Administrators NorthGeorgiaWX Posted January 9 Administrators Posted January 9 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0658 AM CST Tue Jan 09 2024 Valid 091300Z - 101200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE SOUTHEAST...FROM THE EASTERN GULF COAST TO THE COASTAL CAROLINAS... ...SUMMARY... Tornadoes (some strong), damaging to severe gusts and isolated hail are expected over parts of the Southeast, from the eastern Gulf Coast to the coastal Carolinas. ...Synopsis... The main mid/upper-level feature for this forecast will be a well- developed cyclone, initially centered over the KS/OK/MO tri-state region, along a synoptic-scale trough extending from MN to the Arklatex to near BRO. The 500-mb low is expected to move northeastward through the period, reaching to near HUF by 00Z and over southern ON late tonight. Meanwhile, the trailing trough will become more neutrally to slightly positively tilted, crossing AL around 00Z and moving offshore from NC around 12Z tomorrow. At the surface, a low was analyzed at 11Z near STL, with occluded front southeastward into AL, and cold front across southern AL, the western FL Panhandle, and the north-central Gulf. A warm front was drawn from south-central AL southeastward over the northeastern Gulf, then diffusely eastward over central FL and adjoining parts of the Atlantic. The warm front may shift/redevelop quickly northward today into northern FL and parts of GA, as well as reaching the Carolinas during the afternoon. The low should move erratically northeastward to southern Lake Michigan by 00Z, becoming more deeply occluded. In the meantime today, the cold front should sweep across much of the Southeast, extending from central/eastern NC south- southwestward across Atlantic waters to central FL by around 00Z. The cold front should continue to be preceded by a well-organized squall line. ...Southeast... A strong-severe squall line, with embedded bow/LEWP formations and sporadically tornadic meso/misovortices -- was evident over southeastern AL and the western FL Panhandle. Isolated supercells ahead of the line this morning, in the FL Panhandle and eventually into portions of southwestern GA -- will pose a tornado, wind and isolated severe-hail threat as well. Even for relatively short- lived tornadoes, fast translation can lengthen paths more than usual, and enhance potential damage intensity on one side to significant (EF2+) level. For more detailed near-term coverage, see SPC tornado watch 4 and associated mesoscale discussions. The main convective band should continue to produce damaging wind and occasional QLCS tornadoes as it moves eastward over the outlook area today. A relative min in forcing for discrete, warm-sector supercells, as well as in upstream boundary-layer theta-e available to the squall line, remain plausible, and account for a somewhat lower (but still well worth outlook coverage) all-hazard severe threat between the northeast Gulf Coast and Carolinas areas. Then potential is expected to ramp up again this afternoon into early evening as the activity nears the Atlantic Coast, and as warm/moist advection from a modifying Atlantic boundary layer supports increasing potential for oceanic supercells to reach the shore there. Warm-sector MLCAPE should reach the 1000-1500 J/kg range the next few hours in the FL Panhandle, and mid/late afternoon over portions of the coastal Carolinas and west-central/central FL. Otherwise, MLCAPE of 200-700 J/kg should be common over most of the outlook area just ahead of the QLCS. Vertical shear, by almost any common measure, will remain strong area-wide. 50-60-kt effective-shear magnitudes should be common, along with 35-50 kt vectors in the lowest km. Mass response to the progressive mid/upper cyclone and trough will continue to yield a 65-95-kt LLJ shifting east-northeastward across the preceding warm sector. This will contribute to effective SRH over 400 J/kg in the warm-frontal zone, and 200-500 J/kg in the warm sector. In addition to enlarging low-level hodographs, LLJ-associated momentum transfer from the intense winds just above the surface, in strong convective cores, may yield locally severe downdraft gusts, some perhaps reaching 65 kt. ..Edwards/Bentley.. 01/09/2024 Read more View the full article Quote
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