Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0632 AM CST Sat Dec 20 2025 Valid 201300Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected, but a few lightning flashes may occur today near coastal Washington. ...Discussion... Progressive/low-amplitude flow aloft will prevail over the CONUS to the south of an amplifying shortwave trough over the Great Lakes/Ontario. Surface high pressure will expand eastward across the Plains and Midwest. Some inland moistening will occur across east Texas toward the Lower Mississippi Valley via the western Gulf, but weak forcing/capping will hinder appreciable convective development. In the Pacific Northwest, a marginally supportive thermodynamic environment may allow for a few lightning flashes near the Washington coast today and tonight. ..Guyer/Marsh.. 12/20/2025Read more