SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1137 PM CST Wed Dec 24 2025 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR MUCH OF THE CALIFORNIA COAST AND PORTIONS OF THE CENTRAL VALLEY... ...SUMMARY... Thunderstorms with potential to produce marginally severe wind gusts and perhaps a brief tornado will be possible on Thursday along much of the California Coast and portions of the Central Valley. ... Synopsis ... A highly amplified pattern will persist across the US as a deep trough over the eastern Pacific is maintained and a ridge builds over the central US. A series of embedded shortwave troughs within the eastern Pacific trough will impact the West Coast on Christmas and Christmas night. ... California ... The first of these shortwave troughs will be moving across the region at the start of the forecast period, bringing with it a band of strongly forced convection, likely located across portions of the central coast of California into the Central Valley. As the shortwave trough takes on an increasingly negative tilt, a 50-60 knot southerly low-level jet will be maintained allowing for sufficient low-level theta-e advection to support a modest 100-300 J/kg of surface-based CAPE. As the convective band interacts with this strong low-level kinematic field, gusty/damaging convective winds may be realized at the surface, particularly with the stronger convective elements. Forecast low-level hodographs ahead of this convective line feature sufficient low-level curvature to support a brief tornado should any convective element realize true surface-based buoyancy. As the morning progresses, the aforementioned shortwave trough will lift north then northwest within the broader cyclonic flow across the eastern Pacific whereas the band of convection slowly advances south and east. By midday, the low-level wind fields should weaken sufficiently in response to the departing shortwave trough to reduce the potential of damaging winds/tornadoes across far southern California. By mid-afternoon, another shortwave trough will approach the central and northern California coast. In response, the low-level wind fields will once again strengthen, albeit perhaps not to the extent as with the morning wave. Another band or bands of strongly forced convection are expected to develop across the eastern Pacific and approach coastal areas of central California after 00Z (4 PM PT). As was the case with the morning convection, the strongest convective elements may be capable of mixing down the stronger winds aloft resulting in the potential for isolated strong thunderstorm winds. ..Marsh/Squitieri.. 12/25/2025
