Convective Addiction

3/8/10 Forecast Followup – Isolated severe threat in the Southern Plains

Posted on 05. Mar, 2010 by Skip in Forecasts

The GFS and now the NAM have been trending negatively since I last posted. I was hoping to get more of a classic cold core setup out of this system, but that doesn’t look like its going to happen now. With the system continuously slowing down, the cold air aloft doesn’t overtake the surface moisture wrapping around the low until after dark now. With that we lose our daytime heating to get the low level lapse rates we need to make this cold core setup work. As others have mentioned cloud cover and precipitation in the area is going to further inhibit destabilization it looks like. In order to make something out of this you’d have to look at a more convenctional warm sector target. Instability is going to be low thanks to the lack of heating and marginal dewpoints. Although the 1000 J/Kg plotted at 0z might be enough for some storms to get up, the window of time that instability hangs around is only about 3 hours or so. It looks like the cold air aloft comes in in time to destabilize the area, but we quickly lose it after dark. Storm motions are also going to be cold core like, with a mostly north component. This isn’t bad if any storms can put out a show right after initiation, but they will quickly cross into cooler and more stable air afterwards. I think there is still a chance for some isolated severe weather in western OK and into TX, but at this point I’ve ruled out any chance of making a marathon haul out to the plains.

- Skip