SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Mon Aug 30 2021 Valid 301300Z - 311200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO TONIGHT FOR PARTS OF THE NORTH CENTRAL GULF COAST AND THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Some tornado threat continues across the central Gulf States with remnants of Ida. Severe storms with very large hail and damaging winds are possible across parts of the northern and central Plains. ...Tropical Storm Ida today into tonight... Weakening Tropical Storm Ida will continue moving slowly northward over southwest and central MS, and then gradually turn northeastward tonight. A large shield of rain has limited buoyancy inland from the coast, and a gradient in buoyancy will likely be maintained today along the east edge of the more persistent rain. Broken convective bands will continue in this buoyancy gradient from the MS coast into southwest AL today, with the stronger flow and low-level shear from the west overlapping the west edge of the somewhat larger buoyancy toward the AL coast. Though tornado production has been muted thus far, likely as a result of the weak inland buoyancy, there will be some potential for a bit more destabilization inland today across southwest AL as surface heating occurs in clouds breaks and Ida moves slowly northward. Thus, a couple of tornadoes still remain possible with supercells along and just ahead of the main north-south convective band. The tornado threat becomes more conditional with northeastward extent and into tonight across AL, though low-level shear will be strong enough to maintain a non-zero tornado threat overnight. ...Central Plains today into tonight... Subtle midlevel speed maxima will move southeastward over parts of the central Plains as a shortwave ridge begins to amplify upstream over the High Plains (east of a deepening trough over the Pacific Northwest). A slow-moving baroclinic zone, oriented northwest-southeast, will be maintained from southwest SD to eastern NE. This front will likely be the focus for thunderstorm development, potentially today in the zone of ascent along the boundary, and into tonight as a warm advection increases on the nose of a 30 kt low-level jet. Forecast profiles are characterized by steep midlevel lapse rates (greater than 8 C/km) and MLCAPE of 2000-3000 J/kg, with sufficient hodograph length and curvature for right-moving supercells. Isolated very large hail (2.5 inch diameter or larger) will be possible with supercells along the boundary, and an isolated tornado or two may also occur where low-level shear is stronger and temperature-dewpoint spreads are lower along the boundary. There is also the potential for storms to evolve into a cluster or two this evening into tonight, with an attendant threat for damaging winds and large hail. ...Northeast this afternoon... The southern extent of a midlevel low over QC will move over northern New England today, helping drive a cold front eastward during the afternoon. Though midlevel lapse rates will be rather poor, there may be enough buoyancy and midlevel flow to support broken bands of storms along the front, with some potential for downward momentum transfer and isolated tree damage. The southwest extent of any semi-organized wind threat is fairly uncertain, given the modest thermodynamic profiles and gradual decrease in midlevel flow/shear with southwest extent across New England. ..Thompson/Broyles.. 08/30/2021 Read more LIVE: spc.noaa.gov
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