Administrators NorthGeorgiaWX Posted July 29 Administrators Posted July 29 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Mon Jul 29 2024 Valid 291300Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND THE MIDWEST/LOWER OHIO VALLEY... ...SUMMARY... Scattered strong to severe storms are expected across parts of the central and northern Plains this afternoon and evening, and also across parts of the Midwest and lower Ohio Valley. ...Northern/central Plains and Upper Midwest... A broad upper trough with multiple embedded shortwaves will again be in place across parts of the northern Rockies into the central/northern Plains today. Steep mid-level lapse rates and strong heating will support moderate to locally strong buoyancy by afternoon across parts of the Dakotas into Nebraska. As MLCINH decreases through the afternoon, most guidance suggests at least widely scattered storm development near a surface trough from the western Dakotas into northwest Nebraska. Effective shear of 35-45 kt will support some threat for supercells, with an attendant threat of large hail (possibly in excess of 2 inches in diameter) and localized severe wind gusts. With time, evolution into one or more outflow driven clusters will be possible, with an increasing threat of damaging/severe gusts (potentially in excess of 75 mph). Longevity for any of these potential clusters into late tonight is uncertain, but some threat for damaging/locally severe gusts could spread into parts of Iowa and southern Minnesota before a more definitive weakening trend occurs. ...Midwest/Lower Ohio Valley to Tennessee Valley/Southeast... An MCS has broadened but generally weakened in the pre-dawn hours across Illinois, roughly spanning the Chicagoland area to St Louis vicinity as of 7am CDT. A relatively complex mesoscale scenario exists across the region today largely attributable to the disposition/impacts of this MCS. While severe-weather potential is apparent across the region, some spatial/temporal uncertainties exist regarding the peak/most-focused severe threat later today. This potential is highlighted by a seasonally strong belt of west-northwesterly winds aloft. While the MCS has generally weakened, and may outpace the primary reservoir of instability from the west, there is some potential that storms intensify this afternoon within a warming/increasingly unstable boundary layer across the lower Ohio Valley vicinity including Kentucky/southern Indiana. Damaging winds gusts could occur. Moderately strong westerly low-level flow will otherwise aggressively modify the remnant post-MCS outflow/airmass, with storm redevelopment possible by late afternoon into the evening within a warm-advection regime. Strong destabilization should generally focus across downstate south-central portions of Illinois/Indiana. Current thinking is that severe storm development may occur by late afternoon potentially initially including the I-70 vicinity/Wabash Valley. Aided by the seasonally strong winds aloft (40 kt effective shear), intense supercells are plausible, with attendant risks for isolated hail and a tornado or two. It is probable that storms will further increase during the evening and continue to pose a severe risk as they persist southeastward toward/across the Ohio River. ...Delmarva and Mid-Atlantic/Northeast States... Strengthening northwesterly mid/upper-level flow will overspread the region on the western periphery of a mid-level cyclone moving northward across New England today. As the boundary layer warms and moderately destabilizes, a few strong storms could develop within this regime during the afternoon, with moderate buoyancy and effective shear of 30-35 kt supporting the potential for isolated damaging gusts and hail. ..Guyer/Grams.. 07/29/2024 Read more View the full article Quote
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