Alert archive / Texas / Mesoscale Discussions in 2017
Mesoscale Discussion 764
The Storm Prediction Center issued this mesoscale discussion at May 18, 2017, 4:55 PM CDT for 45 counties in Texas. It was in force for 95 min.
The area
The outline as issued.
The facts
- Issued
- May 18, 2017, 4:55 PM CDT (21:55 UTC)
- Expired
- May 18, 2017, 6:30 PM CDT
- In force
- 95 min
- Issued by
- the Storm Prediction Center
All 45 counties
Bosque County, TX, Brown County, TX, Callahan County, TX, Coke County, TX, Coleman County, TX, Collin County, TX, Comanche County, TX, Concho County, TX, Cooke County, TX, Coryell County, TX, Dallas County, TX, Denton County, TX, Eastland County, TX, Ellis County, TX, Erath County, TX, Fisher County, TX, Grayson County, TX, Hamilton County, TX, Haskell County, TX, Hill County, TX, Hood County, TX, Jack County, TX, Johnson County, TX, Jones County, TX, Lampasas County, TX, McCulloch County, TX, McLennan County, TX, Mills County, TX, Montague County, TX, Nolan County, TX, Palo Pinto County, TX, Parker County, TX, Rockwall County, TX, Runnels County, TX, San Saba County, TX, Shackelford County, TX, Somervell County, TX, Stephens County, TX, Stonewall County, TX, Tarrant County, TX, Taylor County, TX, Throckmorton County, TX, Tom Green County, TX, Wise County, TX, Young County, TX
The radar
The Dyess AFB radar (KDYX), 85 km from the middle of the area, began a volume at 21:58 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Fort Worth, TX (KFWD), launched 12:00Z, 9.9 hours before the alert went out and 111 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 2097 J/kg
- Mixed-layer CIN
- -180 J/kg
- Mixed-layer LCL
- 785 m above ground
- 0-6 km bulk shear
- 24 kt
- 0-1 km storm-relative helicity
- 93 m²/s²
- 0-3 km storm-relative helicity
- 71 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 2.3
The text
As transmitted.
963
ACUS11 KWNS 182156
SWOMCD
SPC MCD 182155
TXZ000-182330-
Mesoscale Discussion 0764
NWS Storm Prediction Center Norman OK
0455 PM CDT Thu May 18 2017
Areas affected...Portions of northern/central TX
Concerning...Tornado Watch 236...
Valid 182155Z - 182330Z
The severe weather threat for Tornado Watch 236 continues.
SUMMARY...Severe threat is increasing across Tornado Watch 236, with
all hazards possible through the evening.
DISCUSSION...Convection has recently initiated along and ahead of a
surface dryline across central TX per latest radar/satellite trends.
The atmosphere remains strongly unstable across the northern/central
TX, with MLCAPE in excess of 3000 J/kg due to strong diurnal heating
with surface temperatures in the upper 80s to lower 90s, dewpoints
in the mid 60s to lower 70s, and steep mid-level lapse rates. 45-50
kt of effective bulk shear will easily support supercells, with a
very large hail threat. Backed southeasterly low-level winds
veer/strengthen with height, and effective SRH is forecast to
increase to 200-250 m2/s2 over the next several hours as a southerly
low-level jet strengthens across the southern Plains this evening.
This increase in low-level shear suggests the tornado threat should
likewise increase through the evening. Thunderstorms may eventually
attempt to grow upscale into one or more bowing line segments later
this evening. If this occurs, then damaging winds would become the
primary threat with eastward extent across Tornado Watch 236.
..Gleason.. 05/18/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...SJT...LUB...
LAT...LON 31200088 33300025 33289843 33389790 33699774 33649648
33359630 32389646 31509680 31009857 30969962 31200088SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 18, 12:03 PM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Brown, Callahan, Clay, Coke and 37 more | 117 min |
| May 18, 12:59 PM CDT | Mesoscale Discussion | SPC | Childress, Collingsworth, Cottle, Hardeman, Wichita, Wilbarger | 2 hr |
| May 18, 1:18 PM CDT | Tornado Watch | SPC | Archer, Baylor, Childress, Clay, Collingsworth, Cottle and 12 more | 7 hr |
| May 18, 1:55 PM CDT | Tornado Watch | SPC | Bosque, Brown, Callahan, Coke, Coleman, Collin and 40 more | 10 hr |
| May 18, 3:02 PM CDT | Mesoscale Discussion | SPC | Baylor, Foard, Hardeman, Knox, Wichita, Wilbarger | 88 min |
Nearby
Mesoscale Discussions in Texas, 2017Every mesoscale discussion in 2017
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.