Why do weather people say it's going to snow, when there's a 30% chance?

[Critters2]

The Weather Channel "Local on the 8s" starts out saying we'll have snow or rain showers this evening. So, I'm thinking it's going to rain or snow, and figure I should get the beagle walked fast, before it starts. Then it says, "Chance of precipitation, 30%". Is it really possible that these science geeks don't know that a 30% chance of precip means a 70% chance of NO PRECIPITATION?!!

Thank you. This was my pet peeve du jour. Feel free to chime in, or post one of your own.

[PeaceNikki]

1. They're covering their asses. You'd be much more aggravated if they said

"it probably won't snow" and then it does. Instead, you're pleasantly surprised if they say it will and it doesn't.

They know better. They get their asses kicked all the time. Give the weather people a break.

[LeftyFingerPop]

2. Here's why.

Hi Critters :hi:

This is a fair question, and I used to wonder the same thing.

What they are referring to is the probability of precipitation at YOUR specific location within the forecasting area. When a weather system impacts a particular locality, it is not usually seen on weather radar as a solid band of precipitation. You will see breaks of "clear" areas within the weather system. Sometimes these clear areas are quite large, so an area , say, 15 miles away from your home may be getting deluged with rain, while it is perfectly dry at your house.

Depending on the voracity or the enormity of the system, the weather forecasters will assign a probability of precipitation. For a large, intense weather system, they will assign a probability of 100%, meaning that the system will be so large and dense that they can predict with certainty that it will impact your house. A system that will only cause relatively widespread showers in your forecasting area may be assigned a probability of 30% of hitting your home.

[Critters2]

3. Hmmm...that seems fair, I guess.

Thanks, philboy.

Critters
who still suspects their covering their ass :)