SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1145 PM CST Tue Dec 16 2025 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE NORTHWEST... ...SUMMARY... Sporadic severe gusts may accompany low-topped convection across parts of the Northwest this morning into midday. ...Northwest... A vigorous shortwave trough will move quickly east along the Canadian border from WA to the northern Great Plains by evening. Intense tropospheric flow will accompany this wave, yielding widespread high winds across much of the Northwest to the northern Great Plains. Deep lee surface cyclone over southern AB should reach the Red River Valley of the North. Attendant Pacific cold front will sweep east with a tight pressure gradient in its wake. Low-topped convection may be ongoing at 12Z along the Columbia Basin portion of the front. Most guidance also suggests an increase in low-topped convection should occur towards late morning across parts of the Snake River Plain as the front pushes east. Surface-based instability will remain scant in both regimes with morning temperatures in the 40s to low 50s. Despite the cool temperatures, this may be sufficient for sporadic lightning flashes amid strong large-scale ascent. With very strong surface winds accompanying the front, both regimes could be coincident with severe wind gusts. The bulk of sustained severe wind speeds should become primarily confined along/east of the Rockies in MT to the CO Front Range this afternoon per HREF/REFS guidance. However, potential for severe convective gusts appears too conditional with negligible surface-based buoyancy anticipated. ..Grams/Wendt.. 12/17/2025
