Another Round Of Snowfall Possible For WNC Tuesday Morning
An interesting Shortwave Front will enter WNC early Tuesday Morning, and could cause problems for some around the area. Models are struggling somewhat with temperature profiles as the main moisture enters the area, but short range models are beginning to indicate that a near frozen column will set up over a good portion of WNC. Below you can see the depiction of the most recent 3km Nam and the front that it shows moving in early Tuesday Morning.
Temperature Profiles Questionable
As this storm approaches, a weak high pressure will funnel in a bit of surface cold. Aloft, temperatures will be very cold as an upper level low runs up the Appalachians. Below I have pulled the air temperature sounding from the most recent Nam 3km to dive deep into the profiles of the atmosphere. These charts show meteorologist what the various temperatures are throughout the atmosphere at a given time in the future. The below two sounds are both from Tuesday Morning. The first is from 8am, and the second is from 11am. I have circled the key area on both for you to look at. The blue slanted dotted line represents 0 degrees Celsius or 32 degrees Fahrenheit. As the air parcel approaches the surface in the first, it melts.. but as time progresses and the atmospheres become more saturated.. the precipitation actually wet bulbs and is able to fall to the surface after some time as snow compared to rain. I’ll explain what wetbulbing is in the next section.
What Is Wetbulbing?
Wetbulbing occurs when precipitation falls through air that is not completely saturated. So a portion of the hydrometer(snowflake) evaporates into the less than saturated air as it falls. This evaporation creates a natural cooling effect on the atmosphere that surrounds the falling hydrometer. The air will continue to cool until the air is completely 100% saturated. This is what is being shown above. When precipitation begins to fall, there is an area around 3500’ that will be above freezing. Since the air won’t be completely saturated though (meaning dry air is still somewhat present) evaporation will occur as the snowflake falls through the air, keeping the snowflake from completely melting. Hopefully that makes since. Dry air keeps the snowflake from melting be evaporation, this is a naturally cooling process.
What Do Accumulation Maps Show?
The Nam 3km shows a dusting for many as this approaches from the Southwest, but there are still many details that need to be hammered out with this one. Below you can see what the most recent nam 3km shows regarding snowfall.
Borderline Temperatures Will Make This A Tough Forecast
The temperatures in the lower atmosphere will make this a very difficult forecast where one location may see snowfall, but another location 5 miles up the road only sees rain. To give you an idea of how complicated this setup is, I have attached below the atmosphere temperatures at around 5000’ for you to look at, and then the surface temperatures.
More Details Needed
I will need more short range model data to make an accumulation forecast, but look for that sometime tomorrow as more information comes in. As of now, I believe that snow showers will be possible for many on Tuesday Morning, but I am not sure how it will affect roadways. Check back later for more information.