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SPC Jul 28, 2025 1730 UTC Day 2 Convective Outlook

3 weeks 2 days ago

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1224 PM CDT Mon Jul 28 2025 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN HIGH PLAINS INTO THE MID-MISSOURI VALLEY... ...SUMMARY... Severe thunderstorms are possible from southern Montana into the central High Plains as well as parts of the Mid-Missouri and Mid-Mississippi Valleys on Tuesday. ...Synopsis... A belt of enhanced northwesterly flow aloft will extend from portions of the Dakotas into the Great Lakes on Tuesday. A somewhat complex surface pattern is forecast. A low will likely be located over the southwest NE/northwest KS/northeast CO vicinity. A front will extend from the low northeast into central MN/northern WI Tuesday morning. Outflow from a severe MCS in the Day 1/Monday period may be located across portions of the Mid-MS Valley, but this is uncertain. A very moist and unstable airmass will reside to the east of the low and in the vicinity of these surface boundaries, with the corridor of greatest instability expected to extend from northeast CO eastward across NE and into IA/northern MO/northeast KS. Behind the surface front across portions of WY/MT into the Dakotas, boundary layer moisture will be maintained with dewpoints in the mid 50s to low 60s. This will support weak to moderate instability by afternoon. ...Northeast CO into NE and the Mid-MO Valley/central IA... This region will be displaced to the south from the belt of stronger mid/upper northwesterly flow. Nevertheless, strong instability and low-level convergence will support thunderstorm development during the afternoon near the surface low and northeastward along the surface front. Vertically veering wind profiles will support effective shear magnitudes in the 25-40 kt range, with initial supercells possible. With time, clustering is expected. One or more line segments or possibly a severe MCS could develop and move east across central/eastern NE into western/central IA and vicinity. Severe/damaging wind gusts will be the main hazard, but isolated hail may also occur, especially early in thunderstorm evolution. ...MT/WY into western SD/NE Panhandle... Scattered thunderstorms will develop during the afternoon in the moist post-frontal upslope regime. These areas will experience better shear, with stronger mid/upper westerly flow compared to points further southeast. Forecast soundings across eastern WY indicated effective shear magnitudes greater than 40 kt will be possible, with elongated/straight hodographs also noted. Steep midlevel lapse rates large instability through the cold layer aloft, in combination with favorable shear profiles, suggests cells producing isolated large hail will be possible, particularly from eastern WY into adjacent parts of MT/SD/NE. Further northwest into southern MT, instability will be lower and storm coverage more isolated. Still any storms that do develop will pose a risk for marginal hail. Where stronger heating occurs across the region, steepening low-level lapse rates could also support strong to severe wind gusts. ..ND... Isolated thunderstorms are expected to develop as a shortwave impulse migrates through west/northwesterly flow aloft. Buoyancy will be fairly weak this far north with only modest boundary-layer moisture persisting behind the surface front and generally warm temperatures aloft through about 600 mb. Nevertheless, strong mid/upper flow will support organized cells. Elongated/straight hodographs and effective shear greater than 40 kt suggests isolated marginal hail will be possible with any storms that develop. ..Leitman.. 07/28/2025 Read more