Alert archive / Texas / Mesoscale Discussions in 2017
Mesoscale Discussion 802
The Storm Prediction Center issued this mesoscale discussion at May 20, 2017, 3:46 PM CDT for 25 counties in Texas. It was in force for 59 min.
The area
The outline as issued.
The facts
- Issued
- May 20, 2017, 3:46 PM CDT (20:46 UTC)
- Expired
- May 20, 2017, 4:45 PM CDT
- In force
- 59 min
- Issued by
- the Storm Prediction Center
All 25 counties
Atascosa County, TX, Bee County, TX, Bexar County, TX, DeWitt County, TX, Dimmit County, TX, Duval County, TX, Frio County, TX, Goliad County, TX, Gonzales County, TX, Guadalupe County, TX, Jim Wells County, TX, Karnes County, TX, Kinney County, TX, La Salle County, TX, Lavaca County, TX, Live Oak County, TX, Maverick County, TX, McMullen County, TX, Medina County, TX, San Patricio County, TX, Uvalde County, TX, Victoria County, TX, Webb County, TX, Wilson County, TX, Zavala County, TX
The radar
The Laughlin AFB radar (KDFX), 155 km from the middle of the area, began a volume at 20:48 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 nearest sounding before it
Corpus Christi, TX (KCRP), launched 12:00Z, 8.8 hours before the alert went out and 186 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
- 2452 J/kg
- Mixed-layer CIN
- -31 J/kg
- Mixed-layer LCL
- 634 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 88 m²/s²
- 0-3 km storm-relative helicity
- 153 m²/s²
- Significant tornado parameter
- 1.7
- Supercell composite
- 8.8
The text
As transmitted.
237
ACUS11 KWNS 202047
SWOMCD
SPC MCD 202046
TXZ000-202145-
Mesoscale Discussion 0802
NWS Storm Prediction Center Norman OK
0346 PM CDT Sat May 20 2017
Areas affected...Portions of south-central TX
Concerning...Severe Thunderstorm Watch 253...
Valid 202046Z - 202145Z
The severe weather threat for Severe Thunderstorm Watch 253
continues.
SUMMARY...Several supercells persist mainly across western portions
of Severe Thunderstorm Watch 253, with an isolated large hail and
damaging wind threat continuing. A southward expansion in area
and/or an extension in time may be needed for some portions of the
watch prior to its scheduled 22Z expiration.
DISCUSSION...A cold front has made little southward progress across
south-central TX this afternoon, with a very moist and unstable
airmass present to the south of the front. The thermodynamic and
kinematic environment remains favorable for sustained severe
convection, and recent radar imagery shows several supercells across
Frio, La Salle, and Dimmit counties in TX. Isolated large hail and
damaging winds will be possible with this ongoing convection as it
moves southeastward with time. Additional showers have formed across
parts of deep south TX, and if this activity can strengthen, it may
also pose some severe risk given the favorable environment. Latest
short-term guidance continues to suggest ongoing supercells should
develop southeastward off the front over the next several hours into
more of south-central/deep south TX. Depending on radar trends
through 22Z, a southward expansion in area and/or an extension in
time may be needed for some portions of the Severe Thunderstorm
Watch.
..Gleason.. 05/20/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...EWX...
LAT...LON 28290037 29380087 29619982 29589689 28649698 27629760
27409818 27439954 27579962 27819994 28290037SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 19, 7:15 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coke, Coleman, Concho, Fisher and 11 more | 60 min |
| May 19, 7:44 PM CDT | Tornado Watch | SPC | Brown, Callahan, Coke, Coleman, Concho, Fisher and 15 more | 7 hr |
| May 19, 11:05 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coke, Coleman, Comanche, Concho and 14 more | 115 min |
| May 20, 7:41 AM CDT | Mesoscale Discussion | SPC | Aransas, Atascosa, Bandera, Bee, Bexar, Caldwell and 21 more | 94 min |
| May 20, 10:15 AM CDT | Severe Thunderstorm Watch | SPC | Atascosa, Bee, Bexar, DeWitt, Dimmit, Duval and 18 more | 11 hr |
| May 20, 12:56 PM CDT | Mesoscale Discussion | SPC | Atascosa, Bee, Bexar, DeWitt, Dimmit, Frio and 13 more | 94 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.