SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sat Jun 14 2025 Valid 141300Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL HIGH PLAINS... ...SUMMARY... Scattered severe thunderstorms capable of producing large hail and damaging wind gusts will be possible across parts of the northern and central High Plains this afternoon and evening. Isolated strong to severe thunderstorms may also occur today across parts of the southern Plains into the Ozarks, and over portions of the southern Mid-Atlantic. ...Northern/Central Plains into the Upper Midwest... Compared to yesterday, mid-level heights are generally forecast to remain neutral or even rise slightly today as upper ridging gradually builds over the southern/central Rockies. Even so, modestly enhanced southwesterly mid-level flow will persist over the northern Rockies and adjacent High Plains. A seasonably moist low-level airmass will remain over the northern/central High Plains today, with steep mid-level lapse rates also present. Daytime heating of this airmass should foster moderate to locally strong MLCAPE by mid to late afternoon. High-based thunderstorms should once again develop over the higher terrain of the northern/central Rockies by late afternoon, before spreading eastward over the High Plains this evening. Even though low-level winds are forecast to remain generally modest, veering and gradual strengthening of the flow with height through mid/upper levels should support around 35-50 kt of deep-layer shear (stronger across the northern High Plains). Supercells that become established will have mainly a large to very large (2+ inch diameter) hail threat, with any eventual clusters posing more of a severe wind risk with eastward extent through the evening. A separate area of strong to isolated severe thunderstorms is also apparent across parts of the Upper Midwest (IA vicinity) along/near a surface boundary. While deep-layer shear will likely remain weak, moderate instability may still support occasional hail and gusty downdraft winds with any of the more robust cores that can develop this afternoon and early evening. ...Southern Plains into the Ozarks... Ongoing convective clusters and cells this morning across southern KS and northern OK are being aided by weak southwesterly low-level warm/moist advection. With generally weak deep-layer shear present, the overall severe threat has remained generally isolated (reference Mesoscale Discussion 1283 for additional details on the short-term severe risk across south-central KS/northern OK). Still, steep lapse rates aloft (per area 12Z soundings) are contributing to substantial MUCAPE, which may support an isolated threat for hail and severe wind gusts through the morning hours as these thunderstorms spread generally east-southeastward along an instability gradient/surface front. It remains unclear how far east the ongoing cluster in southern KS may persist, with some guidance suggesting it may restrengthen into parts of western/central AR this afternoon. Have therefore expanded the Marginal Risk for severe/damaging winds eastward across this area. Considerable uncertainty remains regarding the potential for additional convection to develop along/near the trailing outflow from this morning activity across northern/central OK into south-central KS and vicinity. It appears likely that moderate to strong instability will be in place by late afternoon as diurnal heating of a very moist low-level airmass occurs along and south of the outflow boundary. But, large-scale ascent and deep-layer shear will remain weak for much of the day, with modest low-level warm advection forecast to gradually strengthen through the evening hours. Any thunderstorms which can develop in this rather favorable thermodynamic environment could pose an isolated threat for severe hail and damaging winds. But, confidence in a more focused corridor of severe potential remains too low to include greater severe hail/wind probabilities at this time. Isolated strong to severe thunderstorms may also develop this afternoon/evening across parts of the southern High Plains along/east of a surface lee trough/dryline, although forcing aloft will remain nebulous beneath upper ridging. ...Southern Mid-Atlantic... A weak mid/upper-level trough will move eastward across the Southeast and OH Valley today, eventually reaching the southern Mid-Atlantic by late tonight. A stalled surface boundary is located across parts of northern VA into MD and the Delmarva Peninsula this morning. This boundary is expected to move little through the day, and will likely serve as a focus for convection later this afternoon. Current expectations are for thunderstorms to initially develop around 20-22Z over the higher terrain of the Blue Ridge, and subsequently spread east-southeastward across the I-95 corridor in VA/DC/MD through the early evening. Various NAM/RAP forecast soundings suggest that even with poor lapse rates aloft, sufficient instability and modest deep-layer shear should be present along/south of the surface boundary to support some updraft organization. Occasional severe/damaging winds up to 60 mph and perhaps some marginally severe hail will be possible with the stronger cores through the evening, until they eventually weaken with the loss of daytime heating. ..Gleason/Kerr.. 06/14/2025