Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Fri Jul 21 2023 18:09:00 ACUS01 KWNS 211932 SWODY1 SPC AC 211930 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Fri Jul 21 2023 Valid 212000Z - 221200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHEAST...FAR EASTERN NEW YORK INTO SOUTHERN NEW ENGLAND...AND THE SOUTHERN HIGH PLAINS... ....SUMMARY... Severe thunderstorms capable of wind damage and some hail are expected across parts of the the Mid-South and Tennessee Valley to the Southeast States. Additional severe storms remain possible across portions of the Northeast and southern/central High Plains. ....20Z Update... Main change with this update was to expand severe probabilities northward across parts of the TN Valley based on the track of a small but intense MCS moving generally eastward across western TN and far northern MS. Severe/damaging winds will remain the primary threat with this convection across middle/eastern TN into northern AL/GA through the rest of the afternoon and into this evening. See recently issued Mesoscale Discussion 1666 and Severe Thunderstorm Watch 536 for more details on the short-term threat across this area. The potential for development farther south into central MS/AL/GA remains less certain, but still possible. No changes have been made to the risk areas across parts of the Mid-Atlantic/New England and the southern/central High Plains. ...Gleason.. 07/21/2023 ..PREV DISCUSSION... /ISSUED 1116 AM CDT Fri Jul 21 2023/ ....AR into the Southeast States... A large MCS that tracked across southern OK last night is now over northern/central AR. This system and its attendant MCV will move into western TN this afternoon, where sufficient heating and a very moist air mass will support the potential for re-intensification. If this scenario occurs, locally damaging wind gusts would be the main concern. To the southeast of the MCS, a weak surface boundary extends across southeast AR into portions of MS/AL/GA. A very unstable air mass will become established this afternoon along this axis, where scattered thunderstorm development is expected. MLCAPE values around 3000 J/kg will combine with winds in the 5-7km layer around 30 knots to pose some risk of damaging wind gusts in the stronger cells. The risk of wind damage will increase later this afternoon if sufficient thunderstorm coverage can result in more organized outflows. ....New England... An upper trough is moving across the northeast states today, with an associated cold front currently extending across parts of eastern NY/PA. Clouds have been clearing ahead of the front across western New England, where temperatures will rapidly warm into the 80s. Ample low-level moisture is present from southern VT/NH southward, where upper 60s/lower 70s dewpoints will yield afternoon MLCAPE values of 1500-2000 J/kg. Forecast soundings show sufficient deep layer shear for a few organized/rotating storms capable of strong/damaging wind gusts and perhaps hail for a few hours this afternoon. ....Northeast NM... Weak easterly low-level upslope flow is present today over northeast NM, helping to transport 60s dewpoints westward toward the higher terrain. Thunderstorms are expected to form in the mountains near Raton and drift southeastward through the afternoon. Steep low-level lapse rates and 30-40 knots of effective shear will promote the development of a few supercells capable of large hail and damaging wind gusts. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .