MESOSCALE PRECIPITATION DISCUSSION 0093
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
757 AM EDT SAT MAR 26 2016
 
AREAS AFFECTED...FAR SOUTHEAST LA...EXTREME SOUTHERN MS...FAR
SOUTHERN AL...WESTERN FL PANHANDLE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 261155Z - 261730Z
 
SUMMARY...EXPANDING CLUSTERS OF CONVECTION THIS MORNING WILL
RESULT IN HEAVY RAINS. REPEATING/TRAINING CELLS MAY RESULT IN SOME
FLASH FLOOD/EXCESSIVE RAINFALL POTENTIAL THROUGH MIDDAY.

DISCUSSION...IR SATELLITE IMAGERY IS SHOWING RAPIDLY COOLING
CONVECTIVE TOPS ACROSS THE FAR NORTHERN GULF OF MEXICO OFFSHORE
THE CENTRAL GULF COAST. IN FACT...THE LATEST GOES-OTD ALGORITHM
SHOWS SEVERAL OVERSHOOTING TOPS WITHIN THE ACTIVITY SOUTH OF
MOBILE BAY...AND THE EXPERIMENTAL GLD-LIGHTNING DENSITY PRODUCT
SHOWS A DRAMATIC UPTICK IN STRIKE ACTIVITY WITHIN A SW/NE ORIENTED
FASHION OFFSHORE COINCIDING WITH THE COOLING CLOUD TOPS.

ALL OF THIS IS INDICATIVE OF LARGER SCALE ASCENT WHICH APPEARS TO
BE CONNECTED TO A SHORTWAVE IMPULSE TRAVERSING THE GULF COAST
STATES AS SUGGESTED BY A 0731Z RGB-MODIS PASS...AND PROXIMITY OF
AN ACTIVE SUBTROPICAL JET WITH A 110-120KT 250 MB JET STREAK
CROSSING SOUTHERN LA AND THE IMMEDIATE CENTRAL GULF COAST AS PER
THE 10Z RAP ANALYSIS. MEANWHILE...THE CONVECTION IS FOCUSING NEAR
A STATIONARY FRONT WHERE A NOTABLE INSTABILITY AXIS IS DEPICTED AS
PER THE LATEST RAP ANALYSIS. THE DEVELOPING CONVECTION IS WITHIN A
GRADIENT OF MUCAPE VALUES RANGING BETWEEN 1000 TO 2000 J/KG.

SOUTHWEST 850 MB FLOW OF 30 TO 40 KTS GENERALLY PARALLELING THE
BOUNDARY WILL CONTINUE TO POOL STRONGER INSTABILITY ALONG THE
FRONT THIS MORNING ALONG WITH PWATS OF 1.5 TO 1.75 INCHES. AN
0840Z AMSU PASS OVER THE NORTHERN GULF OF MEXICO ALREADY SHOWED
AREAL AVERAGE RAINFALL RATES UP TO 1 INCH/HR WITH EARLY
COLD-TOPPED CONVECTION...BUT WITH EVEN COLDER TOPS EXPANDING SINCE
THEN...EVEN HEAVIER RAINFALL RATES ARE LIKELY AS THIS ACTIVITY
LIFTS NORTH AND BEGINS OVERSPREADING THE CENTRAL GULF COAST AND
ESPECIALLY AREAS OF THE WESTERN FL PANHANDLE.

THE 00Z ARW AND 00Z NMMB BOTH APPEAR TO BE FOCUSING CONVECTION
THIS MORNING A BIT TOO FAR EAST...WITH THE 00Z NSSL-WRF DOING
BETTER WITH THE WESTERN AND NORTHERN EXTENT OF EXPANDING
CONVECTION. HOWEVER...RECENT RUNS OF THE HRRR DO NOT APPEAR TO BE
DOING TOO WELL AND ALSO ARE FOCUSED TOO FAR SOUTH AND EAST WITH
ITS CONVECTIVE AXIS.

BASED PRIMARILY ON SATELLITE AND RADAR TRENDS...EXPECT CONVECTION
TO EXPAND FURTHER IN COVERAGE THE NEXT FEW HOURS ALONG THE CENTRAL
GULF COAST...FROM FAR SOUTHEAST LA INTO FAR SOUTHERN AL AND THE
WESTERN FL PANHANDLE DUE TO THE APPROACHING SHORTWAVE AND JET
ENERGY.

RAINFALL RATES WILL BE AROUND 2 INCHES/HR...AND THERE WILL BE A
CONCERN FOR REPEATING/TRAINING CELLS GIVEN THE MEAN FLOW RELATIVE
TO THE SURFACE BOUNDARY. EXPECT RAINFALL AMOUNTS OF 3 TO 6 INCHES
LOCALLY THROUGH MIDDAY...AND THIS WILL CERTAINLY ENHANCE THE
THREAT FOR RUNOFF PROBLEMS AND SOME FLASH FLOODING...AND
ESPECIALLY FOR URBANIZED AREAS.

ORRISON

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

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

LAT...LON   31278687 31218568 30818480 30248450 29908451 
            29678489 29678516 29788569 30138666 29918768 
            29598839 29068926 28798996 28899004 28929028 
            29199038 29759006 30618886 31098788