Valid 152000Z – 161200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE BIG
BEND/PECOS VALLEY OF WEST TEXAS…
Large hail, severe wind gusts, and a tornado or two are possible
across parts of the Big Bend and Pecos Valley regions of west Texas
this afternoon to about Midnight CDT.
Only minor adjustments have been made to previous forecast. Severe
storms are expected over southwest Texas this afternoon into the
evening with a threat for mainly large hail, damaging gusts and
possibly a tornado or two. See swomcd 183 for more information.
.PREV DISCUSSION… /ISSUED 1130 AM CDT Sun Mar 15 2020/
…Big Bend to Edwards Plateau of west TX…
60s surface dew points are prevalent across the Rio Grande Valley up
to the Big Bend and will be maintained into this evening as
low-level southeasterlies persist beneath an elevated mixed-layer as
sampled by the 12Z Del Rio sounding. A minor, low-amplitude impulse
and associated mid-level jet should progress from western Sonora
towards the western Trans-Pecos by evening. This feature should aid
in late afternoon thunderstorm development from the Davis Mountains
into northern Coahuila.
Amid 45-60 kt effective shear and steep mid-level lapse rates, at
least a couple supercells are expected across the southeast portion
of the Trans-Pecos, with a primary initial threat of large hail.
However, weakness in winds between 800-700 mb suggest that discrete
supercell mode may be of modest duration. Convective mode will
likely transition to a cluster and possibly grow into a short-lived
QLCS this evening, spreading across the Edwards Plateau. With little
movement to the quasi-stationary surface front, activity north of
the front will likely move over a progressively more-stable
near-surface layer. While activity south of the front will be
tempered by decreasing instability with negative low-level theta-e
advection from south/east TX tonight. This suggests the
spatiotemporal window for severe wind gusts will be limited.