SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sat Jul 24 2021 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE OHIO VALLEY INTO THE NORTHEAST...AND ALSO ACROSS PARTS OF SOUTH DAKOTA... ...SUMMARY... Thunderstorms with isolated wind-damage potential are possible across parts of the Ohio valley and Northeast, and also across parts of South Dakota, Sunday afternoon and evening. ...Ohio Valley into the Northeast... A belt of 30-40 kt west-northwesterly midlevel flow will largely remain in place from the northern Plains into the Northeast on Sunday, along the southern periphery of a deep mid/upper-level trough covering much of eastern Canada. An embedded midlevel shortwave trough is forecast to move across New England during the morning and early afternoon, with another shortwave trough glancing northern New England Sunday night, but otherwise large-scale ascent may remain weak from the OH Valley into the Northeast through much of the period. As a result, coverage of robust afternoon thunderstorm development remains uncertain. However, a few strong storms will be possible along/ahead of a weak surface boundary sagging into the region. Effective shear of 20-30 kt will support the potential for weakly organized cells/clusters, with isolated damaging wind possible where low-level lapse rates can steepen during the afternoon. ...South Dakota... Isolated thunderstorms may develop across portions of South Dakota by late afternoon, as MLCINH is removed by strong surface heating/mixing. Potential areas for initiation include a weak surface trough across western SD, and a weak surface boundary near the ND/SD border. Despite rather limited low-level moisture, MLCAPE is expected to rise into the 500-1000 J/kg range as temperatures increase to near or above 100F in some locations. Modest west-northwesterly midlevel flow will support effective shear of 25-35 kt, sufficient for at least transient storm organization. A very warm and deeply-mixed boundary layer will support an isolated severe-wind risk with the strongest storms and outflows. ...Southwest... As a midlevel trough continues to drift westward across Arizona, moderate instability and modestly enhanced midlevel flow/deep-layer shear may again support a few organized storms across portions of the Southwest. The areal extent of the more favorable environment is expected to be smaller than previous days, so no probabilities have been included at this time. However, a few strong cells/clusters cannot be ruled out, especially from northwest AZ/southwest UT into southern NV and perhaps southeast CA. ..Dean.. 07/24/2021 Read more LIVE: spc.noaa.gov
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