Valid 291300Z – 301200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY THROUGH
TONIGHT ACROSS CENTRAL TX…AND OVERNIGHT IN SOUTHEAST LA…
…SUMMARY…
Thunderstorms with marginally severe hail, isolated damaging gusts
and possibly a brief tornado are expected today into tonight across
the middle Texas coast and central Texas. A brief tornado cannot be
ruled out overnight across southeast Louisiana.
…Synopsis…
Large-scale cyclonic flow aloft will dominate the western and
central CONUS through tonight, as an embedded shortwave trough digs
southeastward over the Great Basin to the Four Corners, and a ridge
persists near the Bahamas. At the surface, a slow-moving front will
drift northward to the north central Gulf coast by tonight as a weak
subtropical midlevel low moves northward toward LA. The western
extent of this boundary will remain quasi-stationary, with the
middle/lower TX coast and deep South TX remaining in the warm
sector. A maritime tropical air mass will persist across the FL
peninsula, south of the slow-moving front.
…Central TX through tonight…
Increasing clouds/rain through the day will reinforce the sharp
front and cool air mass across the southern Plains, which will limit
any potential for lee cyclogenesis. Modest low-level southwesterly
flow atop the cool air will support moistening and a gradual
increase in the threat for elevated thunderstorms from TX to OK and
AR through tonight. Midlevel lapse rates near 7 C/km, MUCAPE near
1500 J/kg, and effective bulk shear near 40 kt could favor
marginally severe hail in the strongest elevated storms today into
tonight across central TX. Storms rooted closer to the surface are
expected along the boundary in the vicinity of the middle TX coast
today, where a low-end supercell environment could support isolated
damaging gusts and perhaps a brief tornado.
…Southeast LA overnight…
There will be some increase in low-level shear this evening into
tonight across southeast LA in advance of the weak subtropical low.
Here, a few weakly rotating storms, and perhaps a brief tornado, may
occur tonight as the warm sector (70 F dewpoints) and weak
surface-based buoyancy spread inland.
..Thompson/Smith.. 10/29/2019
$$