Yesterday, the temperature reached 80°F (27°C).  And then the cold came.  As of right now, we have a mixture of sleet and snow falling heavily outside, and forecasts claim the situation will get much worse before it ends this evening.  The proclamations are that we will get a good layer of ice before topping it off with an inch or two (2-5 cm) of snow.

Oh, one important point: It’s sticking.

I say that because far too many people misunderstand the physics involved and believe the ground has been too warm to support accumulation.  In fact, I saw a comment on a news site yesterday that said it would take longer than 24 hours below freezing in order for ice to accumulate on the ground (bridges and overpasses notwithstanding).  I laughed when I read that.  Nothing could be further from the truth, and that comment singlehandedly defines the scientific ignorance of too many who believe themselves wise in such matters.

Temperature is only one small piece of the puzzle in determining how quickly the ground cools off.  Precipitation, humidity (above and below ground), and wind also play important roles.  In the case of this cold snap, we have the right mixture of all four ingredients to support rapid cooling.  Anyone looking outside right now would see it has taken less than 24 hours since yesterday’s high for the ground to become capable of freezing and accumulating ice.  It’s called atmospheric physics and thermodynamics.

For that commenter, all I can say is thus: Duh!  Speak with conviction only what you know, not what you think you know, and don’t bellow your ignorance in public forums because that accomplishes nothing except providing fodder to people like me who wish to mock and scorn you.

So, for people in North Texas and all the other places where this storm is or will hit, be careful.  For folks specifically in North Texas, be aware there’s a lot of sleet coming down right now, there’s a bit of snow and freezing rain mixed in with it, and the roads are quickly going from passable to dangerous.  They will become more treacherous as the day moves on and the frozen precipitation continues.