Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 16 2025 08:58:40 ACUS48 KWNS 160857 SWOD48 SPC AC 160856 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0356 AM CDT Sat Aug 16 2025 Valid 191200Z - 241200Z ....DISCUSSION... ....Tuesday/Day 4 and Wednesday/Day 5... A mid-level ridge will build across the Rockies and northern High Plains during the middle part of the week. At the surface, a front will advance slowly southward into the lower Missouri and mid Mississippi Valleys. A post-frontal airmass will remain over the upper Mississippi and Great Lakes region. On the southern and western periphery of this airmass, moderate instability is forecast to develop each afternoon. Limited large-scale ascent is expected to keep convective coverage isolated. In spite of relatively weak deep-layer shear along much of the instability corridor, steep low to mid-level lapse rates will be in place and could be enough for a marginal severe threat in areas that destabilize the most. ....Thursday/Day 6 and Saturday/Day 8... Mid-level zonal flow is forecast to develop on Thursday over much of the north-central and northwestern U.S., as a ridge moves southeastward into the western Great Lakes. A pocket of moderate instability is forecast to develop ahead of a cold front on Thursday in the northern Plains. Limited large-scale ascent should keep convective coverage isolated. Although deep-layer shear is forecast to be modest, any cell that can develop and persist near the stronger instability in the late afternoon and early evening could obtain an isolated severe threat. On Friday an Saturday, a cold front is forecast to move southeastward across the north-central U.S. Near and ahead of the front, isolated thunderstorms will be possible each afternoon from the upper Mississippi Valley into the Great Lakes region. The combination of instability and shear could be sufficient for an isolated severe threat. However, considerable uncertainty exists at this range in the forecast. ...Broyles.. 08/16/2025 = = = 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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .