Mesoscale Discussion 481

Issued

Apr 28, 2016, 10:02 AM CDT (15:02 UTC)

Expired

Apr 28, 2016, 12:30 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

Counties Escambia County, FL, Orleans Parish, LA, Saint Bernard Parish, LA, Saint Tammany Parish, LA, Hancock County, MS, Harrison County, MS, Jackson County, MS

The Mobile radar (KMOB), 77 km from the middle of the area, began a volume at 15:03 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.

761 
ACUS11 KWNS 281503
SWOMCD
SPC MCD 281502 
FLZ000-ALZ000-MSZ000-LAZ000-281730-

MESOSCALE DISCUSSION 0481
NWS STORM PREDICTION CENTER NORMAN OK
1002 AM CDT THU APR 28 2016

AREAS AFFECTED...COASTAL AREAS AND BARRIER ISLANDS OF SOUTHEAST
LA...SOUTHEAST MS...SOUTHWEST AL AND PART OF THE FAR WESTERN FL
PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 281502Z - 281730Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...AN ISOLATED THREAT FOR WATERSPOUTS AND/OR A TORNADO AND
LOCALLY STRONG WIND GUSTS CANNOT BE RULED OUT IN VICINITY TO
OFFSHORE OF COASTAL AREAS OF SOUTHEAST LA...SOUTHEAST MS...SOUTHWEST
AL AND PERHAPS PARTS OF THE FAR WESTERN FL PANHANDLE.  LOCALIZED
SPATIAL THREAT CURRENTLY PRECLUDES THE ISSUANCE OF A TORNADO
WATCH...THOUGH CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED.

DISCUSSION...THE MERGING OF CONVECTIVE OUTFLOW BOUNDARIES WILL
CONTINUE TO BE PRODUCED BY NEW STORM DEVELOPMENT WITHIN THE
SOUTHWEST PERIPHERY OF A BACK-BUILDING MCS NEAR AND OFFSHORE THE
CENTRAL GULF COAST REGION OF SOUTHEAST MS AND SOUTHWEST AL.  THESE
STORM-SCALE BOUNDARY MERGERS WILL BE OF GREATEST CONCERN IN THE
SHORT-TERM AS THEY RESULT IN AN ENHANCED KINEMATIC /STRONGER SRH/
ENVIRONMENT FOR LOW-LEVEL ROTATION.  THIS HAS BEEN OBSERVED IN THE
MOB WSR-88D IMAGERY WITH A ROTATIONAL COUPLET LOCATED 20-25 SOUTH OF
KPQL.  MESOSCALE ANALYSIS INDICATED THE LEADING EXTENT OF THE
CONVECTIVE COLD POOL EXTENDED FROM EXTREME SOUTHWEST AL TO OFFSHORE
AND SOUTH OF THE AL/MS BARRIER ISLANDS...AND THEN WNWWD INTO
SOUTHEAST LA IN ST TAMMANY PARISH.

THE ENVIRONMENT IN THIS REGION IS QUITE MOIST AS SAMPLED BY THE LIX
12Z SOUNDING /PRECIPITABLE WATER NEAR 1.9 INCHES/...AND WITHIN A
CORRIDOR OF PW RANGING FROM 1.6-1.8+ INCHES FROM SOUTH OF LA INTO
SOUTHERN AL.  ALTHOUGH THE LOW-LEVEL WINDS ARE FORECAST TO BACK TO A
SOUTHERLY COMPONENT THIS AFTERNOON...A CONTINUED MOIST/UNSTABLE
INFLOW INTO THE SOUTHWEST PERIPHERY OF THIS MCS SUGGESTS IT SHOULD
PERSIST FOR A FEW MORE HOURS.  THIS WILL BE FURTHER SUPPORTED BY
THIS REGION LOCATED BENEATH DIFFLUENT FLOW REGIME ALOFT AND 30-40 KT
OF WLY 500-MB WINDS SPREADING ACROSS THIS AREA...MAINTAINING
EFFECTIVE BULK SHEAR FOR STORM ORGANIZATION.

..PETERS/CORFIDI.. 04/28/2016

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

ATTN...WFO...MOB...LIX...

LAT...LON   30519021 30548919 30578853 30618792 30598727 30368689
            29958710 29788764 29678838 29588889 29588927 29748956
            29958995 30219019 30519021

Mesoscale Discussions in Louisiana, 2016Mesoscale Discussions in Mississippi, 2016Mesoscale Discussions in Florida, 2016Every mesoscale discussion in 2016

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.