Administrators NorthGeorgiaWX Posted December 9, 2023 Administrators Share Posted December 9, 2023 SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1157 PM CST Fri Dec 08 2023 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE LOWER TO MID MISSISSIPPI VALLEY NORTHEASTWARD INTO THE TENNESSEE VALLEY... ...SUMMARY... Severe thunderstorms, capable of producing a few tornadoes, scattered damaging winds, and large hail, will be possible from the lower Mississippi Valley northeastward into the Tennessee Valley this afternoon and evening. Marginally severe storms could also develop in parts of the Ohio Valley and in the central Gulf Coast region. ...Lower Mississippi Valley/Tennessee Valley/Ohio Valley... A positively-tilted mid-level trough and an associated belt of strong flow will move eastward into the mid Mississippi Valley today. At the surface, a cold front will advance southeastward into the mid Mississippi Valley as a moist air mass advects northward across the central Gulf Coast states and Tennessee Valley. Surface dewpoints are forecast to increase into the 60s F across northern Mississippi, northern Alabama and in the western half of Tennessee. During the day, elevated thunderstorms appear likely to develop on the northern edge of the moist air mass, with a cluster of storms moving east-northeastward across northern Arkansas and western Tennessee. This cluster may be associated with a marginal threat for hail and wind damage. To the south of this cluster, the airmass should become moderately unstable by early afternoon, with MLCAPE peaking in the 1500 to 1800 J/kg range, according to RAP forecast soundings. During the mid to late afternoon, thunderstorms are expected to initiate along and ahead of the front, with a gradual increase in storm coverage taking place across the region. The eastern edge of the mid-level jet will overspread the warm sector this afternoon, creating strong deep-layer shear favorable for severe storms. 0-6 km shear values are forecast to increase into the 50 to 60 knot range, suggesting supercells will be possible. Storm-relative helicity in the 200 to 300 m2/s2 range will support a tornado threat, especially with cells that remain discrete. Although a tornado threat is expected to develop over a broad area from far eastern Arkansas northeastward into middle Tennessee, the most focused tornado potential may be from northwest Alabama into southern Tennessee. In this area, the combination of low-level shear and instability is expected to become maximized during the late afternoon and early evening. In addition to supercells, multicell clusters and line segments will be likely. The stronger rotating storms and multicell line segments may be capable of damaging wind gusts. The large hail threat will likely be associated with the more widely scattered supercells that develop further west into parts of the lower Mississippi Valley, where mid-level lapse rates are forecast to be steeper. The severe threat over the Tennessee Valley should persist into the mid to late evening as a line segment gradually develops ahead of the cold front. Further north into the Ohio Valley, instability is forecast remain weak in the afternoon and evening with RAP forecast soundings having MLCAPE peak in the 500 to 800 J/kg range. In spite of this, 0-6 km shear from 60 to 70 knots will support an isolated severe threat. Any potential for tornadoes, wind damage and hail is expected to remain isolated and marginal. ..Broyles/Wendt.. 12/09/2023 Read more View the full article Quote Link to comment Share on other sites More sharing options...
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