Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 17 2023 07:31:14 ACUS03 KWNS 170731 SWODY3 SPC AC 170730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Mon Jul 17 2023 Valid 191200Z - 201200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS...MID MISSOURI VALLEY...UPPER MISSISSIPPI VALLEY AND OHIO VALLEY... ....SUMMARY... Thunderstorms associated with marginally severe wind gusts and hail will be possible on Wednesday from the central Plains to the upper Mississippi Valley, and in the Ohio Valley. ....Central Plains/Mid Missouri and Upper Mississippi Valleys... A positively-tilted upper-level trough will move across the northern Plains on Wednesday, as a cold front advances southeastward across the northern Plains towards the central Plains and Upper Mississippi Valley. Ahead of the front, surface dewpoints in the mid 60s F will likely contribute to moderate instability in some areas by afternoon. Isolated to scattered thunderstorms are forecast to initiate near the front and move southeastward across the region during the afternoon and evening. The latest model runs vary considerably concerning how much instability will develop ahead of the front by afternoon. The NAM suggests that a moderately instability will be in place by midday from central Nebraska northeastward into south-central Minnesota, while the latest run of the ECMWF has a more weakly unstable airmass along that corridor. Variance within the model solutions introduces considerably uncertainty concerning a severe threat on Wednesday. The current thinking is that the NAM may be overdone concerning instability. The models also vary considerably on convective coverage, with the NAM again being more aggressive. If the NAM more closely verifies, then the airmass ahead of the front would be moderately unstable with 0-6 km shear mostly in the 40 to 45 knot range. This would be favorable for a severe threat in most areas ahead of the front during the late afternoon and early evening. Due to this possibility, a marginal risk area has been added to much of the central Plains, mid Missouri Valley and upper Mississippi Valley. ....Ohio Valley... Westerly flow at mid-levels will be in place across the Great Lakes and Ohio Valley on Wednesday. A subtle shortwave trough is forecast to approach the Ohio Valley during the day. At the surface, a moist airmass will be located across most of the Ohio and Tennessee Valleys, with an east-to-west gradient of instability from southern Illinois into northeastern Kentucky. This will likely be a favored corridor for convective development Wednesday afternoon. NAM forecast soundings near this gradient at 00Z/Thursday have MLCAPE near 1500 J/kg, and 0-6 km shear around 35 knots. The wind profile is forecast to be veered in the low-levels with most of the speed shear located above 700 mb. This would support an isolated severe threat, and the stronger multicell line segments could have a potential for wind damage during the mid to late afternoon. ...Broyles.. 07/17/2023 $$ = = = 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .