SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1119 AM CDT Mon Aug 02 2021 Valid 021630Z - 031200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF CENTRAL OREGON... ...SUMMARY... Strong to isolated severe downburst winds will be possible over central Oregon this afternoon and early evening. ...Synopsis... Upper ridging is expected to persist across the western CONUS through the day while mid-level troughing/broad cyclonic flow will prevail across the central and eastern U.S. At the base of the mid-level eastern trough, scattered to numerous thunderstorms are already underway across the south-central/southeast U.S. With continued surface heating, more widespread thunderstorm development is expected through the afternoon. Similarly across the Interior West, scattered to numerous thunderstorms are expected to develop with increasing buoyancy given the presence of ample monsoonal moisture. In central Oregon, high-based thunderstorm development is expected atop a deep, dry boundary layer later this afternoon and evening. A few of the stronger storms may be accompanied by strong, gusty winds. ...Central Oregon... The latest guidance consensus (including high-resolution deterministic and ensemble members) continue to show pulse updraft and occasional multicellular cluster development by early afternoon atop the southern Cascades. These storms will form along the western periphery of the upper ridge, amid 25-35 kt southwesterly mid-level flow. The latest guidance continues to portray inverted-v vertical thermodynamic profiles across the region as the dry boundary layer is expected to mix up to 600-500 mb. Given 0.75-1.0 inch precipitable water values and 9.5 C/km 0-3km lapse rates driven by the deeply mixed boundary layer, adequate evaporative cooling may take place to support a few damaging gusts, prompting the continuation of the Marginal Risk. ...Southeast U.S... Scattered to numerous thunderstorms are developing in proximity to and ahead of an MCV over MS. With continued heating along a diffuse baroclinic zone across the Southeast, more widespread thunderstorm development is likely in advance of the MCV. Given very weak troposheric flow and associated vertical wind shear across the region, convection is expected to remain generally pulse-cellular in nature, with some clustering/chaotic cold pool mergers likely. Given the presence of 2000-3000 J/kg MLCAPE (driven primarily by deep low-level moisture), a couple of wet downbursts/damaging gusts are possible. However, the damaging gust threat still appears too sparse/disorganized to support the addition of a Marginal Risk. ..Squitieri/Mosier.. 08/02/2021
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