Monday, January 5, 2009

Ice for the Mid-South?

As relayed through this blog late last evening from the NWS, all eyes are on the potential for light freezing rain during the day today. Here's an update. For more rural areas of west TN, as well as the Jackson area, I'll refer you to an excellent post this morning on JacksonWeather.net's blog.


In the metro area, temperatures hover around 33-35 degrees at 5am (see temp map below) with a light northeasterly breeze. The dewpoint (a measure of the moisture in the air at the surface) sits in the mid 20s. MWN StormView Radar shows no precip as of now. The cold air at the surface is very shallow, with temperatures increasing with height above the first couple thousand feet. This temperature profile, and the dewpoint, are keys to today's weather.



I expect precipitation to start to materialize after lunchtime, with increasing intensity as we head towards rush hour and into the evening. With abundant cloud cover, low dewpoints, and a northeast wind, the surface temp will struggle to rise much at all today, and when precip starts, it may actually fall a couple of degrees initially (a process Meteorologists call wetbulbing, as the air saturates the initially drier air near the surface). As rain begins to fall heavier, I believe the surface temp will stop falling and may actually begin a slow climb overnight.


All of this means that initial light rain that falls could freeze on contact, especially on exposed surfaces, bridges, and overpasses, depending on how far the temperatures falls in those first few hours that the precip falls. The most critical timeframe, I think, in the metro area will be from noon until about 4pm, and particularly in the northern suburbs of Arlington, Millington, Lakeland, and points north. By rush hour, I expect that most everyone will be above freezing, though a few slippery spots may still exist on overpasses of 385, I-55 north of Memphis, and possibly I-40 east of Memphis.


The next thing to watch will be the possibility of flooding as the ground is still fairly soaked and we may see as much as 2" of rain by Tuesday evening when it tapers off. In fact, Flood Watches are in effect for areas south of the city. I'll keep an eye on all of it all day, so stay tuned to this blog and the forecast over at MemphisWeather.net, as well as commercial outlets and NOAA All-Hazards Radio, for complete coverage.

1 comment:

jacksonweather said...

Thanks for the plug, my friend. You do an excellent job yourself! Have a good week!