Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1232 AM CDT Mon Jun 29 2020 Valid 291200Z - 301200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH PLAINS...UPPER MISSISSIPPI VALLEY AND IN SOUTH CAROLINA... ...SUMMARY... Isolated severe thunderstorms with hail and marginally severe wind gusts will be possible across parts of the northern High Plains this afternoon and evening. A few marginally severe storms will also be possible across parts of the Upper Mississippi Valley and in South Carolina. ...Northern High Plains... An upper-level low will move slowly across the northwestern U.S. today as south to south-southwesterly mid-level flow remains across the northern High Plains. At the surface, a trough will deepen across the northern High Plains. A capping inversion will be in place along the surface trough during the day limiting convective development. But during the early evening, increasing low-level convergence and a weakening cap should be enough for scattered thunderstorm development. The greatest concentration of storms should be in western North Dakota where MLCAPE is forecast to reach the 2000 to 3000 J/kg range. Storms will develop along the surface trough and move north-northeastward along a sharp north-to-south gradient of instability. Forecast soundings along this gradient of instability at 00Z/Tuesday show 0-6 km shear in the 25 to 35 kt range. This suggests that the environment will support severe multicells, with the main threat being for marginally severe damaging wind gusts and hail. ...Upper Mississippi Valley... An upper-level trough will move north-northeastward across the Upper Mississippi Valley today. The southern extension of the trough will be in Wisconsin where the airmass will be very moist and unstable by afternoon. MLCAPE is forecast to reach the 3000 to 4500 J/kg range by RAP forecast soundings. Thunderstorms appear likely to develop along the eastern edge of the strongest instability from north-central Wisconsin south-southeastward into northern Illinois. Although deep-layer shear is forecast to remain relatively weak, the instability along with steep low-level lapse rates may be enough for a marginal wind damage threat during the afternoon. ...South Carolina... A surface trough will deepen today along the coast of the Carolinas. A moist airmass will be in place across South Carolina where moderate instability should develop by afternoon. Convection is expected to initiate in the higher terrain of the southern Appalachians and move southeastward into the lower elevations of central South Carolina during the mid to late afternoon. Although deep-layer shear is forecast to be relatively weak, the instability combined with steep low-level lapse rates may contribute to a marginal wind damage threat. ..Broyles/Bentley.. 06/29/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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