level contours, drawn at 4000 foot intervals. Lines are labeled in hundreds of feet. A white dotted line represents the surface freezing contour when present.
For the U.S. and Regional U.S., maps are updated hourly for the 03, 06 and 09 hour forecasts. Maps are updated every 6 hours for the 12, 18 and 24 hour forecasts. For international areas, maps are updated every 6 hours for the 12, 18 and 24 hour forecasts.