Sounding at Syracuse during the heaviest snow
Notes:
This slide shows a NAM forecast sounding valid at 12z on the 10th at Syracuse, around the time when the heaviest snow band was moving across the area. The Froude number, which is a function of wind speed and stability, was calculated through a layer from 950 to 900 mb, which is about the elevation on the higher hills south of Syracuse.
The Froude number has been shown to be an indicator of how much blocking occurs of flow in the atmosphere. Large values occur with large wind speeds perpendicular to terrain features, and with weak stability. Small values indicate lighter flow and larger stability. Values less than 1 indicate blocked flow and can indicate that heavy snow is as likely at lower elevations than over higher terrain. Higher values indicate that flow can proceed over higher terrain, with the resulting upward vertical motion forced by topography favoring heavier precipitation near or downstream from higher terrain. In this case, the Froude number of nearly 3.0 would indicate that higher terrain would be favored for heavy precipitation.
Slide 25