Day 34: Snow Melt – Aloft!
A very active weather pattern is shaping up for the next 10 days or so beginning with a shortwave tough (upper-low) moving through the southern United States. I debated whether to talk about this upper-low as it currently is moving through the south central US or discuss what will happen (partly as a result of this upper-low) along the east coast starting tomorrow into the weekend (another major snow storm for the mid-Atlantic states!). I figured there would be a lot to talk about tomorrow with respect to the mid-Atlantic snow so I decided to talk about the southern plains tonight.
Below is a radar image taken tonight from the National Weather Service radar in southwest Oklahoma. At the time this image was taken, southwest Oklahoma was experiencing light to occasionally moderate intensity rain – at the surface. Why do I make this distinction? Because above 6000 feet above the ground it was actually snowing!
The radar image above has what is known to meteorologists as a “bright band” signature. The bright band is the dark green and yellow pixels that appear to make a circle around the radar (the cyan dot with KFDR label). What is happening is that high in the cloud, the precipitation starts out as snowflakes in the cold air aloft. As the snow falls and gets closer to the surface it encounters air that is above 0C (32F) that causes the snowflake to begin to melt. This partially melted snowflake shows up on a radar image much more easily than a snowflake or a raindrop itself would show up. This causes the level with the most partially melted snowflakes to show up as a bright band or bright circle around the radar site. (Without getting in the math and physics of it all, everywhere along the the dark green and yellow circle is essentially at the same height. It has to due with the curvature of the earth’s surface.)
Because the image below has a fairly easily identifiable bright band, I can say with a lot of confidence that it is snowing higher up in the clouds. Now, the million dollar question, will any of those snowflakes make it to the ground?
About Patrick
Patrick Marsh is a Ph.D. student at the University of Oklahoma's School of Meteorology. He earned a Bachelors of Science in Mathematics and Physics (cum laude) from the University of Arkansas in 2005 and a Masters of Science in Meteorology in 2007. In addition to working on his doctorate, Patrick serves as the National Severe Storms Laboratory Liaison to the Hazardous Weather Testbed where his research interests lie in working with operational forecasters, data mining, data visualization, and all things high-impact weather. For more about Patrick's work, check out his complete CV!
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