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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.

Saturday, June 12, 2021

SPC Jun 12, 2021 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0736 AM CDT Sat Jun 12 2021 Valid 121300Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO EARLY TONIGHT FOR PARTS OF THE SOUTHERN HIGH PLAINS... ...SUMMARY... Damaging winds and large hail will be possible late this afternoon into early tonight across parts of the southern High Plains. More isolated damaging gusts may occur this afternoon/evening in an arc from the South to the middle Mississippi Valley and Lower Michigan. ...Southern High Plains this afternoon into early tonight... As a cold front stalls across the South Plains of TX, low-level upslope flow will establish into eastern NM. This will draw low-level moisture westward, which could be augmented by any lingering influence of the convective outflow this morning from southwest OK into northwest TX. Despite the presence of a midlevel high near El Paso, subtle shortwave troughs will rotate around the periphery of the high, with weak west-northwesterly flow aloft atop the low-level easterly flow. This will result in sufficient deep-layer shear/hodograph length for some supercell potential. Given boundary-layer dewpoints well into the 60s F with strong surface heating beneath steep midlevel lapse rates, large buoyancy (MLCAPE of 3000-4500 J/kg) is expected this afternoon/evening. Storms that form over eastern NM, or along the surface front or residual outflow across the South Plains, will be capable of producing large hail initially. Strong downdraft potential should lead to outflow mergers and some upscale growth, with the potential for damaging outflow winds late this afternoon into early tonight. ...The South into the Mid MS Valley and upper Great Lakes... Within an eastern CONUS upper trough, one embedded shortwave trough is moving slowly southeastward over the southern Appalachians, with MCVs farther west over northern MS and northeast TX. A diffuse frontal zone extends from southern SC across GA/AL/MS, with low-mid 70s boundary-layer dewpoints along and southwest of the diffuse front. This surface boundary and the aforementioned midlevel trough/MCVs will help focus scattered thunderstorm development later this afternoon into this evening, with storms expected to move southeastward or southward. Vertical shear profiles will remain relatively weak and will favor multicell clusters, though occasional wet microbursts can be expected with the strongest storms through this evening. Farther north and in association with a subtle shortwave trough cresting the midlevel ridge, a weak surface cold front will move slowly southeastward to the mid MS Valley and the upper Great Lakes. Boundary-layer dewpoints of 65-70 F and daytime heating ahead of the weak front will support widely scattered thunderstorm development this afternoon into this evening from northern IL into Lower MI. Vertical shear will be a little stronger over Lower MI (effective bulk shear of 25-30 kt), where organized multicells or marginal supercells will be possible. Buoyancy will increase with southward extent, with MLCAPE ranging from 1500 J/kg in Lower MI to 2500 J/kg in IL. Thermodynamic profiles will support the potential for a few wet microbursts and occasional damaging outflow gusts this afternoon into this evening. ..Thompson/Leitman.. 06/12/2021 Read more LIVE: