Chance for severe storms increasing across the DFW area ahead of a dryline that is moving into the western portions of the CWA at this time. LAP CAPE and LI is honing in on an area of more favorable instability across the north central counties which is for the most part lining up well with RAP SPC mesoanalysis of ML CAPE and this is confimed by an 18z sounding from Ft. Worth. With fat CAPE in the hail growth zone and very strong mid level lapse rates...large hail should be the biggest threat of the day. With shear values into the 40 kt and above range...convective mode should be supercells. Although large hail will be the primary threat...we are not out of the woods as far as tornadoes are concerned either. The threat for tornadoes will increase in the northeastern portion of the cwa and points north as effective helicity and 0-1 km helicity values are in the 200-300 m2s2 range. LCL values are a little bit higher that ideal for tornadoes so it is possible we see a lot of rotating mesocyclones with few making down to the surface.
As far as low level convergence is concerned along the dryline...Satellite derived winds are not showing as much low level convergence as the RAP mesoscale analysis...shown below.
This makes me think that convective initiation may take a little longer to get going and thus pushing the threat slightly eastward. Fully expect the northeastern quadrant of the cwa to see severe wx but not as confident across the north central near the current position of the dryline. As far as straight line winds are concerned...DCAPE values along the dryline are about 1200 J/kg and observed sounding shows good amount of dry air below 700 mb indicating some downbursts are possible.
Convective initiation values nailed the first radar echos in southern Oklahoma and noted that compared to a fleeting higher CI value, a cluster of high CI and Severe CI values seemed to lend more confidence to the product.
-Jason Bourne
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