Severe thunderstorms are expected today across the Lower Great Lakes, Mid-Atlantic, and Southeast. More isolated severe thunderstorms are possible this afternoon and evening across much of central and east Texas, southwest Oklahoma, and the mid/upper Mississippi Valley.

Locations:

  • Primary Risk Areas: Much of the Atlantic Seaboard and north/central Texas.

Threats:

  • Damaging Winds: Expected across the Lower Great Lakes, Mid-Atlantic, and Southeast.
  • Large Hail: Particularly over north-central and parts of central Texas.
  • Isolated Tornadoes: Possible mainly across the Mid-Atlantic and Southeast.

Timing:

  • Storm Initiation occurs midday to afternoon and continues into the evening. In Texas, it occurs late afternoon into the overnight hours.
  • Peak Threat: This afternoon and evening.

Discussion:

Atlantic Seaboard to Southeast:

  • Setup: A complex synoptic-scale trough with several shortwaves and vorticity maxima will proceed eastward across the Upper Great Lakes and the Ohio/Tennessee Valleys. A northern-stream perturbation will pivot over Lake Huron and the Upper Ohio Valley/Lower Great Lakes today. In contrast, a strong upstream perturbation moves southeastward to southern MN and IA by 00Z.
  • Surface Analysis: A well-occluded low over northern Lake Michigan with an occluded/cold front arching across lower MI, OH, the Ozarks, and north-central to west-central TX will precede extensive convective outflow across the Appalachians, Southeast, and Mid-South.
  • Storm Development: Ongoing complexes of strong-severe thunderstorms over AL and GA may produce continued damaging wind, isolated large hail, and a tornado while moving into a favorably moist and destabilizing airmass over GA. Additional thunderstorms are expected to develop along the front from the Mid-Atlantic into upstate NY by midday and through the afternoon.
  • Severe Potential: Surface dewpoints in the low/mid-70s across GA and the Carolinas Piedmont/Coastal Plain to the 60s over the rest of the outlook corridor, combined with veering winds with height and related hodograph curvature, will support effective SRH of 150-300 J/kg, with potential for supercells and some tornado threat, as well as organized multicells in lines or clusters.

Southern Plains:

  • Setup: Isolated to scattered thunderstorms are possible from north-west TX southeastward across parts of LA and southern MS. Damaging gusts and large hail are the most significant concerns, with a conditional potential for isolated supercells offering large to very large/destructive hail, especially over north-central and parts of central TX.
  • Surface Analysis: A dryline will remain in place across north-central TX to northern Coahuila, becoming more sharply defined as moisture returns northward.
  • Storm Development: Strong diurnal heating and decreasing EML-related capping with eastward extent will result in more significant convective potential along/ahead of the front this afternoon from northwest TX to the central Gulf Coast states.
  • Severe Potential: Surface dewpoints in the 70s F and steep midlevel lapse rates will support MLCAPE of 4000-5000 J/kg over central/north TX, decreasing to 2500-3500 J/kg over southern MS. Veering winds with height and a lengthy hodograph structure will be well-suited for hail production in any sustained supercells. Coverage concerns linger due to forecast height rises across the region behind the synoptic trough.

Technical Chase Discussion

Hrrr 2024052712 011 32.89--97.67.

A pulled sounding from Northern Texas shows an environment strongly unstable with sufficient 0-6km bulk shear values for storms to produce large and damaging hail if one can get going. Capping is minimal, but large-scale subsidence aloft due to rising heights will make forcing for ascent negligible. A storm that can form in this environment would likely be somewhat isolated and quite powerful. Supercell risk-wise, the 0-3km SRH and BRN both point to only transient structures, but a supercell is likely due to the likelihood of a robust right turn that would locally increase both values to supercell levels. Tornado risk isn’t zero, but it is very low given extremely weak low-level wind shear.

Ref1km 004hmax pb40.sp.f02400.As of this writing, the HREF from last night only had a 10-30% chance of storms in the North Texas region, which seems about right. Today is a true boom or bust. If a storm goes, wow. If a storm doesn’t, what a beautiful sunset indeed.