Snow from shallow clouds seeded from power plant smoke stacks
An approximately 600 m thick cloud layer with very low ceilings, resulted in very dense freezing fog (visibility less than 1 km) and patchy freezing drizzle over most of Oklahoma on 31 January 2010. A narrow strip of reflectivity about 5-8 km wide and 25 to 35 km long began to continuously produce light to moderate snow around 19 UTC over western Oklahoma City, Oklahoma. The narrow snow band was oriented in the direction of the low-level (lowest 600 m) steering winds out of the south-southeast. The reason for this snow band appears to be related to additional particulate matter from a coal-fired power plant perhaps acting as ice nuclei, and additional warm moisture air rising up and into, and possibly just above the cloud deck. These together produced small ice crystals that seeded the thicker cloud deck below. With plentiful cloud droplets, some large owing to the reports of freezing drizzle, the reflectivity band intensified and produced snow for over 10 hours. In this paper the radar reflectivity from the KTLX radar at 0.48° elevation is shown in this paper. Another elevation scan was available at 0.49°, but it was essentially identical to the 0.48° elevation scan. Above the 0.49° elevation scan the next available was the 1.49° elevation scan, which was free of weather related radar reflectivity because of very dry air in place at approximately those levels as detected by the KTLX radar.