SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0148 PM CST Sat Feb 27 2021 Valid 272000Z - 281200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN OKLAHOMA TO WESTERN KENTUCKY... ...SUMMARY... Isolated strong to severe thunderstorms remain possible from eastern Oklahoma to western Kentucky this evening and overnight. ...20Z Update... No appreciable changes have been made to the ongoing forecast. Elevated storms are expected to continue increasing in coverage this afternoon/evening across parts of eastern OK into AR as low-level warm advection strengthens in tandem with a south-southwesterly low-level jet. This activity should eventually spread into southern MO and the Mid-South tonight while posing an isolated threat for marginally severe hail and perhaps a strong wind gust or two. Generally weak instability should tend to limit the overall severe threat, with convection remaining generally elevated. ..Gleason.. 02/27/2021 .PREV DISCUSSION... /ISSUED 1014 AM CST Sat Feb 27 2021/ ...Synopsis... A large-scale trough across the northern Rockies into the Great Basin will continue to amplify and dig into the Four Corners today. As this occurs, a lee trough/cyclone is expected to develop within the southern/central High Plains. The rather diffuse cyclone will progress to the northeast into the upper-Mississippi Valley region by tomorrow morning. While height falls ahead of the trough will not be overly strong, southerly low-level winds will increase along with the trough/cyclone and ahead of a southeastward moving cold front with accompanying warm front advancing northward in the Mid-South. ...Eastern Oklahoma into Western Kentucky... Moisture return should continue to increase this afternoon and evening across parts of eastern Oklahoma. Scattered storms are expected to develop near the intersecting cold and warm fronts in the vicinity of Fort Smith, AR and points southeastward. This morning's observed regional soundings show mid-level lapse rates of 7-8 C/km. With strong deep-layer flow and MUCAPE near 1000 J/kg, large hail will be possible with these elevated storms. A low-end risk for damaging wind gusts will also exist given the relatively shallow stable near-surface layer. Farther east and north, deep-layer flow will be similarly strong, but these areas will be farther removed from the steeper mid-level lapse rates, reducing buoyancy. A risk for marginally severe hail and damaging wind gusts will still exist. Towards tomorrow morning, forecast soundings do indicate that low-level theta-e advection will allow ongoing storms to become near surface-based meaning the threat for damaging wind gusts may be maximized late in the period.
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