METAR weather code reference for GR (Hail)
Ice precipitation consisting of balls or irregular lumps of ice with a diameter of 5 mm (about 1/4 inch) or greater. Hail is associated with strong thunderstorms and poses a severe hazard to aircraft, capable of causing structural damage to airframes, windshields, and engines.
Here are common ways GR appears in real METAR observations:
GR+TSRA GRTS GRThese METAR codes are commonly seen alongside GR or describe related weather phenomena:
Small hail (graupel) or snow pellets less than 5 mm in diameter. These ice pellets form when supercooled water droplets freeze onto snowflakes. Less damaging than full hail but still indicates convective activity and potential for icing conditions.
A convective storm producing lightning and thunder. In METAR reports, TS indicates that thunder has been heard at the station within the observation period. Thunderstorms are among the most dangerous weather phenomena for aviation, bringing turbulence, wind shear, hail, heavy rain, and microbursts.