MESOSCALE PRECIPITATION DISCUSSION 0681
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
927 PM EST WED DEC 16 2015
 
AREAS AFFECTED...SOUTHERN MS...AL...NORTHERN GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 170230Z - 170800Z
 
SUMMARY...DEEP MOISTURE AND INSTABILITY FUNNELED ALONG A FRONTAL
BOUNDARY COULD RESULT IN CONVECTION WITH HEAVY TO LOCALLY
EXCESSIVE RAINFALL INTO THE EARLY MORNING HOURS. 

DISCUSSION...REGIONAL RADAR IS SHOWING AN UPTICK IN CONVECTIVE
ACTIVITY IN THE VICINITY OF A STATIONARY FRONT EXTENDING FROM EAST
LA ACROSS SOUTHERN MS/AL INTO SOUTHERN GA. SOUTH OF THE
FRONT...SURFACE DEW POINTS IN THE LOWER 70S ARE FEEDING MARGINAL
TO MODERATE INSTABILITY. THE 00Z KLIX SOUNDINGS SHOWED 1382 J/KG
OF SBCAPE...WHICH IS MORE ROBUST THAN HIGH RESOLUTION MODELS
(INCLUDING THE 21Z HRRR/RAP) WERE SHOWING FOR THAT TIME PERIOD.
EVEN NORTH OF THE FRONT...THE 00Z KJAN SOUNDING HAD 331 J/KG OF
SBCAPE... AGAIN HIGHER THAN HIGH RESOLUTION MODELS HAD DEPICTED. 

A LOW LEVEL 20 TO 25 KNOT SOUTHWEST FLOW IS TRANSPORTING 1.75 TO
2.00 INCH PRECIPITABLE WATER AIR (THE 00Z KLIX HAD A 1.84 INCH
PRECIPITABLE WATER VALUE) UP AND OVER THE FRONT INTO SOUTHERN MS
INTO CENTRAL AND NORTHERN AL. LIGHTNING STRIKES IN THIS AREA
INDICATED THAT THE INSTABILITY WAS BECOME ELEVATED WELL NORTH OF
THE SURFACE FRONT. LOCAL RADARS AND THE MRMS PRECIPITATION RATE
PRODUCT SHOWED HOURLY RATES BETWEEN 1.25 AND 1.50 INCHES OVER
SOUTHEAST MS AND SOUTHWEST AL... THOUGH SURFACE OBSERVATIONS
INDICATED THAT HOURLY RATES MAY BE CLOSER TO AN INCH.

A SURFACE WAVE DEVELOPING ON THE SURFACE LOW (IN RESPONSE TO A
SPEED MAXIMUM IN THE MID LEVELS) TRACKS NORTHEAST ACROSS SOUTHERN
MS/CENTRAL AL INTO NORTHERN GA. AHEAD OF THE LOW AND ITS SURFACE
FRONT... MODEL SOUNDINGS SHOWED MLCAPE VALUES GENERALLY AT OR
BELOW 500 J/KG...BUT BASED ON THE 00Z SOUNDINGS...THIS COULD BE
UNDERDONE. THE LOW LEVEL INFLOW INCREASES TO 35 TO 45 KNOTS AHEAD
OF THE FRONT... TRANSPORTING THE HIGH MOISTURE CONTENT AIR AHEAD
OF THE FRONT. 

WHILE THERE IS A SIGNAL FOR 2-3 INCHES OF RAINFALL WITH THE
CONVECTIVE AS IT TRACKS ALONG THE FRONT...THERE IS SOME SPREAD IN
WHERE THE HEAVIEST RAINFALL OCCURS. AT THIS POINT...IT WOULD
APPEAR AS THOUGH THE BEST THREAT FOR HEAVY TO LOCALLY EXCESSIVE
RAINFALL SHOULD EXTEND FROM SOUTHWEST AL INTO NORTHERN GA...MAINLY
IN THE 17/04Z TO 17/08Z TIME FRAME. AS THE CORFIDI VECTORS BECOME
BETTER ALIGNED WITH THE 850-300 MB FLOW...SOME TRAINING IS
POSSIBLE AHEAD OF THE FRONT...WHICH RAISES POTENTIAL FOR FLASH
FLOODING. 

HAYES

ATTN...WFO...BMX...FFC...HUN...JAN...LIX...MOB...

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

LAT...LON   34778518 34568442 32368586 30438816 30008900 
            30729008 32648926 34128694