Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 12 2024 19:54:05 ACUS01 KWNS 121954 SWODY1 SPC AC 121952 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Thu Sep 12 2024 Valid 122000Z - 131200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN MONTANA AND WESTERN NORTH DAKOTA... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHEAST... ....SUMMARY... A few tornadoes are possible today from northern Florida to north-central Alabama. Scattered large hail and severe wind gusts (some significant) are expected across eastern Montana into western North Dakota this afternoon through early/mid-evening. ....20z... The D1 Convective Outlook remains on track with no updates needed. A narrow corridor of tornado risk associated with Tropical Depression Francine and the mid/upper low across the southeast will continue across central/southern Alabama this afternoon and evening. See MCD#2061 for more information. Across the northern Great Plains, potential for significant damaging winds will increase through the afternoon and evening as ongoing convection across Montana and Wyoming increases in coverage and tend to grow upscale through the evening. See previous discussion for more information on this threat. ...Thornton.. 09/12/2024 ..PREV DISCUSSION... /ISSUED 1138 AM CDT Thu Sep 12 2024/ ....Northern Great Plains including eastern MT/western ND... Have upgraded portions of eastern Montana and western North Dakota for a heightened/focused potential for severe storms capable of large hail and potentially significant-caliber severe wind gusts later this afternoon through around mid-evening. Strong-severe thunderstorms are expected, along and behind the front, as early as early/mid-afternoon, with the most probable severe potential arising from activity moving north-northeastward from northern Wyoming and far southern Montana. High-based supercells and multicells are possible, offering large hail and severe wind gusts. These storms may aggregate and grow upscale into one or two bowing clusters, racing north-northeastward accompanied by a swath of better-organized, potentially significant (65+ kt) gust potential. This scenario will be supported by trough-related cooling mid-level temperatures and steep low/mid-level rates atop a modestly moist boundary layer, as the exit region of a strong upper-level jet overspreads the region. MLCAPE of 500-1200 J/kg and 45-55 kt effective-shear magnitudes will support the severe potential including fast-moving and relatively long-lived storms into western North Dakota. The near-surface airmass over the central Dakotas should stabilize with time and eastward extent tonight, limiting duration and eastward shift of the threat. ....Southeast... Current Tropical Depression Francine is forecast to continue moving generally northward over Mississippi, and to lose definition as it interacts more closely with the mid/upper-level low. Associated deep-layer winds will continue to weaken, but low-level shear will remain favorable through most of the day, well to the east-southeast of its center. A destabilizing airmass along and south of the warm/marine front will support a continued, slow inland shift of supercell potential amid enlarged hodographs. The favorable environment will be bounded on the west by a dry slot and veering low-level flow, on the northeast by more stable air in heavy precip north of the front, and on the south by a gradual weakening of low-level winds and shear as the cyclone center pulls away and fills. In the favorable corridor, where inflow parcels are surface-based, expect effective SRH in the 200-500 m2/s2 range, very rich moisture, low LCL, and weak MLCINH. In the shorter term, a tornado threat may persist this afternoon across northern Florida, while potentially increasing later this afternoon through early evening near the warm front across southern into central Alabama. $$ = = = 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) .