What's worse ... sleet or freezing rain?

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The winter storm system moving across the Carolinas today is bringing all three types of precipitation -- snow, sleet and freezing rain.

We won't have to worry much about snow, as a "nose" of warm air several thousand feet up in the atmosphere is melting the precipitation as it falls. Some of that is refreezing into sleet, and some is reaching the ground as rain -- then freezing.

Anyways, since we're seeing a little of everything this morning, here's a quick primer on how it forms.  And I'm including my two cents' worth on what's worse ...

SNOW

This requires cold air in all levels of the atmosphere.  The only areas seeing snow today are in the northwest mountains, because the "warm nose" (I'll explain this later) isn't expected to reach as far north as the Boone area.

Power outage impact: Usually none, unless the snow is very heavy.

Road impact: Considerable, although crews usually can manage snow with plows and salt.

SLEET

For sleet to fall, we need a relatively thin column of warm air in the middle levels of the atmosphere. Precipitation starts falling as snow, melts on its way down and forms rain droplets, then freezes back into ice pellets as it moves within a few thousand feet of the surface.

Power outage impact: None.

Road impact: Intense.  Sleet causes big problems on the roads, as it tends to melt when reaching the surface and then freezes immediately.  Also, sleet tends to fall when precipitation is heavier. The overwhelming volume of sleet causes pockets of frozen pebbles to form on roads.

FREEZING RAIN

For freezing rain to fall, we need cold air at the upper levels, and then relatively warmer air all the way to the ground. But the surface levels have to be at or below freezing.

Power outage impact: If ice accumulates 1/4 of an inch, tree limbs can fall onto power lines, and we have trouble. When ice accumulates to 1/2 inch or more, there can be widespread problems.  Accumulations in the Charlotte area from today's system are only predicted to be 1/10 of an inch.

Road impact: Often, the main travel lanes on major roads remain in pretty good shape during freezing rain. Ice tends to form on the curbs -- and, of course, on bridges and overpasses, where the road surface is colder. Sidewalks are especially dangerous.  One other thing -- downhill sections of roads tend to get ice, too.  I'm sure there some explanation for this, but you'd have to ask a Physics teacher.