11AM Day 2 Convective Outlook for Saturday, February 28. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE SOUTHEAST FLORIDA COAST
SUMMARY
Isolated strong to severe thunderstorms are possible across parts of the Florida Peninsula Saturday afternoon and evening. Thunderstorms are also anticipated across portions of northern California into Oregon and Nevada as well as Oklahoma into the Ozark Plateau.
Synopsis
A broad northwest flow regime is expected to persist across the CONUS through Saturday. Thunderstorm chances will largely be focused in proximity to a pair of embedded upper-level shortwave troughs over the eastern Gulf and off the northern CA coast. At the surface, a cold front associated with an intensifying cyclone over the Canadian Prairies will push south and east across the Plains and Midwest over the next 36-48 hours, eventually stalling across OK and the Ozark Plateau late Saturday into early Sunday morning. Weak ascent along this frontal zone will promote isolated thunderstorm chances.
Florida
Mid-morning surface observations depict a cold front drifting southeast into the northern Gulf and Southeast. This feature is expected to gradually migrate southward over the next 48 hours as surface high pressure builds across the Southeast. However, gradual frontolysis is expected, which will help maintain the moist air mass building across southern to central FL, where dewpoints have increased to the upper 60s and low 70s. An upper wave over the northern Gulf will overspread the FL Peninsula around peak heating Saturday. Modest broad-scale ascent within a moist, weakly capped, and fairly unstable (1000-1500 J/kg MLCAPE) air mass should promote isolated to scattered thunderstorms. 30-40 knot mid-level flow attendant to the upper wave will allow for adequate hodograph elongation for organized thunderstorms capable of severe hail and damaging winds. Diminishing low-level convergence along the frontal zone casts uncertainty on overall storm coverage, but most 12z CAMs and global guidance show a consistent QPF signal along the southeastern FL coast where localized sea-breeze convergence/ascent may increase thunderstorm chances.
.Northern California and adjacent states
A low-amplitude upper disturbance is noted in morning water-vapor imagery well off the northern CA coast approaching the crest of the longwave ridge. This feature will begin moving inland across northern CA by late Saturday morning, reaching the western Great Basin by evening/overnight. An influx of moisture from the Pacific will support deep moistening of profiles across the region. This, combined with steepening lapse rates/cooling temperatures aloft, will support favorable buoyancy for isolated to scattered thunderstorms. MUCAPE is forecast to generally be near/below 250 J/kg, but pockets of higher buoyancy (closer to 500 J/kg) appear possible based on recent CAMs, which may support storms capable of small hail and gusty winds.
.Oklahoma into the Ozark Plateau
Surface high pressure currently positioned over the Texarkana region will migrate east/southeast over the next 24 hours in the wake of the ongoing frontal passage into the northern Gulf/Southeast. Southerly flow on the western periphery of this high, coupled with modest lee troughing along the High Plains, will promote modest moisture return through Saturday evening. Isolated showers and weak thunderstorms appear possible Saturday afternoon within the low-level warm advection regime with a slight uptick in convection anticipated late evening/overnight as the approaching cold front settles into the region. Model consensus suggests buoyancy profiles will be too limited to support intense convection.