What do the different precipitation terms mean?


Being known for our gray, damp days, we have plenty of words to try and help give better details on what it might do on a particular day.

Drizzle is a term used for a very light, fine rain. The drops tend to be very small and not very dense.

Mist is similar to drizzle, only the number of drops in any given area is greater. This is usually the case on heavy fog days.

Sprinkles would be something akin to drizzle -- just a few drops here and there.

As for showers, "isolated" and "spot" showers mean just a couple of showers spread over a wide area, with shower coverage less than 30 percent of the forecast area.

"Scattered" showers mean more shower coverage -- maybe 30-60 percent coverage of the area. "Frequent" or "widespread" showers mean a large r area of coverage. Since showers are usually small in size by definition, we might use our every popular "showers and sunbreaks" forecast, which would mean that in between showers, the sun might be out.

Hail forms when rain droplets get pushed higher into the atmosphere by strong upward winds. As the droplets go higher, it freezes into an ice stone known as hail. It then becomes heavier, and falls downward, picking up another coating of raindrops on its way down.

If the updrafts are strong enough, it'll blow the hail back up again, where the coating freezes, making the hail larger, then falling back downward. This process repeats until the hail is heavier than the updraft can support, when it'll finally fall to the ground. The stronger the updraft, the larger the hail stone will become.

It's said it takes an updraft of 56 mph for a hailstone to become golf-ball sized. The largest hailstone recorded was 8" wide (weighing 1.9 pounds!) in Vivian, S.D. on July 23, 2010.

Winter Precipitation

Freezing rain is caused when you have a warm mass of air in the middle altitudes between the ground and the cloud deck, followed by a mass of freezing air near the surface.

When the precipitation falls from the cloud, it will generally be snow. As it encounters the warm air, it will melt into the usual rain. But right before it reaches the ground, it enters the below-freezing air and quickly turns to ice. On impact, it usually freezes to whatever it lands on. That can turn streets into skating rinks in no time.

Sleet is snow that begins to melt as it reaches the ground, but doesn't melt completely. This usually happens when it's around 33-35 degrees at the surface.

Flurries are the drizzle equivalent of snow -- very light snow that isn't strong enough to accumulate.

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