Skywarn is a great service. Basically, the National Weather Service (NWS) needs "ground truth" reports of weather events. One reason is because their radar systems (which are excellent) are not able to state with certainty what weather you actually experience in your location.
Skywarn specializes in severe weather. This can range from the boring "2 inches of snow the backyard" reports to heart-thumping "tornado chasing" (which you are not required to do, by the way). One can send their report by phone, email, or even ham radio. Good reporting and measurements can improve the forecasting and warning systems and quite literally save lives.
The training the NWS staff provides is free and detailed. They are given by personnel from the local NWS offices. I took the Basic class in 10/2015 and became a certified Skywarn spotter. You typically get assigned an ID you can reference when you send in a weather report.
So far, I have reported snowfall during the recent blizzard on the east coast, as well as ice formation.
If you're interested in weather, science, ham radio, or public service, please check out Skywarn. You can even read their training materials for free. Do so, and you'll be lightyears ahead of the lay public. Become a certified Skywarn spotter, and you can learn about weather, contribute to science, as well as save lives.
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