MESOSCALE PRECIPITATION DISCUSSION 0769
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
527 PM EST MON NOV 07 2016
 
AREAS AFFECTED...SE LA...SW MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 072226Z - 080056Z
 
SUMMARY...SMALL SCALE AND NEAR TERM THREAT FOR LOCAL FLASH
FLOODING IN AND AROUND NEW ORLEANS.

DISCUSSION...AT 22Z THUNDERSTORMS PRODUCING HEAVY RAIN IN
SOUTHEAST LOUISIANA WERE ALIGNED WITHIN BROADLY CONFLUENT LOW
LEVEL FLOW OUT AHEAD OF AN INVERTED SURFACE TROUGH. THE CONVERGENT
SIGNATURE WAS JUXTAPOSED WITH DIFLUENT UPPER LEVEL FLOW AHEAD OF A
90 KNOT 250 MB JET STREAK ALONG THE MIDDLE AND LOWER TEXAS COAST.
RADAR AND SATELLITE CHARACTER SHOWED THE CONVECTION WAS NOT
PARTICULARLY EXPANSIVE OR ROBUST IN ITS UPPER LEVEL
OUTFLOW...PERHAPS OWING TO THE INSTABILITY AXIS...UP TO 1000 J/KG
MUCAPE...BEING DISPLACED SOUTH OF THE BETTER FOCUSED DIFLUENCE
REGION WHICH WAS UP NEAR AND NORTH OF LAKE PONTCHARTRAIN PER RAP
ANALYSES. STILL...CONVECTION OF SHALLOW TO MODERATE DEPTH WORKING
ITS WAY NORTHWARD WILL INDUCE EFFICIENT RAINFALL PROCESSES WITH
RAP FORECAST SOUNDINGS SHOWING MODERATELY STEEP LAPSE RATES AND
FREEZING LEVELS ABOVE 13 KFT MSL.

DUAL-POL RAINFALL ESTIMATES OF CLOSE TO 3 INCHES OF RAIN IN PARTS
OF NEW ORLEANS ALONG THE SOUTH SHORE OF THE LAKE MATCHED WELL WITH
THE AVAILABLE MESONET AND CITIZEN GAUGES. NO INDIVIDUAL MODEL WAS
HANDLING THE CONVECTION VERY ACCURATELY...BUT HOURLY QPF FROM THE
SSEO MEAN WAS MERELY DISPLACED TO THE EAST WHILE ACTUALLY SHOWING
A SIMILAR ORIENTATION AND CHARACTER TO THE ONGOING ACTIVITY. IT
SUGGESTS CONTINUED LOOSELY ORGANIZED TRAINING OF CONVECTION FROM
SOUTH TO NORTH THROUGH AT LEAST 01Z...CAPABLE OF PUSHING EVENT
TOTALS ABOVE 4 INCHES IN ISOLATED SPOTS...WHICH WOULD APPROACH THE
HIGH FFG VALUES HERE. ISOLATED FLASH FLOODING IS POSSIBLE EARLY
THIS EVENING.

BURKE

ATTN...WFO...JAN...LIX...

ATTN...RFC...LMRFC...

LAT...LON   31139058 31138999 29348935 28988975 29869047