1PM Day 3 Convective Outlook for Saturday, February 14. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY
SUMMARY
Isolated strong to severe storms are expected from portions of Oklahoma and Texas into the Lower Mississippi Valley Saturday afternoon into the overnight hours. Strong to locally damaging wind gusts are the most likely hazard.
Synopsis
A strong positively tilted, southern-stream shortwave trough is forecast to extend from the central High Plains southwestward into northern Mexico early Saturday. A pair of vorticity maxima will be embedded within this shortwave: the lead vorticity max moving through OK into the Lower MO Valley/Ozarks with the other farther southwest at the base of the trough over northern Mexico. This shortwave is forecast to progress quickly eastward across the southern Plains throughout the day, with the vorticity max (and associated jetlet) remaining within the base of the trough throughout the period. This evolution will result in strong forcing for ascent across TX and the Lower MS Valley as the shortwave moves eastward.
Mass response ahead of this system will result in significant low-level moisture advection across TX and the Lower MS Valley, with 60s dewpoints likely in place by late Saturday afternoon across much of east TX and adjacent far west LA. Mid 60s dewpoints are possible from the middle TX Coast through the Brazos Valley. Thunderstorms, including some severe storms, are expected as the progressing shortwave interacts with this moist and modestly buoyant airmass.
Southern Plains into the Lower MS Valley
Thunderstorms will likely be ongoing Saturday morning across northwest TX and western OK, supported by strong warm-air advection in the vicinity of a sharpening frontal zone. Buoyancy will be modest, but strong deep-layer vertical shear suggests a few organized updrafts capable of hail are possible. These storms will likely be elevated, but localized ascent attendant to the lead vorticity maximum mentioned in the synopsis (and associated potential for a more linear storm mode) could still result in a gust or two reaching the surface.
Additional thunderstorms will likely begin during the afternoon across the Edwards Plateau vicinity as the shortwave trough moves into the region, resulting in increased large-scale ascent as well as supporting an eastward push of the cold front. Thunderstorms are expected along this front as it surges eastward, with storms likely remaining close to the primary frontal zone. As such, a strong convective line appears probable. However, despite the airmass modification mentioned in synopsis, modest heating and poor lapse rates will support only modest destabilization over the warm sector. This should temper updraft strength and the overall severe potential. Damaging gusts within the frontal convective appears to be the primary risk, which could extend as far east as southwestern MS and southeast LA given the expectation that modest buoyancy will remain in these regions throughout the night.
Moderate to strong low-level shear supports a low-probability tornado risk from the middle TX Coast into southwest LA, but only if updrafts can be maintained ahead of the front. Confidence in this scenario is currently low given the warm temperatures aloft and resulting modest buoyancy within the warm sector.