SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1135 PM CST Tue Nov 04 2025 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE PACIFIC NORTHWEST COASTLINE AND PORTIONS OF THE NORTHEAST... ...SUMMARY... Isolated severe thunderstorms are possible through the day along the western Oregon and far northern California coastal region. Strong, potentially damaging gusts may accompany the stronger showers or low-topped thunderstorms that can develop over parts of the Northeast. ...Synopsis... A mid-level trough will amplify while rapidly traversing the Northeast, with upper ridging prevailing over the central CONUS, and another mid-level trough impinging on the West Coast today. While surface high pressure and associated statically stable conditions should inhibit thunderstorms across much of the central U.S., at least isolated lightning flashes will be possible over the Northeast and Pacific Northwest coastline. In both regions, deep-layer ascent (and accompanying strong vertical wind shear), with cooler temperatures aloft, will overspread a marginally unstable boundary layer. As such, an isolated severe risk could accompany any of the stronger storms that can materialize over the Northeast and Northwest Pacific Coast. ...Northern California and Oregon Coastlines... As the mid-level trough overspreads the northern CA/Oregon coastlines during the morning hours, cooler temperatures aloft will foster steep mid-level lapse rates atop a maritime airmass, resulting in a couple hundred J/kg MLCAPE. Through the afternoon, rapidly strengthening winds with height will be in place, resulting in enlarged but mostly straight/elongated hodographs. Any thunderstorms that manage to develop will be capable of a couple strong to severe wind gusts. Some forecast soundings do show some low-level curvature closer to the coastline, with 150-250 m2/s2 effective SRH noted. As such, if a sustained, land-falling low-topped supercell can develop, a tornado cannot be ruled out. ...Portions of the Northeast... A surface low will deepen while traversing the Northeast, overspread by a 100+ kt 500 mb jet wind maximum and cooler temperatures aloft during the afternoon hours. Such conditions will support a dynamic and highly sheared environment over portions of the northern Appalachians into the Hudson Valley and southern New England. The rapid passage of a surface trough will limit moisture return during the day though. As such, any buoyancy that can develop will be scant at best. The current thinking is that the aforementioned cooling aloft, atop a marginally destabilized boundary layer, may support a couple hundred J/kg MLCAPE. Such buoyancy should be adequate for low-topped convective showers, but perhaps barely sufficient (if at all) for convective parcels to reach the -10C layer, which would foster the charge separation needed for lightning. Nonetheless, 40-60 kt west-southwesterly flow at 400-1000 m AGL will be present, from roughly central PA to southern New England. As such, any stronger showers (or perhaps short-lived low-topped thunderstorms) that can develop may encourage sufficient downward momentum transport for a few strong, potentially damaging wind gusts during the afternoon and evening hours. ..Squitieri/Wendt.. 11/05/2025
