SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1251 AM CDT Mon Aug 19 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF EASTERN COLORADO... ...SUMMARY... Isolated severe thunderstorms with damaging winds will be possible across several areas of the Continental U.S. this afternoon evening. An organized large hail threat may materialize over eastern Colorado during the afternoon and evening. ...Synopsis... A mid-level trough will meander along the eastern seaboard as an upper ridge prevails across the Southwest into the Plains and another mid-level trough remains in place along the West Coast today. Given adequate moisture and instability, scattered to potentially numerous thunderstorms (some strong to locally severe) are expected along the periphery of both mid-level troughs and the upper ridge. ...North Carolina into the Northeast... At least scattered thunderstorms will develop amid weak vertical wind shear this afternoon ahead of a cold front. Pulse cellular and occasional multicells are the expected storm mode. Rich low-level moisture preceding the front will contribute to 1000-2000 J/kg MLCAPE, which may support a few strong, potentially damaging gusts with some of the stronger storms. ...North Florida... A couple of strong thunderstorms may develop along the trailing portion of a cold front by afternoon. Similar to the Northeast, rich low-level moisture will promote 2000-3000 J/kg MLCAPE, fostering wet downburst/strong wind gust potential with pulse single cells and multicells. ...Portions of the Lower Mississippi Valley... 2000-3000 J/kg MLCAPE may materialize across portions of southern AR into LA and far western MS during the afternoon on the backside of the East Coast mid-level trough. Tropospheric unidirectional northwesterly flow may contribute to enough deep-layer speed shear to support multicells capable of producing wet downbursts and subsequent strong/damaging wind gusts. ...Eastern Colorado... Moist upslope flow during peak surface heating will result in thunderstorm initiation off of the higher terrain. Surface dewpoints in the low 60s F beneath 7.5-8 C/km mid-level lapse rates will support over 2000 J/kg MLCAPE. Modest veering and strengthening of the vertical wind profile will contribute to 30-40 kts of effective bulk shear and modestly elongated hodographs. Multicells and occasional supercells are expected, with large hail the main threat, though a couple of severe gusts are also possible. ...Portions of the central and Northern Rockies... Broad 40+ kt southwesterly 500 mb flow will overspread portions of the central into the northern Rockies as an impulse embedded in the West Coast mid-level trough grazes the region. Steep mid-level lapse rates will overspread a deep boundary layer extending up to 500 mb. Scattered pulse-cellular and multicells should initiate over higher terrain areas during the afternoon and progress eastward through the afternoon and evening hours. Given the deep boundary layer and corresponding steep lapse rates, severe gusts are the primary threat, though a couple instances of large hail cannot be ruled out. ..Squitieri/Darrow.. 08/19/2024
