Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 11 2024 12:57:32 ACUS01 KWNS 111257 SWODY1 SPC AC 111255 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Thu Jul 11 2024 Valid 111300Z - 121200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN ARIZONA... ....SUMMARY... Severe thunderstorm gusts are possible over parts of southern Arizona from midafternoon into early evening. ....Synopsis... In mid/upper levels, the overall pattern will change little through the period, with mean ridging in the West, and troughing over the Great Lakes and vicinity. The persistent anticyclone will remain over the Great Basin, with some deamplification of ridging to its north leading to more-zonal flow across the northern tier of states from WA-ND. A weak shortwave trough -- apparent in moisture-channel imagery over parts of central/eastern MT -- should move slowly east-southeastward across the northern High Plains today amid difluent flow. Meanwhile and downstream, a pronounced shortwave trough now over parts of WI/IL/IA should eject northeastward over the Upper Great Lakes and weaken, while smaller/upstream perturbations help to maintain the mean trough. Both the low/middle-level remains of TC Beryl, and a closely associated shortwave trough of midlatitude origins, should shear northeastward across southern QC, the lower St. Lawrence Valley, and northern New England, weakening considerably. At the surface, 11Z analysis showed a low near the NH/QC border with slow-moving, weakening cold front across western New England, the coastal Mid-Atlantic/Carolinas, southern GA, and FL Panhandle, becoming quasistationary along the northwestern Gulf Coast. This front should continue weakening near or just east of its present position through the period, over the Northeast, and also weaken over the Gulf Coast and southern Atlantic Coast States. Enough low-level shear exists over parts of ME today to support a conditional supercell potential, but strength/coverage/longevity are in question due to weakness of both instability and lift. Elsewhere, a lee trough analyzed on that chart over eastern parts of MT/WY/CO should remain over the central/northern High Plains today, with some eastward drift possible. ....AZ... Widely scattered to scattered thunderstorms are expected to develop this afternoon, over the Mogollon Rim and smaller mountain ranges to the south. That will occur as strong insolation at those higher elevations preferentially removes MLCINH, in the presence of generally greater low-level moisture than previous days. Some strengthening of flow aloft is expected over this region, around the southeastern rim of the anticyclone. This will support convective motion off the Rim (and small mountain ranges to its south), then atop well-heated/deeply mixed boundary layers of the desert floor. Isolated strong-severe gusts are possible from the relatively early, more-discrete activity. With the lower-elevation boundary layers being very deep (surface to around 600 mb), but enough moisture maintained through mixing to keep surface-based buoyancy (MLCAPE in the 500-1000 J/kg range), expect some aggregation of outflows with additional development atop those -- especially over southeastern AZ. The net result should be both translation and developmental propagation of convection southwestward to and across the international border, with swaths of strong-severe gusts possible. ....Northern High Plains... Isolated to widely scattered, high-based thunderstorms are expected to form near the lee trough, where both relatively maximized convergence and strong surface heating should contribute to enough lift for convective initiation. The main concern up and down the corridor should be damaging to severe gusts, given the deeply mixed subcloud layer and ample downdraft-acceleration opportunity that will afford. Isolated severe hail also may occur, amidst enough deep-layer shear for some organized thunderstorms (effective-shear magnitudes of 30-40 kt). Lack of greater moisture and buoyancy will be a limiting factor for coverage and intensity of convection, which should diminish rapidly after dark. ...Edwards/Bentley.. 07/11/2024 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .