SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1110 AM CST Tue Nov 11 2025 Valid 121200Z - 131200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across much of the U.S. Wednesday through Wednesday night. ...Discussion... As an increasingly prominent blocking high evolves near the southern Greenland Atlantic coast, it appears that broad mid/upper troughing will generally be maintained across the Atlantic Seaboard into Labrador Sea/Baffin Bay vicinity through this period, though large-scale ridging inland of the Pacific coast may slowly expand east of the Great Plains through Mississippi Valley. Upstream, particularly across the western into central mid-latitude Pacific, models indicate that flow will remain more progressive, with building ridging on the leading edge of this regime shifting across the central toward eastern Pacific. As this occurs, it appears that an initially digging downstream trough across the eastern Pacific will split while approaching the North American Pacific coast. There appears increasing consensus within/among the model output that forcing for ascent, associated with the most vigorous short wave perturbation within the southern portion of the splitting trough, will support significant lower/mid-tropospheric cyclogenesis late Wednesday through Wednesday night. The deepening, northeastward migrating surface cyclone center may approach the southern Oregon/northern California coast by 12Z Thursday, while the mid-level cold core remains farther offshore--and generally slower to approach the coast than suggested by prior guidance. ...Northern California... Latest high resolution, convection allowing ensemble output, and related guidance, suggests that the deepening surface cyclone might include an evolving warm sector corridor becoming sufficiently unstable to support a period of increasing pre-frontal thunderstorm development Wednesday evening, initially 100-200+ miles offshore of the northern California coast. Based on this same guidance, and forecast soundings from the NAM and Rapid Refresh, it remains unclear the extent to which thermodynamic profiles will remain conducive to convection capable of produce lightning, as the occluding cyclone/front approach coastal areas north of San Francisco Bay overnight through 12Z Thursday. Activity will be embedded within rather strong ambient wind fields, perhaps including 50-70 kt within the lowest kilometer or two above ground level. However, weak CAPE and stable near-surface lapse rates across and inland of coastal areas seem likely to limit the potential for convectively augmented surface gusts. ..Kerr.. 11/11/2025
