Subj : DAY2SVR: Nws Storm Predic To : All From : Mike Powell Date : Sun Jul 16 2023 09:24:00 ACUS02 KWNS 160558 SWODY2 SPC AC 160557 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Sun Jul 16 2023 Valid 171200Z - 181200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN PLAINS... ....SUMMARY... A threat for isolated large hail will be possible from Monday evening into the overnight period from south-central South Dakota southeastward into the mid Missouri Valley. A marginal severe threat is also expected in the Ohio Valley Monday afternoon. ....Central and Northern Plains/Mid Missouri Valley... Northwesterly mid-level flow will be in place across the north-central U.S. on Monday as an upper-level ridge moves eastward into the northern High Plains. Ahead of the ridge, a lee trough will develop across northeast Wyoming and east-central Montana. Ahead of this feature, moisture advection will take place across the northern Plains. The airmass will remain capped throughout the day as warm air aloft advects northeastward into the region. By early evening, an instability axis is forecast to setup from southwestern South Dakota southeastward into east-central Kansas. Isolated to scattered storms should initiate during the mid to late evening along the eastern edge of the stronger instability as the low-level jet gradually strengthens. The greatest concentration of storms is expected near the northern edge of the low-level jet, moving southeastward across southern South Dakota and northeastern Nebraska during the early overnight period. NAM forecast soundings at 06Z from Pierre, South Dakota southeastward to Norfolk, Nebraska have MUCAPE near 3000 J/kg, with strong effective shear in the 60 to 70 knot range. This, combined with steep mid-level lapse rates should be favorable for isolated large hail with supercells that remain elevated. The wind-damage threat is expected to remain marginal, and confined to areas near the stronger surface-based instability from southwestern South Dakota southeastward into northeast Kansas. The severe threat should gradually increase during the late evening, persisting through much of the overnight period. ....Ohio Valley... An upper-level trough will move eastward across the Great Lakes and lower Ohio Valley on Monday. At the surface, a cold front is forecast to move southeastward toward the lower Ohio Valley during the day. Ahead of the front, surface dewpoints are forecast mostly in the 60s F. As surface temperatures warm, an east-to-west axis of instability is expected to set up from southern Illinois into northeastern Kentucky. Scattered thunderstorms appear likely to form during the early to mid afternoon along this axis of instability. Although low-level winds are forecast to remain veered, moderate deep-layer shear is forecast. This could be favorable for multicell line segments with isolated wind-damage potential, mainly as low-level lapse rates become steep in the afternoon. ....Montana... An upper-level trough will move eastward across the northwestern U.S. on Monday, as an upper-level ridge exits the region to the east. Ahead of the trough, an axis of instability is expected to develop in central and northern Montana, with isolated to scattered thunderstorms forming along and near the instability axis. Although instability is forecast to remain weak, NAM forecast soundings suggest that 0-6 km shear will be around 40 knots, and 700-500 mb lapse rates will approach 7.5 C/km. This environment would be sufficient for a marginal hail threat. A potential for gusty winds will also be possible. Any severe threat would be concentrated near peak heating as instability maximizes across the region. ...Broyles.. 07/16/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .