http://ozreport.com/weather.php

XC Skies.

XC Potential

This parameter attempts to identify the locations where cross country is possible based upon a comparison of four different criteria. They are the following:

1. Red. Buoyancy/Shear is greater than 6, average wind speed within the boundary layer (ground through thermal tops) is 10 MPH or less, thermal velocities are greater than 490 feet per minute (2.5 M/S), and the top of the usable lift is greater than 2,000 ft. Above the ground.

2. Orange. Buoyancy/Shear is greater than 4, average wind speed within the boundary layer (ground through thermal tops) is 14 MPH or less, thermal velocities are greater than 490 feet per minute (2.5 M/S), and the top of the usable lift is greater than 2,000 ft. Above the ground.

3. Blue. Buoyancy/Shear is greater than 4, average wind speed within the boundary layer (ground through thermal tops) is 18 MPH or less, thermal velocities are greater than 490 feet per minute (2.5 M/S), and the top of the usable lift is greater than 2,000 ft. Above the ground.

The attempt to characterize good cross country areas is of course subject to interpretation. One pilot's concept of good cross country conditions is not necessarily the criteria for another's. Nevertheless, this parameter gives a quick review of regions where wind speed is low enough to not break apart thermals, and where that wind is not too strong. For those who are after huge cross country distance, this parameter will likely not identify those regions due to a search criteria of relatively light winds aloft areas.