SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1120 AM CDT Thu Jul 03 2025 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTH DAKOTA AND MUCH OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms capable of producing severe/damaging winds and large hail are forecast across parts of the Northeast and northern Plains today. ...Northeast... Recent satellite imagery shows a well-defined cyclone over northern QC and a shortwave trough embedded within the southern periphery of this cyclone progressing through the Lower Great Lakes. An attendant cold front is in place just ahead of this shortwave. Expectation is for this shortwave to continue quickly eastward into the Northeast, with the cold front progressing eastward/southeastward as well. The leading edge of the stronger large-scale forcing for ascent has already reached ME and NH, contributing to thunderstorm development where the preceding airmass has already destabilized. Continued destabilization is anticipated, likely resulting in a nearly continuous line of storms. In addition to moderate buoyancy, moderate vertical shear is in place as well. This combination of buoyancy and shear is expected to result in organized storms capable of large hail (more probable during the early-stage cellular mode) and damaging gusts (more probable later with later-stage linear modes). This ongoing development is well ahead of the primary cold front, so the potential exists for additional development across NY this afternoon, continuing into southern New England during the late afternoon and evening. Environmental conditions will be similar to those farther north and east, with large hail and damaging gusts possible with these storms as well. ...Northern Plains... Low-level moisture will continue to advect northwestward into the region today, helping to offset some of the anticipated mixing and keeping dewpoints in the upper 60s/70s later this afternoon/evening. This favorable low-level moisture beneath steep mid-level lapse rates will promote a very unstable airmass, with MLCAPE from 2000 to 3000 J/kg across ND this evening. Subtle ascent attendant to a modest vorticity maximum rounding the northwestern periphery of the central CONUS upper ridging will begin interacting with the westernmost edge of this moist and unstable airmass around 21Z-00Z. Initial cellular development is anticipated across northeast WY and far southeast MT, before expanding northeastward into more of ND over time. A risk for very large hail and perhaps a tornado would accompany initial supercells before storm outflow and mergers lead to upscale growth into an eastward-moving cluster during the evening. Once this upscale growth occurs, a quick northeastward progression is anticipated across ND with some severe wind gusts possible. An instance or two of gusts around 75 mph are possible. ...Southeastern ND/Northeast SD into the Upper Midwest... Recent regional radar imagery shows an MCV tracking east-northeastward over south-central ND. The airmass downstream from southeast ND/northeast SD into southern MN and northern IA is destabilizing amid strong heating and ample low-level moisture. As a result, there is a low-probability chance for thunderstorm redevelopment/reintensification early this afternoon in the vicinity of the MCV. If this occurs, isolated damaging gusts are possible. A more probable scenario is for this MCV to continue rounding the ridge and provide the impetus for thunderstorm development farther east across the Upper Midwest later this evening. Weak warm-air advection could augment ascent across the region as well. Moderate to strong buoyancy and moderate deep-layer vertical shear will be in place, supporting strong updrafts capable of large hail, particularly with initial development. Storms should continue throughout much of the night, with an isolated hail risk. ..Mosier/Karstens.. 07/03/2025