Severe Weather Discussion - 4:15 PM 4/18/13

Here's the updated tornado probabilities from SPC on their latest day 1 outlook. While the tornado probabilities remain the same from earlier, they are not as expansive as earlier. Also, SPC dropped the moderate risk and now just their standard "slight" risk remains, and can be delineated by the brown circle shown above.

Here's the Jackson, MS, radar as of 4 PM this afternoon. Notice a line of storms basically paralleling the MS River, and their associated severe thunderstorm/tornado warnings as seen by the yellow and red polygons, respectively.

The atmosphere has had a little trouble destabilizing, as seen in a sounding earlier this afternoon launched by MSU in Greenville, MS. Still, continued southerly flow is maintaining sufficient moisture (dew point temperatures at least >63 F) across central MS, with Td's closer to 70 right near the front. This is likely due to moisture pooling.

But, it appears the primary risk of severe weather is now shifting/focusing across central MS, basically between highway 82 and I-20. These storms appear to be moving into a slightly more unstable environment as shown by SPC mesoanalysis page. Mid-level lapse rates are a little steeper, towards 7 C/km, as well as CAPE values over 1000 J/kg. So it is possible to see a continued up-tick in severe weather activity at least over the next several hours west of I-55 in MS, or at least a current maintenance of intensity.

The severe risk east of I-55 appears a little more uncertain, but if storms can maintain current intensity, wind damage and an isolated tornado threat will be possible across east MS into west Alabama. A tornado watch remains in place until 11 PM this evening for central and western Mississippi.

Continue to remain weather aware...
IW