Administrators NorthGeorgiaWX Posted September 30 Administrators Share Posted September 30 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0737 AM CDT Mon Sep 30 2024 Valid 301300Z - 011200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected today, though a few strong storms may affect central/eastern North Carolina. ...Synopsis/Discussion... The main belt of mid/upper-level, midlatitude westerlies will continue to traverse the northwestern/north-central CONUS and central/southwestern Canada, buckled cyclonically around a prominent synoptic trough now located from eastern SK to central MT and western WY. This trough should phase with another now over central mainland Arctic Canada by the end of the period, resulting in a 500-mb low over southeastern Nunavut, with trough trailing over western Hudson Bay, northwesternmost ON, MN, and IA. Strongly difluent flow aloft will take shape southeast of the trough, across the Mississippi Valley, the Great Lakes from Michigan/Huron on down, the Ohio Valley, and much of the Appalachians. As that occurs, a longstanding, filling, weakening low now over southwestern WV will devolve today to an open-wave trough, losing amplitude rapidly and drifting eastward over the central Appalachians through the period. Part of a basal shortwave trough/vorticity lobe -- now apparent in moisture-channel imagery over eastern TN -- will eject eastward across northern NC and southern VA from this afternoon through tonight. At the surface, 11Z analysis showed a quasistationary front across northern SC to just south of the southern Outer Banks, extending from a triple-point low near CAE. This boundary should shift northward over central/eastern NC through the day. Meanwhile, a cold front -- related to the strong northern-stream trough -- was drawn from central/southern MB across southern ND, central SD, northwestern NE, and southern WY. This front should sweep across most of the Great Plains and upper Mississippi Valley through the period, reaching northern Lower MI, IL, southwestern MO, southern OK, and the TX South Plains by 12Z. ...Central/eastern NC... Widely scattered showers and thunderstorms are expected to develop this afternoon over the Piedmont and coastal plain, in an environment characterized by rich boundary-layer moisture (surface dewpoints commonly in upper 60 to mid 70s F) very weak ambient MLCINH easily removed by diurnal heating, but weak mid/upper-level lapse rates. This will result in 500-1200 J/kg MLCAPE over most of the area from he Piedmont to the Sounds, beneath a belt of sufficiently strong mid/upper flow to yield around 35-45-kt effective-shear magnitudes. Low-level hodographs over central/eastern NC this afternoon, from model forecast soundings, reasonably show curvature near the frontal zone, but with weak speeds in the lowest couple km that substantially limit SRH and vector shear. However, above 1 km, hodographs are somewhat long and straight, suggesting the potential for low-end supercells amidst the mode common multicellular modes. At this time, forecast shear appears too weak to support an unconditional tornado-threat area, but the scenario will be monitored for any mesoscale enhancement to shear (especially along boundaries) that may introduce such a risk. The gust threat appears subsevere at this time, though localized gusts approaching severe limits cannot be ruled out. ..Edwards/Broyles.. 09/30/2024 Read more View the full article Quote Link to comment Share on other sites More sharing options...
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