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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.

Thursday, October 21, 2021

SPC Oct 21, 2021 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Thu Oct 21 2021 Valid 211300Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL/SOUTHERN APPALACHIANS AND UPPER OHIO RIVER VALLEY... ...SUMMARY... Thunderstorms associated with isolated strong wind gusts will be possible mainly this afternoon across parts of the southern and central Appalachians into the Upper Ohio River Valley. Isolated storms capable of marginally severe hail and strong gusts may also occur over far West Texas. ...Upper Ohio Valley and central and southern Appalachians... A compact upper low/shortwave trough centered near the Illinois/Wisconsin border early this morning will continue generally eastward toward the Lower Great Lakes through evening. A cyclonically curved belt of moderately strong westerlies will accompany this shortwave trough, with weak height falls and 35-40 kt mid-level westerlies expected as far south as the southern Appalachians. Widely scattered showers and some thunderstorms are ongoing early today across parts of the Tennessee Valley/southern Appalachians, as well as across Ohio. Increasing thunderstorm coverage and intensity, at least to some degree, is expected into the afternoon, especially near an east/southeastward-advancing cold front. This front will intercept only a modestly moist/unstable environment across the Ohio Valley where forcing for ascent/vertical shear will be strongest, while convergence will be weaker where a more unstable environment will reside this afternoon across the Tennessee Valley and windward portions of the southern Appalachians. Regardless, moisture/instability will generally be adequate in the presence of ample effective shear (45-55 kt) to support some semi-organized/fast-moving storm clusters (perhaps with some initial weak supercell characteristics) this afternoon. Localized damaging winds could occur with some of these storms before updraft/downdraft intensities wane this evening. ...Far West Texas... A relatively moist air mass in conjunction with orographic influences/differential heating should contribute to at least isolated thunderstorm development in vicinity of the Davis Mountains this afternoon. Steep lapse rates, moderate buoyancy, and modest effective shear (25-30 kt) may support some locally severe storms capable of hail and strong wind gusts through early evening. ..Guyer/Leitman.. 10/21/2021 Read more LIVE: