Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jun 11 2023 20:02:26 ACUS01 KWNS 112002 SWODY1 SPC AC 112000 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Sun Jun 11 2023 Valid 112000Z - 121200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON THROUGH TONIGHT ACROSS THE MID-SOUTH AND TN VALLEY REGIONS... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT FROM THE CO FOOTHILLS INTO NORTHERN TX PANHANDLE...AND ACROSS NORTH TX... ....SUMMARY... Severe thunderstorms capable of damaging winds and hail are expected across a broad portion of the Tennessee Valley and Mid-South this afternoon and evening. Severe thunderstorms are also possible across the south-central High Plains and North Texas. ....20Z Update... ....Mid-South/TN Valley... Thunderstorm coverage is still expected to increase this afternoon across the region as ascent from the approaching shortwave trough interacts with the moist and buoyant air mass in place. Effective bulk shear around 30-35 kt will support a mix of multicell clusters/line segments capable of producing damaging winds and large hail. Additional information about this region is available in recently issued MCD #974. ....CO Front Range into the TX Panhandle... Cumulus continues to build across the higher elevations of north-central NM and south-central CO, with a few thunderstorms already in place. The expectation outlined in the previous discussion remains valid, with thunderstorms coming off the terrain into post-frontal upslope environment across the lower elevations. As mentioned in MCD #973, this environment will support high-based supercells with the potential for large hail (with instances near 2 inches) and damaging winds. Weak low-level shear will limit tornado potential but any discrete supercells that become established could pose risk of a tornado as they track eastward into the better air mass across far eastern Colorado/Oklahoma Panhandle. ....TX Big Country into North TX... Thunderstorm development is still expected later this afternoon/early evening in the corridor from SJT northeastward into the Young/Stephens/Eastland county vicinity. Robust buoyancy and shear will support the potential for splitting supercells capable of very large hail and strong downbursts. ....Great Basin... A few strong gusts remain possible across the Great Basin as clusters of high-based thunderstorms move northwestward this afternoon and evening. ...Mosier.. 06/11/2023 ..PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Jun 11 2023/ ....Mid-South/TN Valley region through tonight... Around the southern periphery of a closed midlevel low over the upper Great Lakes, embedded shortwave troughs will move eastward over the lower OH and TN Valleys through early tonight. An associated surface cyclone will likewise develop eastward along and just north of the OH River, as a trailing pre-frontal trough and cold front move southeastward across the Mid-South and southern Plains through tonight. Clouds are fairly widespread as of late morning from the southern Appalachians northward into the OH Valley and westward into the mid MS Valley. A little south of the thicker clouds and surface cyclone track, there is a corridor of stronger surface heating from south central KY into the Mid-South, where temperatures will warm into the 80s with mid-upper 60s dewpoints. These surface conditions beneath midlevel lapse rates of 7-7.5 C/km will drive MLCAPE of 1500-2500 J/kg with minimal convective inhibition. Scattered thunderstorm development is expected by early-mid afternoon in the zone of weak low-level confluence/convergence associated with an embedded midlevel speed max, along the edge of the thicker clouds from central KY into western TN and AR. The moderate-strong buoyancy and midlevel flow near 40 kt will support a mix of multicell clusters/line segments capable of producing damaging winds and large hail. There will be somewhat stronger deep-layer flow/shear and a little greater potential for supercells across the Mid-South later this afternoon/evening. The convection will continue to spread eastward and southeastward across the TN Valley early tonight, with some continued damaging-wind threat. Other scattered thunderstorms could form this afternoon/evening to the west of the thicker clouds across the southern Appalachians. The stronger wind profiles/vertical shear will be west and north of this area through the afternoon, so the primary severe threats will be damaging downburst winds and marginally severe hail this afternoon/evening. Uncertainty increases with eastward extent due to the widespread clouds/rain from northeast GA into western NC and vicinity, and the primary increase in flow/shear will tend to occur after the muted diurnal cycle. ....Southern High Plains through tonight... Post-frontal, upslope flow is established this morning from eastern CO into northeast NM. Though not particularly large, buoyancy will be sufficient for supercells forming and moving eastward off the Raton Mesa, given easterly low-level inflow and relatively long hodographs. Large hail in excess of 2 inches in diameter and severe outflow gusts of 60-70 mph will be the primary severe threats, though an isolated tornado could also occur. Convection will likely persist into the overnight hours, immediately downstream from an embedded mid-upper speed max that will move east-northeastward from AZ to NM. Storm development is much less certain farther south into northeast NM and the TX Panhandle/South Plains. If a storm were to form along the stalled front this afternoon, it would potentially become supercellular with a conditional large hail threat. ....North TX late this afternoon into early tonight... Strong surface heating is underway to the south of a pre-frontal trough and weak cold front that are moving slowly southward across OK. As surface temperatures warm well into the 90s, convective inhibition will diminish and MLCAPE will increase to 3000-4000 J/kg. Low-level flow will remain rather weak, but deep-layer flow will be strong enough to support the potential for a few splitting supercells (given relatively straight hodographs with effective bulk shear of 35-40 kt). Isolated very large hail up to 2.5 inches in diameter and damaging gusts will be the main threat with these storms from late afternoon into early tonight. ....Great Basin this afternoon/evening... Embedded speed maxima will rotate northward around the eastern periphery of the midlevel low over southern CA. The ascent attendant to the speed maxima, in concert with daytime heating, will support clusters of high-based storms capable of producing a few strong-severe outflow gusts. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .