Mesoscale Discussion 1011
NWS Storm Prediction Center Norman OK
0209 PM CDT Tue Jun 13 2017
Areas affected...Portions of southwest TX
Concerning...Severe potential...Watch possible
Valid 131909Z - 132145Z
Probability of Watch Issuance...40 percent
SUMMARY...The area is being monitored for some severe thunderstorm
risk developing this afternoon and continuing into the evening.
Watch issuance will be possible.
DISCUSSION...Diurnally enhanced orographic circulations are
encouraging towering cumulus development over the Davis Mountains
and other southwest Texas mountains, on the east edges of nearly
dry-adiabatic lapse rates in the lowest 3 km above ground. This
initial convection should deepen, evolving into a couple of isolated
storms. Meanwhile, a dryline continues to sharpen from near the
southeast NM/southwest TX border southward to the international
border. This dryline will be a focused zone for additional,
possible, isolated thunderstorm development into the late afternoon
hours. However, stronger forcing for ascent, attendant to a midlevel
speed maximum advancing from the southern Rockies to the adjacent
Plains, will reside north of the area.
Nevertheless, sufficient deep shear peripheral to the speed
maximum -- e.g., effective shear of 25-35 kt -- may support a few
sustained/organized cells (possible supercells) with severe
hail/wind possible. Storm motion will be somewhat erratic, with a
general slow eastward/southeastward spread of convection east of the
dryline into the evening hours. Upward convective-scale
accelerations will be bolstered by 8.0-8.5 C/km lapse rates
overlying a relatively moist boundary layer east of the dryline,
characterized by lower/middle 60s dewpoints. This is supporting
upwards of 2500 J/kg of MLCAPE. Very isolated instances of
significant severe hail could occur. However, overall storm coverage
may be lacking, owing to the lack of stronger deep ascent.
Regardless, convective and environmental trends will continue to be
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 30650404 32270262 32870191 32780115 32250104 30160249