Alert archive / Texas / Mesoscale Discussions in 2017
Mesoscale Discussion 82
The Storm Prediction Center issued this mesoscale discussion at Jan 20, 2017, 10:07 PM CST for 16 counties in Texas. It was in force for 113 min.
The area
The outline as issued.
The facts
- Issued
- Jan 20, 2017, 10:07 PM CST (04:07 UTC)
- Expired
- Jan 21, 2017, 12:00 AM CST
- In force
- 113 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Brazoria County, TX, Chambers County, TX, Fort Bend County, TX, Hardin County, TX, Harris County, TX, Jasper County, TX, Liberty County, TX, Matagorda County, TX, Montgomery County, TX, Newton County, TX, Polk County, TX, San Jacinto County, TX, Tyler County, TX, Walker County, TX, Waller County, TX, Wharton County, TX
The radar
The Houston radar (KHGX), 57 km from the middle of the area, began a volume at 04:07 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
Lake Charles Mun, LA (KLCH), launched 00:00Z, 4.1 hours before the alert went out and 193 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
- 627 J/kg
- Mixed-layer CIN
- -37 J/kg
- Mixed-layer LCL
- 842 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 68 m²/s²
- 0-3 km storm-relative helicity
- 156 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 0.9
The text
As transmitted.
900
ACUS11 KWNS 210407
SWOMCD
SPC MCD 210407
TXZ000-210600-
Mesoscale Discussion 0082
NWS Storm Prediction Center Norman OK
1007 PM CST Fri Jan 20 2017
Areas affected...Portions of southeast Texas
Concerning...Severe potential...Watch unlikely
Valid 210407Z - 210600Z
Probability of Watch Issuance...20 percent
SUMMARY...Scattered thunderstorms will move east across the
discussion area this evening into the overnight hours. A couple of
these storms may reach severe limits, with the potential for large
hail. However, any instances of large hail should remain sparse
enough to preclude watch issuance.
DISCUSSION...Thunderstorms have re-developed across southeast Texas
late this evening, in response to increasing large-scale ascent (and
related mid-level cooling) along the leading edge of an impulse
transiting east towards the Gulf Coast. While drying aloft will
eventually shift the thunderstorm threat eastward into Louisiana,
these cells are developing along the leading edge of a plume of
steeper lapse rates aloft. With strong southwesterly mid/upper flow
positioned over the region, effective shear on the order of 40-45
kts is sufficient for organization of more robust updrafts rooted
above the cool/stable surface layer. As such, the strongest cells
may be capable of a few large hail reports over the next several
hours, before the activity moves east into Tornado Watch 9. Despite
this potential, however, increasing MUCIN (with the aforementioned
drying aloft) should keep the severe threat localized enough to
preclude watch issuance.
..Picca/Edwards.. 01/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LCH...HGX...
LAT...LON 29869619 30679580 30899519 31049404 31009375 30749362
29879431 29349477 28649587 28569630 29209634 29869619SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 20, 6:37 PM CST | Mesoscale Discussion | SPC | Chambers, Hardin, Jasper, Jefferson, Liberty, Newton and 1 more | 113 min |
| Jan 20, 7:32 PM CST | Tornado Watch | SPC | Jefferson, Orange | 6 hr |
| Jan 21, 2:33 PM CST | Mesoscale Discussion | SPC | Bowie, Cass, Harrison, Marion, Morris, Panola | 2 hr |
| Jan 21, 3:41 PM CST | Tornado Watch | SPC | Angelina, Bowie, Cass, Gregg, Harrison, Marion and 7 more | 7 hr |
| Jan 21, 5:32 PM CST | Mesoscale Discussion | SPC | Bowie, Cass | 118 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.