Sounding 4 Discussion

Discussion on Sounding 4 - Snow

The wind structure: A good southerly flow exists through all levels except the surface at this time at TOP. From the wind structure and not looking at any plan view maps, this sounding environment could be located downstream (east) of a larger scale trough. This is different from the other soundings as it does not have a strong inversion and is moist through the depth of the lower tropopause.

The temperature/moisture structure: with the above wind profile, the more classic freezing rain / mix of winter weather is not so apparent or not expected. The sounding is completely below freezing, a moist area exists below -12C near the 650 mb level, and no dry layers exist. Thus, ice is produced above 650 mb by supercooled droplets collecting on IN, and the particles continue to grow (and never melt) as they fall. Snow! All of the big three are satisfied for snow:

1. No dry layers in the lowest troposphere.
2. Cloud minimum temperature at < -12 to -15 C.
3. No warm layers exist to produce melting.


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