SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Aug 21 2021 Valid 211630Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT BASIN/NORTHERN INTERMOUNTAIN WEST AND SOUTHERN PLAINS/DEEP SOUTH... ...SUMMARY... Isolated severe thunderstorms are possible this afternoon and evening across parts of the southern Plains and Southeast States, and in the northern Intermountain West. Locally damaging winds are the primary risk. ...Southern Plains to Southeast States... Under the influence of a cyclonic belt of moderately strong winds aloft, scattered clusters of southeastward-moving storms are expected to develop/intensify this afternoon across parts of the Tennessee Valley/southern Appalachians into South Carolina. Locally damaging winds will be possible with the strongest storms. Aided by strong heating and a weak surface low/effective boundary, other widely scattered storms are expected to develop late this afternoon across the Texas Panhandle and western Oklahoma. These storms may pose an isolated severe hail risk aside from locally damaging winds. ...Great Basin/northern Intermountain West... A southeastward-digging shortwave trough over the Pacific Northwest will turn more eastward and move over the northern Intermountain West through tonight. As sampled in regional 12Z upper-air data, a seasonally strong belt of mid-level westerlies will overspread northern parts of Nevada/Utah as well as eastern Idaho, southern Montana and Wyoming coincident with an eastward-moving front. Widely scattered to scattered high-based thunderstorms are expected to develop and increase this afternoon across the region. Boundary-layer heating/mixing and resultant inverted-v profiles in conjunction with the aforementioned moderately strong winds at the top of the boundary layer may support strong/locally severe-caliber wind gusts, potentially along with a couple instances of marginally severe hail. ...Long Island/southern New England... Reference the National Hurricane Center for the latest forecast details for Hurricane Henri. Related to Henri, current thinking is that any brief tornado/thunderstorm-related wind potential will not occur through tonight (period ending 12Z Sunday). ..Guyer/Lyons.. 08/21/2021 Read more LIVE: spc.noaa.gov
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