SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0127 PM CST Tue Dec 16 2025 Valid 162000Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE PACIFIC NORTHWEST... ...SUMMARY... Sporadic severe wind gusts may accompany low-topped convection across parts of the Pacific Northwest tonight into early Wednesday morning. ...20z Update... No changes are needed to the D1 Convective Outlook. See previous discussion for more information. ..Thornton.. 12/16/2025 .PREV DISCUSSION... /ISSUED 1020 AM CST Tue Dec 16 2025/ ...Pacific Northwest... A strong mid-level shortwave trough over the eastern Pacific will amplify today and reach the coastal Pacific Northwest late tonight. This trough will be accompanied by an enhanced deep-layer wind field, with 90-100+ kt winds at 500 mb and around 50-80 kt flow in the lowest 1-3 km AGL. Low-level moisture should also gradually increase tonight ahead of an eastward-advancing cold front. Low-topped convection may accompany the front, initially approaching the WA Coast by late evening, and then more interior areas overnight/early Wednesday. Surface-based buoyancy will remain quite meager due to poor lapse rates aloft and the time of night. Still, rather strong low-level gradient winds will shift from the southwest to west-northwest as the front passes. Sporadic lightning flashes and occasional strong to severe-caliber wind gusts may accompany the passage of this low-topped convective line, with the most intense low-level winds/convective influences expected to peak during the overnight and early morning hours Wednesday. However, it remains quite uncertain if these convectively enhanced winds will be substantially stronger than the background gradient wind field. Therefore, the Marginal Risk has been maintained with no changes.
