12AM Day 2 Convective Outlook for Friday, February 13. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF WESTERN TEXAS INTO FAR SOUTHWEST OKLAHOMA
SUMMARY
Isolated strong to severe thunderstorms could produce small to marginally severe hail Friday evening into the overnight hours across portions of western Texas into far southwest Oklahoma.
Texas and Oklahoma
A positive-tilt upper trough oriented from NV to just offshore from southern CA/northwest Mexico Friday morning, will shift east through the period, emerging over the central High Plains to southern Rockies by Saturday morning. As this occurs, increasing southwesterly mid/upper flow will overspread TX and OK. Lee low development over the southern High Plains will foster increasing south/southeasterly low-level flow across OK/TX, and modest boundary layer moisture will spread northwest across much of TX into OK. Mainly 50s to near 60 F dewpoints are expected across western/central TX into central OK. As cooling aloft ensues amid moistening vertical thermodynamic profiles, modest destabilization is expected across western TX and perhaps into southwest OK. MLCAPE values are generally forecast in the 500-1000 J/kg range, with weaker elevated instability expected with northeast extent into central OK.
Large-scale ascent will increase by late afternoon/early evening, and isolated thunderstorms are expected to develop by 00z. With temperatures warming into the 70s F across western TX, initial convection may briefly be surface-based. However, with nocturnal stabilization of the boundary-layer, convection will tend to become elevated with time. Supercell wind profiles, characterized by southeasterly low-level flow veering with height to southwesterly flow in the mid/upper levels, will support storm organization. Elongated/straight hodographs above 2-3 km, and steepening midlevel lapse rates suggest isolated large hail will be the primary risk with convection over western TX into far southwest OK, though a couple of strong gusts also could accompany storms that are surface-based.
Storm coverage will increase through the evening with northeast extent as a 30-40 kt southerly low-level jet increases across TX/OK. A strong storm or two could develop into central OK during the nighttime hours and produce small hail, but weaker midlevel lapse rates and MLCAPE less than 500 J/kg should temper the severe risk.