Since snow is on everybody’s mind today, I need to share with you something remarkable I witnessed early Sunday morning.
Take a look at this short video (above). Can you see the little snowflakes falling? Ordinarily, this wouldn’t be any big deal (especially compared to what’s coming Monday night). However, these snowflakes were falling out of a clear blue sky!
That’s right, there was not a single cloud from horizon to horizon. The air was calm (so they weren’t blowing off the roof or trees), and the temperature was 10 degrees (-12 degrees Celsius).
Take a look at the photos of the little snowflakes I caught on my glove.
These are actual snowflakes -- we call them dendrites. In ultra-cold weather, sometimes little ice crystals called columns develop, but these definitely were dendrites and not columns. Aren’t they pretty?
So how does snow fall out of a clear sky?
Take a look at this “sounding” – a vertical profile of temperature (orange line) and dewpoint (green line) from the surface up to about eight miles aloft.
Notice two things just above the surface:
- The two lines are very, very close together. This means a saturated atmosphere.
- The temperature gets warmer in that initial layer just above the surface. That’s called a temperature inversion, and acts as a “cap” or “lid” between that moist low level air and the drier air above (where the lines get farther and farther apart). So, in essence, that low-level moisture was trapped.
What then happened was that this low-level water vapor condensed onto what we call condensation nuclei (dust), and formed beautiful little snowflakes, which fell without a cloud to fall from! I’ve never seen this before -- what an amazing thing to experience!
Let me know either on Facebook or Twitter if you saw this, too! (@PGLocal4)