MESOSCALE PRECIPITATION DISCUSSION 0696
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 AM EST FRI DEC 25 2015
 
AREAS AFFECTED...CENTRAL AND NORTHEAST AL...CENTRAL AND NORTHERN
GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 250700Z - 251300Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS ARE PERSISTING ALONG AN
AXIS FROM SOUTHEAST MS NORTHEAST ACROSS CENTRAL AL AND INTO
CENTRAL AND NORTHERN GA. GIVEN  VERY WET ANTECEDENT
CONDITIONS...ADDITIONAL FLASH FLOODING APPEARS LIKELY THROUGH THE
EARLY MORNING HOURS.

DISCUSSION...THE LATEST WV IMAGERY DEPICTS A SHORTWAVE IN THE
NORTH-CENTRAL GULF OF MEXICO THAT IS EJECTING TO THE NORTHEAST AND
IS INTERACTING WITH THE REMNANTS OF THE CONVECTIVELY REINFORCED
COLD-POOL BOUNDARY THAT WAS FOCUSED OVER SOUTHEAST AL AND CENTRAL
GA EARLIER IN THE NIGHT. THE BLENDED TPW PRODUCT THOUGH IS SHOWING
A NORTHWARD SURGE OF DEEPER MOISTURE INTO THE GULF COAST STATES
AND LOWER MS VALLEY REGION WITH THE FETCH ROUNDING THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE NOSING WEST INTO THE GULF OF
MEXICO.

PWATS ACROSS THE REGION ARE RUNNING AS HIGH AS 1.6 TO 1.8 INCHES
AND IS AS HIGH AS 3 STD DEV ABOVE NORMAL. THIS ANOMALOUS MOISTURE
CONTINUES TO FAVOR VERY HIGH RAINFALL RATES WHICH ARE LOCALLY
EXCEEDING 2 INCHES/HR. ONCE AGAIN THE DEEPER LAYER FLOW IS RATHER
UNIDIRECTIONAL AND SO CONVECTION THAT CONTINUES TO DEVELOP HAS
BEEN REPEATEDLY IN A POSITION TO TRAIN OVER THE SAME AREA. DEEPER
LAYER ASCENT DOES REMAIN OVER THE REGION IN PART DUE  TO THE
AFOREMENTIONED SHORTWAVE...AND AS PER DISCUSSION WITH
NESDIS/SAB...THE CIMMS AND NOAA/NSSL DIVERGENCE PRODUCT CONTINUES
TO SHOW AN IMPRESSIVE AREA OF UPPER LEVEL DIFFLUENCE EXTENDING
FROM CENTRAL MS EAST INTO SC WHICH COINCIDES WITH MOISTURE SURFACE
CONVERGENCE SEEN OVER SOUTHWEST AL. REGIONAL VWPS IN AL/MS SHOW 25
TO 30 KT SOUTHWEST FLOW AT 850 MB AND THIS IS SUGGESTED BY THE
LATEST CAM GUIDANCE TO PERSIST THROUGH THE EARLY MORNING HOURS.

EXPECT ADDITIONAL CLUSTERS OF CONVECTION TO PERSIST THROUGH 12Z AS
INDICATED BY THE 00Z ARW AND 00Z NMMB...BUT WITH AN AXIS THAT
SHOULD GRADUALLY SHIFT A BIT FURTHER NORTH OVER THE NEXT FEW HOURS
GIVEN SOME STRENGTHENING OF THE MID LEVEL RIDGE OVER THE GULF OF
MEXICO AND SOUTHEAST COASTAL PLAIN.

ADDITIONAL RAINFALL AMOUNTS OF AS MUCH AS 2 TO 4 INCHES WILL BE
POSSIBLE LOCALLY AND THIS WILL RESULT IN ADDITIONAL FLASH FLOODING
GIVEN THE VERY WET ANTECEDENT CONDITIONS.

ORRISON

ATTN...WFO...BMX...FFC...GSP...HUN...MOB...

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

LAT...LON   34928374 34618295 33908270 33238352 32908402 
            32508524 32068658 31828720 31978760 32388763 
            33148689 34468602 34888505