Alert archive / Louisiana / Mesoscale Discussions in 2017
Mesoscale Discussion 643
The Storm Prediction Center issued this mesoscale discussion at May 3, 2017, 6:54 PM CDT for 9 parishes in Louisiana. It was in force for 96 min.
The area
The outline as issued.
The facts
- Issued
- May 3, 2017, 6:54 PM CDT (23:54 UTC)
- Expired
- May 3, 2017, 8:30 PM CDT
- In force
- 96 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Martin Parish, LA, West Baton Rouge Parish, LA
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 11.9 hours before the alert went out and 142 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
- 1959 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- 33 m²/s²
- 0-3 km storm-relative helicity
- 88 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted.
783
ACUS11 KWNS 032355
SWOMCD
SPC MCD 032354
LAZ000-040130-
Mesoscale Discussion 0643
NWS Storm Prediction Center Norman OK
0654 PM CDT Wed May 03 2017
Areas affected...South central Louisiana
Concerning...Severe potential...Watch unlikely
Valid 032354Z - 040130Z
Probability of Watch Issuance...20 percent
SUMMARY...Marginal wind/hail risk may persist for another couple of
hours on cold side of outflow, but a watch is not anticipated.
DISCUSSION...Bands of elevated thunderstorms are ongoing over south
central LA, in a zone of pronounced low-level warm advection atop
the cold pool generated by numerous thunderstorms through the day.
Surface observations show temperatures and dewpoints in the mid-low
60s, with the buoyancy feeding the storms rooted above the stable
surface layer. Strong storm-relative inflow from the southeast in
the low levels, along the northeast edge of the steeper midlevel
lapse rates, should help maintain the forward-propagating storms, as
well as a marginal risk for strong wind gusts and some hail.
However, the threat for damaging winds will be largely mitigated by
the stable near-surface layer within the cold pool. Thus, an
additional watch is not currently anticipated across southern LA.
..Thompson/Edwards.. 05/03/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LIX...LCH...
LAT...LON 30599182 30679122 30529064 30189043 29859049 29699076
29639112 29829151 30309197 30599182SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 7:04 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 13 more | 86 min |
| May 3, 7:32 AM CDT | Tornado Watch | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 24 more | 9 hr |
| May 3, 10:07 AM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Ascension, Assumption, Avoyelles, Beauregard and 21 more | 83 min |
| May 3, 12:34 PM CDT | Severe Thunderstorm Watch | SPC | Bossier, Caddo | 5 hr |
| May 3, 1:58 PM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Assumption, Beauregard, Calcasieu, Cameron and 11 more | 62 min |
| May 3, 3:48 PM CDT | Mesoscale Discussion | SPC | Acadia, Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis | 87 min |
| May 3, 3:59 PM CDT | Mesoscale Discussion | SPC | Bossier, Caddo | 91 min |
| May 3, 5:00 PM CDT | Severe Thunderstorm Watch | SPC | Acadia, Allen, Beauregard, Bienville, Calcasieu, Cameron and 10 more | 7 hr |
Nearby
Mesoscale Discussions in Louisiana, 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.