SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Oct 11 2025 Valid 111630Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE GREAT BASIN/SOUTHWEST AND COASTAL NORTH CAROLINA... ...SUMMARY... Isolated severe thunderstorms are possible this afternoon and evening across the eastern Great Basin and Southwest. A brief tornado and occasional strong to severe gusts could occur over the Outer Banks of North Carolina late tonight and early Sunday morning. ...Great Basin/Southwest... A prominent trough centered over the Pacific Northwest and northern California early today will shift eastward over the Great Basin and northern Intermountain region through tonight. This will be accompanied by considerable height falls/forcing for ascent and strengthening deep-layer southwesterly flow and an eastward-advancing cold front. Ahead of this system, a broad fetch of tropical moisture emanating from the eastern Pacific will continue to stream northward, with seasonally rich low/mid-level moisture expected across parts of the Southwest and southern Great Basin. As early day cloudiness quickly shifts eastward and abates, stronger daytime heating is expected, namely across parts of western/central Utah and central/southern Arizona. Still, mid-level lapse rates are expected to remain modest across these areas, and only weak instability is forecast where filtered diurnal heating can occur. Current expectations are for a gradual increase in coverage and intensity of thunderstorms this afternoon and evening across parts of the eastern Great Basin into the Southwest as large-scale ascent associated with the upper trough overspreads these areas. Occasional hail may occur with the stronger cores, as around 30-40 kt of deep-layer shear (maximized across Utah) supports organized updrafts. Otherwise, isolated strong to severe gusts should be the main threat with scattered to numerous thunderstorms that will spread east-northeastward through the afternoon and evening. ...Coastal North Carolina/Outer Banks... A surface low and warm front will approach late tonight/early Sunday, allowing for upper 60s to low 70s surface dewpoints to approach and potentially advect inland as east-northeasterly low-level flow strengthens late tonight. While lapse rates aloft will remain poor, some buoyancy increase is expected. While inland warm sector development remains uncertain, ample forecast low-level and deep-layer shear suggest some risk for a tornado and gusty winds with any supercell that can form in this environment across the Outer Banks/coastal North Carolina. ...East-central Montana... A couple of stronger storms with gusty winds could materialize this afternoon/early evening across the region, but it still seems that the potential for severe storms will be limited by meager moisture/buoyancy. ..Guyer/Moore.. 10/11/2025
