MESOSCALE PRECIPITATION DISCUSSION 0634
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
729 PM EDT SAT OCT 31 2015
 
AREAS AFFECTED...FAR SOUTHEAST MS ...SOUTHERN AL...WESTERN FL
PANHANDLE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 312328Z - 010300Z
 
SUMMARY...LINE OF CONVECTION MOVING EAST INTO SOUTHWEST ALABAMA
WILL PRESENT A MARGINAL FLASH FLOOD RISK INTO THE EVENING.

DISCUSSION...RADAR CONTINUES TO SHOW A LINE OF THUNDERSTORMS
MOVING EAST AT 30-40 MPH ACROSS SOUTHEAST MS INTO SOUTHWEST AL. 40
KTS OF WIND AT 850 MB PER THE MOBILE VWP IS ADVECTING ANOMALOUS
MOISTURE NORTHWARD...WITH PRECIPITABLE WATER VALUES AROUND 2" PER
GPS...WHICH IS RIGHT AROUND THE CLIMATOLOGICAL MAX FOR LATE
OCTOBER. INSTABILITY PER SPC MESOANALYSIS IS BELOW 1000 J/KG...BUT
THIS IS ENOUGH TO MAINTAIN CONVECTION GIVEN THE STRONG DIVERGENCE
ALOFT AND ENVIRONMENTAL WIND SHEAR PRESENT. THE QUICK MOTION OF
THE LINE WILL LIMIT THE TIME ANY ONE LOCATIONS SEES HEAVIER RATES.
HOWEVER THE ANOMALOUS PRECIPITABLE WATER AND DEEP WARM LAYER IS
ALLOWING FOR EFFICIENT RAINFALL. OBSERVATIONS SHOW AMOUNTS AS HIGH
AS 2"-2.5" WITH THIS LINE...FALLING IN AROUND OR JUST OVER AN
HOUR. NSSL QPE DATA SUGGESTS ISOLATED AMOUNTS AS HIGH AS 3" AN
HOUR MAY BE FALLING WITHIN THIS LINE. 

THESE AMOUNTS ARE RIGHT AROUND THE FLASH FLOOD GUIDANCE ACROSS
SOUTHEAST MS INTO SOUTHWEST AL AND THE FL PANHANDLE...AND THUS
FLASH FLOODING WILL REMAIN POSSIBLE AS THE LINE PROGRESSES INTO
THESE AREAS. NONE OF THE HIGH RESOLUTION GUIDANCE IS REALLY DOING
A GREAT JOB WITH THIS CONVECTIVE LINE. THE 12Z ARW ACTUALLY IS
PRETTY CLOSE WITH THE LINE PLACEMENT...BUT SEEMS TO FOCUS HIGHER
QPF TOTALS TOO FAR NORTH ACROSS AL WHERE INSTABILITY IS EVEN
WEAKER. THINK IT MAY ALSO WEAKEN THE LINE TOO QUICKLY...ALTHOUGH A
DECREASE IN COVERAGE OF COLDER CLOUD TOPS ON LATEST IR MAY BE A
SIGN THE LINE IS PAST ITS PEAK INTENSITY. THUS THE EASTWARD EXTENT
OF THE FLOOD RISK IS UNCERTAIN AS THE LINE SHOULD OUTRUN THE
BETTER INSTABILITY AND LOW LEVEL INFLOW IS FORECAST TO WEAKEN.

CHENARD

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

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

LAT...LON   32588759 32428630 32328608 31618528 30698527 
            30288583 30338726 30378779 30528816 30648856 
            30818879 31138862 31668856 32548819