SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Tue May 25 2021 Valid 251300Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN GREAT PLAINS AND THE UPPER GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms with large hail and damaging winds as the primary hazards are possible across parts of the Upper Great Lakes and the southern Great Plains, mainly from mid-afternoon through the evening. ...Central/Southern Great Plains... Large-scale mid-level height field will remain relatively nondescript with predominately weak to modest flow. Primary convective potential through this afternoon will likely be tied to an MCV across western North TX. Intensification of ongoing general thunderstorms is possible across mainly northeast TX, with perhaps additional development as convective outflow moves east. Isolated severe hail and wind are possible, mainly this afternoon, resulting in a broad expansion of the cat 1/MRGL risk. Farther west, late afternoon to evening thunderstorm development will probably occur with isolated to scattered coverage along the dryline from the TX Trans-Pecos north towards the composite front/outflow intersection in the Panhandles to south-central KS. Stabilization this morning across the Panhandles/TX South Plains in the wake of the western north TX MCS and the lack of any notable upstream shortwave impulses render lower-than-average confidence in convective evolution. This is supported by greater-than-average spread in available CAM guidance. Rather steep mid-level lapse should yield large buoyancy across a portion of west TX to the south of this morning's MCS, which appears to be well sampled by the 12Z Midland sounding. While deep-layer shear will be modest, a few organized multicell clusters with embedded supercell structures should prove favorable for isolated to potentially scattered large hail and severe wind through this evening. Given the degree of buoyancy and steepness of lapse rates across the Permian Basin to Concho Valley, significant severe appears possible in these regions. ...Upper Great Lakes... A shortwave trough near the south SK/MB border will shift east-southeast to the Upper Great Lakes through tonight. In response to this feature, a surface cyclone will translate across south MB into northwest ON this afternoon with a leading surface front/effective dryline arcing south across the MN Arrowhead to western IA by early to mid-afternoon. Robust boundary-layer heating will be noted across the Upper MS Valley ahead of the front amid 60-64 F dew points. This should yield moderate buoyancy with MLCAPE of 1000-1500 J/kg becoming common despite weaknesses in upper-level lapse rates. It appears adequate low-level convergence will be present for at least isolated thunderstorm development initiating across the MN Arrowhead and western WI by 19-20Z. Despite a nearly unidirectional southwesterly wind profile, strengthening flow in the mid-levels should support potential for upscale growth into organized clusters with embedded mid-level updraft rotation. Severe hail and damaging winds should be the primary hazards until convection weakens around dusk. ...West NY/Northwest PA... Strong heating is expected across western portions of NY/PA which will allow surface temperatures to warm towards the low 80s n the lee of Lake Erie. Although deep-layer flow will not be that strong, steep low-level lapse rates and MLCAPE around 500 J/kg could support a couple robust cells capable of producing locally damaging winds. ..Grams/Mosier.. 05/25/2021 Read more LIVE: spc.noaa.gov
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