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Friday, October 15, 2021

SPC Oct 15, 2021 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Fri Oct 15 2021 Valid 151300Z - 161200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF ARKANSAS ACROSS THE OHIO VALLEY INTO WESTERN NEW YORK... ...SUMMARY... Isolated severe gusts and hail, along with a marginal tornado threat, are expected today from parts of Arkansas across the Ohio Valley into western New York. ...Synopsis... In mid/upper levels, a progressive synoptic-scale trough will cross the central CONUS through the period, from its present position over the High Plains. By 12Z tomorrow, the trough should arc across Lower MI to the lower Ohio Valley and southwestern AR. At the surface, 11Z analysis showed an occluded/cold front from southwestern QC across Lake Ontario, northern OH, through a weak low near HUF, another near HRO, another between MWL-ADM, then southwestward across the TX Big Bend and across eastern Chihuahua. A warm front was drawn from central/northern OH southwestward over northern/central MS. The warm front should move northeastward over the inland Mid-Atlantic and lower Great Lakes through the period. By 00Z, the northern low should deepen and move to Lake Erie, with cold front southwestward over western portions of OH/KY/TN, northwestern MS, and southeast to deep south TX. By 12Z, the cold front should extend from Lake Ontario over western PA, WV, northeastern TN, northern GA, eastern AL, and the north-central/ west-central Gulf. ...AR to western NY... Episodes of scattered frontal and prefrontal thunderstorms are expected today up and down this corridor, offering damaging to severe gusts, potential for a few tornadoes, and isolated, marginally severe hail. As the mid/upper trough moves eastward, expect falling heights aloft, strengthening (but largely front-parallel) mid/upper winds and deep shear, as well as shots of DCVA within the southwest flow. A northeastward shift of the strongest part of the LLJ also should occur, toward OH/PA and western NY by late this afternoon, with accompanying warm advection and moisture advection/transport from the higher-theta-e air mass now over the lower Ohio Valley and Mid-South. Also, the ongoing Ozarks activity that started last night west-southwest of OKC has generated a well-defined MCV initially near FLP. This feature should move east-northeastward to northeastward toward the PAH area and perhaps beyond, across parts of KY and up the lower Ohio Valley. All those factors, as well as areas of warm-sector diurnal heating/ destabilization in cloudiness gaps, will support thunderstorm development today. Activity largely should assume quasi-linear to clustered configurations, though sufficient deep shear will exist to support supercell potential -- either embedded in a line or in the warm sector. Outflow/differential-heating zones will be the most probable foci for warm-sector potential. Despite the rich low-level moisture, modest midlevel lapse rates should help to limit MLCAPE to the 500-1000 J/kg range from KY-NY, and 1000-1500 J/kg range around the Mid-South and AR where stronger heating and greatest moisture are expected. Wind profiles will be mostly unidirectional, except for some better-curved hodographs under the northeastern LLJ segment or in mesoscale areas where the wind profile is altered by a passing MCV. ..Edwards/Leitman.. 10/15/2021 Read more LIVE: spc.noaa.gov
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