Mysterious Snow Showers North of Nashville Wednesday, December 11, 2013
Sometime on Wednesday morning snow began to fall and accumulate on roads in southern Sumner County. The unique trait about this snowfall event was that there was nothing on radar or satellite observations that would indicate snow. However, several NWS employees on their way to work witnessed the event, and one of them was able to verify the odd occurrence with photos. Reports were also received from a few NWS Nashville Facebook and Twitter followers. A really quick assessment of current conditions led meteorologists at the Nashville office to speculate that the mysterious and brief snow shower could be attributed to the combination of a few subtle features. The first would be plenty of low level moisture which was causing areas of freezing fog. Temperatures were well below freezing at the time. Sites were reporting temperatures around 23 degrees at 7:00 am. The second contributing factor was a very light but still evident southerly wind. Airports around the area were reporting southerly winds only around 3 knots. The key factor was the terrain of this particular part of Sumner County. The southern portion of the county begins to slope up toward the Highland Rim which is an elevated area that almost encompasses Nashville to the north. The forcing of the moist cold air up into elevated areas likely allowed snowflakes to begin to develop, grow, and fall as snow.
The impacts of the locally isolated snow shower were evident on TDOT's Smartmap and traffic cameras. Traffic along Interstate 65 was almost at a stop from around White House south to Goodlettsville. For reference, traffic doesn't usually back up until south of Goodlettsville. Localized events like this are very rare.