Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 26 2023 01:01:25 ACUS01 KWNS 260101 SWODY1 SPC AC 260059 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 PM CDT Tue Jul 25 2023 Valid 260100Z - 261200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-ATLANTIC AND FROM THE CENTRAL AND NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY... ....SUMMARY... Thunderstorms associated with isolated large hail and wind damage will be possible this evening in the northern and central Plains, upper Mississippi Valley, and Mid-Atlantic. A few storms with strong wind gusts could also occur in parts of the northern High Plains. ....Northern and Central Plains/Upper Mississippi Valley... A large mid-level anticyclone, evident on water vapor imagery, is located from the Desert Southwest into the southern and central Plains. To the north of this feature, mid-level flow is west-northwesterly across the north-central U.S. A shortwave trough appears to be moving through the flow in the northern Plains. At the surface, a cold front is moving eastward across the central Dakotas, extending southward into west-central Nebraska. A moist and unstable airmass is located ahead of the front, where surface dewpoints are mostly in the 70s F, and strong instability is analyzed by the RAP. Scattered thunderstorms are ongoing in eastern North Dakota, with more isolated convection located across east-central South Dakota and north-central Nebraska. Thunderstorm coverage is expected to gradually expand across the northern Plains this evening. MCS development will be possible across the southern half of Minnesota and across eastern South Dakota by late evening. This convection will move southeastward into the upper Mississippi Valley tonight. The strongest instability is currently analyzed by the RAP from eastern Nebraska into eastern South Dakota, where MLCAPE is estimated to be between 4000 and 5500 J/kg. In addition, the WSR-88D VWP at Aberdeen has 0-6 km shear near 40 knots, with directional shear in the low-levels. This, combined with 700-500 mb lapse rates of 7.5 to 8.0 C/km will be favorable for supercells with large hail, mainly from the eastern Dakotas into north-central and northeast Nebraska. A wind-damage threat is also expected to continue along this corridor, where low-level flow will steadily strengthen this evening. The wind-damage threat will likely increase as an MCS develops and moves southeastward into southwest Minnesota and northwest Iowa late this evening. Isolated severe storms will also be possible in parts of the central High Plains, along the western edge of the strongest instability. The severe threat may persist into the overnight period across parts of the upper Mississippi Valley, along the expected track of the MCS. ....Mid-Atlantic... An upper-level trough is evident on water vapor imagery over the central Appalachians Foothills. Ahead of this feature, a moist airmass is located along much of the Eastern Seaboard. Across the Mid-Atlantic, surface dewpoints are maximized and primarily in the 70s F. This is contributing a pocket of moderate instability from eastern North Carolina northward into southern Maryland, where the RAP has MLCAPE in the 2000 to 2500 J/kg range. Scattered thunderstorms are ongoing along a gradient of instability from northern Virginia into Maryland. The latest WSR-88D VWP in eastern Maryland has 0-6km shear around 40 knots with substantial speed shear mostly in the mid-levels. In addition, 0-3 km lapse rates are estimated by the RAP to be around 7 C/km. This should be favorable for multicells with wind-damage potential. The threat is expected to continue for another hour or two as cells move eastward toward the coast. ....Northern High Plains... A mid-level anticyclone is located from the Desert Southwest into the southern and central Plains. Along the northern edge of this feature, mid-level flow is westerly. A subtle shortwave trough, evident on water vapor imagery, is currently moving eastward across central Montana. Isolated thunderstorms are ongoing ahead of the trough in eastern Montana. Although instability in this area is generally weak, lift associated with the trough should continue to support thunderstorm development this evening. Steep low to mid-level lapse rates and moderate deep-layer shear may be enough for a marginal wind-damage threat with the stronger multicells. ...Broyles.. 07/26/2023 $$ = = = 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) .