SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0212 AM CDT Sun Sep 28 2025 Valid 301200Z - 011200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. Tuesday through Tuesday night. ...Discussion... Downstream of amplified mid-level ridging slowly shifting eastward into the Hudson Bay/Ontario/upper Great Lakes vicinity, models indicate that a significant short wave trough will dig across the St. Lawrence Valley through Canadian Maritimes. As this occurs, it appears that expansive cold surface ridging will begin to build across much of the eastern Canadian provinces through Great Lakes, Northeast and Mid Atlantic by the end of the period. Upstream, a deep mid-level trough and embedded lower/mid-tropospheric cyclone are forecast to continue slowly approaching southern British Columbia and Pacific Northwest coastal areas, preceded by a couple of weak short wave perturbations accompanied by modest deepening surface troughing across the Canadian Prairies into the lee of the northern U.S. Rockies. Within a belt of weaker flow, to the south of a blocking mid-level high lingering over the Midwest/middle Mississippi Valley, weak mid-level troughing is forecast to dig offshore of the Texas Gulf coast into the western Gulf Basin. As downstream troughing lingers across and offshore of the south Atlantic Seaboard, guidance generally indicates that an initially stalling or slow moving developing hurricane offshore will slowly accelerate eastward, either parallel to or farther away from the coast. As this regime evolves, it is possible that residual low-level moisture and/or cooling aloft may contribute to sufficient destabilization for areas of scattered thunderstorm development, from near Pacific Northwest coastal areas into the northern Great Plains. However, it appears this will be mostly modest to weak in intensity, with generally negligible risk for severe weather. ..Kerr.. 09/28/2025
