METAR weather code reference for SN (Snow)
Frozen precipitation in the form of ice crystals, most often occurring as snowflakes. Snow significantly reduces visibility and is a primary concern for aircraft icing, runway contamination, and braking action. Often reported with intensity modifiers.
Here are common ways SN appears in real METAR observations:
-SN+SNSN BRThese METAR codes are commonly seen alongside SN or describe related weather phenomena:
Very small, white, opaque grains of ice that are essentially the frozen equivalent of drizzle. Snow grains are flat or elongated, usually less than 1 mm in diameter, and fall in small quantities from stratus clouds. They rarely reduce visibility significantly.
Small, translucent balls of ice that bounce when hitting the ground. Ice pellets (sleet) form when snowflakes melt in a warm layer aloft and then refreeze in a cold layer near the surface. Their presence indicates a complex temperature profile and often means freezing rain may be nearby.
Also known as diamond dust, ice crystals are tiny, unbranched ice particles that fall from a clear or nearly clear sky. They are most common at very cold temperatures (below -30C) and can create optical phenomena like sun dogs and halos. Often observed at high-altitude airports in arctic regions.
Indicates that liquid precipitation is freezing upon contact with surfaces at or below 0 degrees Celsius. Freezing rain (FZRA) and freezing drizzle (FZDZ) are among the most dangerous weather conditions for aircraft, causing rapid ice accumulation on wings, control surfaces, and engine inlets. Freezing fog (FZFG) deposits rime ice on exposed surfaces.
Weather phenomenon raised by the wind to heights of 6 feet or more above the surface, significantly reducing visibility. Commonly used with snow (BLSN), dust (BLDU), and sand (BLSA). Blowing snow is especially hazardous because it can create whiteout conditions and make it impossible to distinguish the horizon or runway edges.