Severe Weather Threat Taking Shape

As we approach the noon hour, all seems to be relatively quiet. But don’t be lulled into a false sense of security from the quietness as many different parameters are coming together in a recipe that is likely to lead to some significant severe weather later this afternoon and into early Sunday morning.

The NAM 12Z forecast model has completed its latest run. CAPE values are forecast to reach between 2000 and 2500 j/kg this evening around 10 pm. Lifted index values reach between -4 and -6. So the instability is there. Dew points across Central Alabama are already pushing through the lower 60s which happens to be above the MOS forecast values. I think they will probably reach the middle 60s which just adds to the overall instability.

Helicity – the tendency for the atmosphere to support rotation – is also well above numbers associated with tornado events. Values according to the latest NAM run from 12Z suggest values above 300 and upwards of 600 – values above 150 are what we look for.

Satellite imagery shows a very thick cloud cover over the Tennessee Valley where rain has already occurred. This becomes significant in the mesoscale because both add to the contrast along the frontal boundary. Cloud cover south of the Tennessee Valley shows occasional breaks which will allow additional surface heating to add to the instability.

And lest I forget the high altitudes, a 250 MB jet will be working across the Southeast later today to add more fuel to the lift available for the storms.

And you know that something will probably happen BECAUSE I have to work today! Bummer!!!

-Brian-

Category: Severe Weather