Re:Why not tethered? (Score 3, Informative)

Aircraft under VFR flight rules do fly hither and yon, where ever they want (in class G airspace) and flight plans are not always required or even need to be approved. Thats just how SAR finds you when you have an "unplanned landing". There is no requirement for contact with ATC, and you can fly as low as 500 feet AGL, and even lower if the weather is closing in. Sending up 2-3 balloons a day would not be a big deal but making a mesh network of weather balloons, say 20 a day would cause a hazard. Maybe going as far as switching a large area to restricted airspace. Which would require printing of new maps/NOTAMS.