SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0138 PM CST Thu Dec 25 2025 Valid 252000Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF COASTAL CALIFORNIA AND THE CENTRAL VALLEY... ...SUMMARY... An isolated risk for severe gusts/localized wind damage and perhaps a brief tornado will be possible today into this evening along much of the California Coast and portions of the Central Valley. ...20z Update... The previous outlook reasoning remains on track, and no changes were made with this update. A few thunderstorms had developed over the Sacramento Valley since 18z, where partial clearing was noted and weak buoyancy (200-300 J/kg) was present. Offshore, an increase in lightning was noted as the next upstream vorticity maximum moves towards the CA Coast. Although buoyancy will remain weak, stronger low/mid-level flow will become re-established later this afternoon/evening and will support an isolated risk of strong/severe wind gusts with a few stronger/sustained convective elements, and low-level hodographs will be sufficiently curved to conditionally support a brief tornado. ..Bunting.. 12/25/2025 .PREV DISCUSSION... /ISSUED 1026 AM CST Thu Dec 25 2025/ ...California... Recent satellite imagery shows a mid/upper-level low over the eastern Pacific and a negative-tilt shortwave trough moving northward along the northern CA and OR Coast. An upstream mid-level jet and associated vorticity maximum will move through the base of the eastern Pacific upper low/trough and approach the San Francisco Bay and northern CA vicinity this evening. Strong to locally severe thunderstorms capable of producing mainly isolated severe/damaging winds will remain possible with convection today into this evening. Weak instability is forecast to persist across much of coastal CA into the Central Valley, with cool surface temperatures, saturated profiles, and modest lapse rates aloft (reference the 12Z OAK sounding) limiting the development of greater MUCAPE. Still, a favorable kinematic environment with enhanced west-southwesterly mid/upper-level flow will conditionally support occasional strong to severe convection, contingent on sufficiently deep/sustained updraft development. Low-level hodographs are forecast to remain enlarged enough to yield a low risk for a brief tornado across much of the Marginal Risk area. Consensus of latest model guidance indicates low/mid-level flow will weaken somewhat this afternoon before gradually re-intensifying this evening as the next embedded shortwave trough and associated mid-level jet overspread coastal northern/central CA. A mix of linear bands and cellular convective structures may continue to pose an intermittent risk for isolated damaging gusts and perhaps a brief tornado into this evening/tonight, before the severe threat gradually diminishes towards 12Z early Friday morning.
