Why Sunday's storm featured such fat snowflakes in the Mid-Atlantic and the Northeast.

[elleng]

The unusually large snowflakes were as much as two inches in diameter.

Residents from Washington, D.C., to southern New England reported unusually fat snowflakes on Sunday, part of a quick-hitting winter storm that dropped up to 14 inches of snow on Rhode Island. Snowflakes as large as two inches in diameter appeared during the height of the storm, the oversized confetti a curious sight up and down the I-95 corridor.

Although the nation’s capital walked away with only a slushy 0.3 inches at Reagan National Airport, the midday hour featured a blitz of giant snowflakes. Temperatures were two or three degrees above freezing with high relative humidity.

Temperatures in New York hovered in the lower 30s, with similar readings in Boston. The greatest snowfall totals, some topping a foot, were found in southern New England.

The showstopper wasn’t the totals though, but rather the snowflakes themselves. Some were compared to icy pancakes or waffles.

What made for the Goliath snowflakes? A combination of cloud microphysics and the overarching meteorological setup.

For starters, temperatures were marginal to support snow. In fact, many places started off above freezing and chilled once snow began falling into dry air, which dynamically cools the atmosphere.

That left temperatures in the lower to mid-30s within a nearly saturated atmosphere characterized by high relative humidity.

Because of borderline temperatures, the edges of individual snowflakes began melting a bit. In the process, snowflakes probably bumped into one another while still wet and comparatively sticky. But because the air was dry, that liquid ultimately evaporated off the snowflake, simultaneously sucking heat out of the remaining flake and causing those newly joined individual snowflakes to refreeze and accrete together.

“Smaller flakes and crystals tend to stick together when your temperature is near freezing,'>>>

https://www.washingtonpost.com/weather/2021/02/08/big-snowflakes-northeast/?

[Hoyt]

1. Ours was Saturday afternoon/night and the snowflakes were larger than a quarter.

[dem4decades]

2. We had fat flakes but it was a light 8 inches, easy to clear.

[tblue37]

3. Picture:

https://www.washingtonpost.com/wp-apps/imrs.php?src=&w=916

[BigmanPigman]

4. It almost looks fake.

Growing up in Phila we were always on the border between snow, sleet and rain. Usually it turned into rain...no snow days for school (a rarity).