Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 656

May 19, 20168 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at May 19, 2016, 7:53 PM CDT for 8 parishes in Louisiana. It was in force for 67 min.

The area

The outline as issued.

The facts

Issued: May 19, 2016, 7:53 PM CDT (00:53 UTC)
Expired: May 19, 2016, 9:00 PM CDT
In force: 67 min
Issued by: the Storm Prediction Center
Chance of a watch: 60%

Counties Assumption Parish, LA, Iberia Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Plaquemines Parish, LA, Saint Charles Parish, LA, St. Mary Parish, LA, Terrebonne Parish, LA

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 183May 19, 8:10 PM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 0.9 hours before the alert went out and 137 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2145 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: -6 m²/s²
0-3 km storm-relative helicity: 48 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

062 
ACUS11 KWNS 200053
SWOMCD
SPC MCD 200053 
LAZ000-200200-

MESOSCALE DISCUSSION 0656
NWS STORM PREDICTION CENTER NORMAN OK
0753 PM CDT THU MAY 19 2016

AREAS AFFECTED...SRN LA COAST

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 200053Z - 200200Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...VIGOROUS QLCS OVER THE NWRN GULF AND ASSOCIATED BOWING
SEGMENT WILL LIKELY MOVE ASHORE NEAR THE MOUTH OF THE ATCHAFALAYA
RIVER AND SUBSEQUENTLY MOVE EWD TOWARDS THE MOUTH OF THE MS RIVER
OVER THE NEXT SEVERAL HOURS.  AS A RESULT...THERE WILL BE AN UPGRADE
TO 15-PERCENT WIND PROBABILITIES AND CATEGORICAL SLIGHT RISK FOR THE
01Z OUTLOOK UPDATE.

DISCUSSION...A QLCS LOCATED FROM 25 W OF LFT SWD TO 120 MI SSW 7R4
IN THE OPEN GULF WATERS IS PROGRESSING ENEWD AROUND 35 KT.  THE
AIRMASS DOWNSTREAM OF THE CONVECTIVE SYSTEM IS CHARACTERIZED AS VERY
MOIST IN THE LOW LEVELS /LOW TO MID 70S DEWPOINTS/ ALONG AND S OF A
MARITIME/EFFECTIVE FRONT LOCATED NEAR THE I-10 CORRIDOR.  AN AN
UPPER TROUGH OVER OK WILL MOVE ENEWD TOWARDS THE OZARKS THIS
EVENING...AND FORCING FOR ASCENT AND STRENGTHENING DEEP-LAYER SHEAR
PROFILES WILL OVERSPREAD SERN LA AS A RESULT.  THE MAIN THREAT WITH
THE SQUALL LINE WILL BE ISOLD WIND DAMAGE VIA 50-65 MPH GUSTS AND
PERHAPS A MESOVORTEX OR TWO CAPABLE OF WIND DAMAGE.

..SMITH/EDWARDS.. 05/20/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LIX...LCH...

LAT...LON   29559211 29919183 30038939 29438891 28828915 28799186
            29559211

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 8:10 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Ascension, Assumption, East Baton Rouge, Iberia, Iberville and 18 more	6 hr
May 19, 10:22 PM CDT	Mesoscale Discussion	SPC	Ascension, Assumption, East Baton Rouge, Jefferson, Lafourche, Livingston and 10 more	83 min

Nearby

Mesoscale Discussions in Louisiana, 2016 Every 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.