Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 129
The Storm Prediction Center issued this mesoscale discussion at Feb 25, 2021, 6:50 PM CST for Union County, Arkansas; 6 parishes in Louisiana; Gregg County, Harrison County, Marion County, Texas. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Feb 25, 2021, 6:50 PM CST (00:50 UTC)
- Expired
- Feb 25, 2021, 8:45 PM CST
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
Counties Union County, AR, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, Lincoln Parish, LA, Union Parish, LA, Webster Parish, LA, Gregg County, TX, Harrison County, TX, Marion County, TX
The radar
The Shreveport radar (KSHV), 37 km from the middle of the area, began a volume at 00:53 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
Shreveport, LA (KSHV), launched 00:00Z, 0.8 hours before the alert went out and 31 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1097 m above ground
- 0-6 km bulk shear
- 86 kt
- 0-1 km storm-relative helicity
- 288 m²/s²
- 0-3 km storm-relative helicity
- 522 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.8
The text
As transmitted.
972 ACUS11 KWNS 260051 SWOMCD SPC MCD 260050 LAZ000-ARZ000-TXZ000-260245- Mesoscale Discussion 0129 NWS Storm Prediction Center Norman OK 0650 PM CST Thu Feb 25 2021 Areas affected...Northeast TX...Southern AR...Northern LA Concerning...Severe potential...Watch unlikely Valid 260050Z - 260245Z Probability of Watch Issuance...5 percent SUMMARY...Marginally severe hail may accompany thunderstorms from northeast Texas into southern Arkansas and northern Louisiana this evening. Severe thunderstorm watch does not appear warranted at this time. DISCUSSION...Early-evening satellite imagery depicts a fairly well-defined short-wave trough over NM, moving east toward the southern High Plains. In response to this feature, LLJ is beginning to increase across east TX. Over the last few hours, agitated convection has gradually increased in depth/intensity with several robust updrafts now evident from Gregg County TX to Caddo Parish LA. This activity is likely quite elevated in nature, but strongly sheared. 00z sounding from SHV exhibits roughly 400 J/kg MUCAPE if lifting a parcel near 760mb. Given the observed shear, there is some concern that organized, potentially rotating updrafts, will continue along a corridor from northeast TX into southern AR/northern LA where low-level warm advection is maximized. Even so, hail may struggle to reach severe levels, and unless trends change appreciably, severe thunderstorm watch does not appear warranted. ..Darrow/Grams.. 02/26/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...JAN...LZK...SHV... LAT...LON 32939461 33419224 32639178 32289370 32369518 32939461
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 25, 11:25 PM CST | Mesoscale Discussion | SPC | Columbia, Lafayette, Miller, Union | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Arkansas, 2021Every mesoscale discussion in 2021
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.