Alert archive / Louisiana / Mesoscale Discussions in 2016
Mesoscale Discussion 655
The Storm Prediction Center issued this mesoscale discussion at May 19, 2016, 5:42 PM CDT for 10 parishes in Louisiana; 4 counties in Mississippi. It was in force for 93 min.
The area
The outline as issued.
The facts
- Issued
- May 19, 2016, 5:42 PM CDT (22:42 UTC)
- Expired
- May 19, 2016, 7:15 PM CDT
- In force
- 93 min
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
Counties Ascension Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Iberville Parish, LA, Livingston Parish, LA, Pointe Coupee Parish, LA, Saint Helena Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, Lamar County, MS, Marion County, MS, Pearl River County, MS, Walthall County, MS
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Slidell Radar S, LA (KSIL), launched 12:00Z, 10.7 hours before the alert went out and 89 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
- 269 J/kg
- Mixed-layer CIN
- -262 J/kg
- Mixed-layer LCL
- 634 m above ground
- 0-6 km bulk shear
- 29 kt
- 0-1 km storm-relative helicity
- 99 m²/s²
- 0-3 km storm-relative helicity
- 137 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.6
The text
As transmitted.
243
ACUS11 KWNS 192242
SWOMCD
SPC MCD 192242
MSZ000-LAZ000-200015-
MESOSCALE DISCUSSION 0655
NWS STORM PREDICTION CENTER NORMAN OK
0542 PM CDT THU MAY 19 2016
AREAS AFFECTED...PARTS OF SERN LA AND SRN MS
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 192242Z - 200015Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...ISOLATED THUNDERSTORMS WITH THE POTENTIAL FOR HAIL AND
STRONG WIND GUSTS WILL AFFECT PARTS OF SERN LA AND SRN MS FOR THE
NEXT COUPLE HRS. THESE THREATS ARE EXPECTED TO REMAIN TOO MARGINAL
AND SHORT-DURATION IN NATURE TO PRECLUDE WW ISSUANCE.
DISCUSSION...VISIBLE SATELLITE TRENDS SHOW DEVELOPING THUNDERSTORMS
ALONG A WEAKLY CONVERGENT AND NEARLY STATIONARY BOUNDARY NEAR I-10
ACROSS PARTS OF SERN LA. THIS IS OCCURRING DOWNSHEAR FROM THE NRN
FLANK OF A MCS APPROACHING SWRN LA...AND SUFFICIENT
HEATING/DESTABILIZATION HAS OCCURRED WITHIN A MOIST BOUNDARY LAYER
TO YIELD MLCAPE VALUES APPROACHING 1500 J/KG. MORE RECENT RADAR
TRENDS SUGGEST THE POTENTIAL FOR HAIL APPROACHING SVR LIMITS WILL BE
POSSIBLE WITH THESE STORMS...SUPPORTED BY THE PRESENCE OF 7-7.5 C/KM
LAPSE RATES NOTED IN MORNING REGIONAL SOUNDINGS. LOW-LEVEL FLOW IS
WEAK /PER LIX AND LCH VWP/...BUT STRONGER FLOW ABOVE 2 KM AGL IS
YIELDING SUFFICIENT EFFECTIVE SHEAR MAGNITUDES /30-40 KT/ TO
MAINTAIN ORGANIZED STORMS. A FEW STRONG WIND GUSTS MAY ALSO DEVELOP
GIVEN THE DIURNAL STEEPENING OF LOW-LEVEL LAPSE RATES THAT HAS
OCCURRED...BUT THIS THREAT SHOULD REMAIN LOCALIZED. BOTH THE
HAIL/WIND THREAT SHOULD PERSIST FOR THE NEXT 1-2 HRS...BEFORE
GRADUALLY DIMINISHING WITH THE LOSS OF DIURNAL HEATING.
..ROGERS/EDWARDS.. 05/19/2016
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...JAN...LIX...LCH...
LAT...LON 31098933 30628960 30309022 30159084 30089133 30239168
30629182 30839150 31149035 31398925 31098933Nearby
Mesoscale Discussions in Louisiana, 2016Mesoscale Discussions in Mississippi, 2016Every mesoscale discussion in 2016
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.