SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Tue May 04 2021 Valid 041300Z - 051200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE DEEP SOUTH... ...SUMMARY... Widespread strong to severe thunderstorm development is expected today across the Deep South. The primary risk will be scattered severe gusts resulting in wind damage and an accompanying risk for a few tornadoes. ...East Texas/Deep South/Tennessee Valley... A moist/potentially unstable air mass exists across a broad region today, especially from east/southeast Texas to much of Louisiana/Mississippi/Alabama. As noted in 12Z regional observed soundings, this is where an elevated mixed layer/plume of steep mid-level lapse rates of 7.0 C/km (or greater) is established atop rich boundary layer moisture (surface dewpoints lower 70s) that precedes an eastward-moving cold front located near the ArkLaTex and east/southeast Texas early today. An ongoing MCS across middle/eastern Tennessee will continue to pose a severe risk early today, mainly in the form of damaging winds and brief tornado potential, as it continues generally eastward toward the southern Appalachians. Elsewhere, near/just north of a front, other strong to severe thunderstorms are expected to develop this morning across south-central/east Texas with hail as the primary severe threat initially. For additional short-term information, see Mesoscale Discussion 521. Influenced by the progressive southern stream shortwave trough, storms should expand in coverage/intensity into midday/early afternoon toward the ArkLaMiss vicinity with a corresponding uptick in wind damage potential expected aside from a persistent severe hail risk. Strengthening belt of southwesterly low/mid-tropospheric winds will support organized storms including upscale quasi-linear growth this afternoon. The net result is a swath of damaging wind gusts are expected this afternoon especially from central/eastern Louisiana into central/southern Mississippi and Alabama, and eventually western Georgia by early evening. While damaging winds are likely to be the most common hazard, some hail and a couple of tornadoes will also be possible. ...Ohio Valley and Mid-Atlantic States... Scenario will be influenced by an early day MCS across the Tennessee Valley/southern Appalachians and extensive showers/thunderstorms across the lower/middle Ohio River Valley and related cloud canopy. For these reasons, considerable uncertainty exists regarding the degree of diurnal destabilization across the Ohio Valley later this afternoon, although a few strong/severe thunderstorms may develop near/ahead of an east/southeastward-moving cold front. The remnants of the MCS centered across eastern Tennessee early today may persist eastward across the Appalachians with renewed development this afternoon into downstream areas of the Mid-Atlantic/Carolinas, with isolated wind damage as the primary hazard. ..Guyer/Kerr.. 05/04/2021
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