Sculpting a snowflake
How do temperature and humidity affect flake formation?
Needle-like structures form when the temperature is in the column formation range, but the water saturation increases to produce these slender icicles.
As the saturation of water increases, branches protrude from plates to create fern-like dendrite snowflakes, with sub branches forming from the larger ones.
At the early stages of development, these simple hexagonal crystals form at around -2°C.
Hollow columns Stellar plates Composite shapes
If the conditions change while the crystal is still forming, hybrid shapes can develop. For example, capped columns begin in the same way as hollow columns, but if the temperature drops below -15°C, their hollow ends fill and grow to form flat covers, a bit like a bobbin. Plates will branch out to form elongated, star-like snowflakes at between -10°C and around -20°C. At a similar atmospheric water level as plate crystals but with a decrease in temperature (between -5°C and -10°C), plates extend to form hollow columns.