Insider Blog: Why it takes longer for snow to stick on some surfaces

As the snow fell Thursday, accumulations were first noticeable on elevated and grassy surfaces.

This is largely thanks to the heat that the ground holds. Even though our air temperatures have been below freezing for much of the day, ground temperatures and specifically pavement temperatures, may still be warmer.

Pavement absorbs energy from the sun and ambient air temperature, and does a really good job holding it. It is also insulated by the ground, meaning that cold air slow to impact its overall temperature. Grassy and elevated surfaces have much less mass than a layer of pavement and are much more exposed to the cold air, which allows them to cool more quickly.

Along these same lines, bridges are often another area where we typically see snow accumulation first. Their elevated nature leaves them more exposed to cold air. This means what falls will stick relatively quickly if the air temperatures is below freezing.