Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 26 2023 13:00:32 ACUS01 KWNS 261300 SWODY1 SPC AC 261259 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Wed Jul 26 2023 Valid 261300Z - 271200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHERN LOWER MICHIGAN AND NORTHERN PARTS OF INDIANA/OHIO... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK...AND OVER PARTS OF THE CENTRAL HIGH PLAINS... ....SUMMARY... Scattered severe thunderstorm gusts are possible today in parts of the southern Great Lakes, along with occasional large hail. Severe gusts also are possible over parts of the central High Plains this afternoon. ....Synopsis... The mid/upper-level pattern will remain broadly characterized by a strong anticyclone centered over NM, and a mean trough over the eastern CONUS. However, deamplification of the eastern trough, and the ridging north of the anticyclone, is making the wave train and flow field more zonal across the northern tier of states. The strongest embedded shortwave trough -- evident in moisture-channel imagery over portions of MN/IA -- is expected to move east-southeastward to Lake MI and western Lower MI around 00Z, then from southeastern ON to near a BUF-PIT-PKB line by 12Z tomorrow. Much weaker perturbations over parts of UT, WY and CO will round the broader-scale ridge slowly and cross parts of the central Rockies and adjoining High Plains through the period. The surface analysis at 11Z showed a warm frontal zone across eastern KY, central IN, and central IL, intercepted by an outflow boundary over the northeastern IA/northwestern IL area. A secondary warm front was drawn over central lake Michigan and central Lower MI. The boundaries should merge by afternoon as the southern warm front moves northeastward and becomes more diffuse, and the northern one is baroclinically reinforced by clouds/precip. ....Southern Great Lakes region... Scattered thunderstorms are expected through early afternoon across the southeastern WI/northeastern IL region, increasing in coverage and intensity as they impinge on a moistening and destabilizing air mass further east. This may evolve from very recently developed activity over northwestern IL. Initial discrete to clustered activity may evolve into an organized squall line with time. A corridor of damaging wind, with embedded severe gusts, appears possible in and near the "enhanced" area, along with the potential for a few line-embedded tornadoes, and occasional large hail. Near and south of the warm front, rich low-level moisture (with surface dewpoints commonly in the upper 60s to low 70s F) will persist, and advect into the outlook area ahead of the surface low and mid/upper-level shortwave trough. The same boundary layer will destabilize from diurnal heating and warm advection, leading to 2000-3000 J/kg MLCAPE. Mid/upper-level westerlies will increase as the trough aloft approaches, while having a large component normal to the convective-line orientation for wind-hazard enhancement. 35-40 kt effective-shear magnitudes and (especially over MI) 150-300 J/kg effective SRH also are evident in several forecast soundings, indicating potential for at least transient embedded supercells and/or LEWPs and bowing segments. Farther north, weaker buoyancy will be present in the warm-frontal zone and under areas of greater cloud cover left by morning activity, while lift and deep-layer flow/shear lessen with southward extent through IL/IN/OH. These factors constrain a corridor of greatest probable convective concentration and severe potential in and near the "enhanced" area from the southern Lake Michigan vicinity eastward across the Michiana area to southeastern MI and northwestern OH. Severe potential should diminish by late evening or early overnight hours near the astern and southern rims of the "marginal" area, as activity encounters substantially more low-level stability. ....Central/northern Plains... Isolated to scattered thunderstorms are expected to develop this afternoon from the central High Plains near and east of the Front Range foothills, near a surface trough to the central/eastern Dakotas and northern MN. Damaging gusts and large hail are at least locally possible. The greatest potential concentration of thunderstorms, and severe-gust threat, appears to be over parts of the central High Plains from central/southwestern NE into northeastern CO. In that area, hot surface temperatures and a deep/well-mixed boundary layer are expected, with essentially dry-adiabatic lapse rates forming a tall, wide "inverted-v" thermodynamic profile in forecast soundings. Still, enough moisture should be maintained through the deep mixing to support relatively abundant, high-based convection. Though deep shear will be modest, 30-40 kt of westerlies around the northern part of the anticyclone aloft will support easterly movement of convection across the region, with some cold-pool aggregation possible before activity decreases into more-stable air this evening. ...Edwards/Mosier.. 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) .