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SPC Mesoscale Discussion: Severe Potential… Watch Possible 345…

| August 20, 2018 @ 5:58 pm

SUMMARY…Isolated 50-60 mph gusts, capable of wind damage, are possible with any supercell or stronger multicell early this evening. Although a severe thunderstorm watch will probably not be needed across north-central MS to the south of the existing watches, this area will be monitored.

DISCUSSION…Radar shows a broken cluster of a mixed mode of supercells and multicells across the lower MS Valley early this evening. This activity has developed on the southern periphery of stronger forcing for ascent that is largely displaced to the north of the middle MS Valley. An extremely moist axis extends north-northeastward over the Delta region with upper 70s dewpoints yielding lowest 100mb mean mixing ratios of 19 g/kg. Despite the relatively weak lapse rates per forecast soundings, around 3000 J/kg of MLCAPE exists from northeast LA into northern MS. An outflow boundary from earlier-day convection over southeast MS and west-central AL is slowly progressing northwestward across the greater Jackson-Columbus corridor. The focus for severe thunderstorm potential will be north and west of this boundary during the evening as storms gradually move east. Wet microbursts appear to be the primary threat with the stronger storms. Tornado potential will likely be relatively limited across northern MS given a veer-back-veer signature evident on the area VADs.

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