Winter Graph
Description: The winter graph provides a top-down approach to precip-type estimation. The Initial Phase: of the precipitation aloft is specified along with the appropriate pressure/ht/temperature, and the temperature profile is used to identify cold and warm layers that can change precipitation phase.
Numerous quantities are averaged in the dendritic growth zone from -12 to -17 C to calculate a parameter, OPRH, that uses omega, precipitable water, and RH to highlight heavy snow potential.
Not much is known about this technique at this time.