Alert archive / Louisiana / Mesoscale Discussions in 2017
Mesoscale Discussion 80
The Storm Prediction Center issued this mesoscale discussion at Jan 20, 2017, 6:37 PM CST for 9 parishes in Louisiana; 7 counties in Texas. It was in force for 113 min.
The area
The outline as issued.
The facts
- Issued
- Jan 20, 2017, 6:37 PM CST (00:37 UTC)
- Expired
- Jan 20, 2017, 8:30 PM CST
- In force
- 113 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 60%
Counties Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Saint Landry Parish, LA, Chambers County, TX, Hardin County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Newton County, TX, Orange County, TX
The radar
The Lake Charles radar (KLCH), 23 km from the middle of the area, began a volume at 00:37 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
Lake Charles Mun, LA (KLCH), launched 00:00Z, 0.6 hours before the alert went out and 25 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.
438
ACUS11 KWNS 210038
SWOMCD
SPC MCD 210037
LAZ000-TXZ000-210230-
Mesoscale Discussion 0080
NWS Storm Prediction Center Norman OK
0637 PM CST Fri Jan 20 2017
Areas affected...southeast Texas through southwest Louisiana
Concerning...Severe potential...Watch possible
Valid 210037Z - 210230Z
Probability of Watch Issuance...60 percent
SUMMARY...Threat for mainly a few instances of damaging wind and
large hail will persist over southeast TX next couple hours,
spreading into southwest LA by mid evening. With time threat for a
few tornadoes is expected to increase, especially across southern
LA.
DISCUSSION...Early this evening a warm front separating rich Gulf
moisture from modified continental-polar air extends from southeast
LA westward to along the southeast TX coast. This boundary should
slowly develop inland, especially later tonight as the low-level jet
strengthens across LA. In the meantime, thunderstorms are expected
to continue developing initially over southeast TX, but spreading
into southwest LA by mid evening as a northeastward-ejecting
shortwave trough enhances ascent north of this boundary. As steeper
mid-level lapse rates advect eastward in the presence of low-level
theta-e advection, instability will increase and the thermodynamic
environment should become more supportive of robust updrafts. Strong
effective bulk shear will support some supercell and bowing
structures with initial threats being mainly large hail and damaging
wind. Weak low-level winds may initially limit short-term tornado
potential. However, the tornado threat is expected to increase by
mid-evening onward and especially later tonight over southern LA as
the strengthening low-level jet augments 0-1 km hodograph size.
..Dial/Edwards.. 01/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LCH...HGX...
LAT...LON 29759328 29709399 29489470 30089500 30839411 31009278
30659198 29879202 29759328SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jan 20, 7:32 PM CST | Tornado Watch | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 9 more | 6 hr |
| Jan 20, 10:04 PM CST | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Calcasieu, Cameron, Evangeline and 7 more | 116 min |
| Jan 20, 10:44 PM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Jefferson, Lafourche and 12 more | 61 min |
| Jan 20, 11:00 PM CST | Tornado Watch | SPC | Ascension, Assumption, Concordia, East Baton Rouge, East Feliciana, Iberville and 17 more | 8 hr |
| Jan 21, 1:41 AM CST | Mesoscale Discussion | SPC | Acadia, Avoyelles, Cameron, Evangeline, Iberia, Jefferson Davis and 5 more | 64 min |
| Jan 21, 2:55 AM CST | Mesoscale Discussion | SPC | Ascension, Assumption, East Baton Rouge, East Feliciana, Iberville, Jefferson and 16 more | 2 hr |
| Jan 21, 6:35 AM CST | Mesoscale Discussion | SPC | Jefferson, Lafourche, Orleans, Plaquemines, Saint Bernard, Saint Charles and 1 more | 55 min |
| Jan 21, 2:33 PM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Jackson and 8 more | 2 hr |
| Jan 21, 2:34 PM CST | Mesoscale Discussion | SPC | Allen, Ascension, Avoyelles, Catahoula, Concordia, East Baton Rouge and 16 more | 2 hr |
| Jan 21, 3:29 PM CST | Tornado Watch | SPC | Acadia, Ascension, Avoyelles, Catahoula, Concordia, East Baton Rouge and 22 more | 6 hr |
| Jan 21, 3:41 PM CST | Tornado Watch | SPC | Bienville, Bossier, Caddo, Caldwell, Claiborne, De Soto and 11 more | 7 hr |
| Jan 21, 5:32 PM CST | Mesoscale Discussion | SPC | Avoyelles, Bienville, Bossier, Caddo, Caldwell, Catahoula and 23 more | 118 min |
| Jan 20, 10:07 PM CST | Mesoscale Discussion | SPC | Brazoria, Chambers, Fort Bend, Hardin, Harris, Jasper and 10 more | 113 min |
Nearby
Mesoscale Discussions in Louisiana, 2017Mesoscale 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.