MESOSCALE PRECIPITATION DISCUSSION 0701
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
102 AM EST SAT DEC 26 2015
 
AREAS AFFECTED...CENTRAL AL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 260600Z - 261000Z
 
SUMMARY...BACK-BUILDING SHOWERS AND THUNDERSTORMS CONTINUE TO
FOCUS VERY HEAVY RAINFALL...WHICH IS EXACERBATING ONGOING
SIGNIFICANT FLASH FLOODING CONCERNS.

DISCUSSION...THE LATEST IR SATELLITE IMAGERY CONTINUES TO SHOW
COLD-TOPPED CONVECTION PERSISTING OVER CENTRAL AL WHERE VERY HEAVY
RAINFALL OVER THE LAST COUPLE OF DAYS HAS ALREADY LED TO LOCALLY
SIGNIFICANT FLASH FLOODING.

THE ACTIVITY IS BEING FACILITATED BY A PERSISTENT AND DEEP
SOUTH/SOUTHWEST FETCH OF VERY MOIST AND MODESTLY UNSTABLE AIR
EMANATING FROM THE GULF OF MEXICO WHICH IS INTERACTING WITH A
CONVECTIVELY REINFORCED OUTFLOW BOUNDARY AND COLD POOL OVER THE
REGION. AREA VWP DATA INDICATES A LOW LEVEL FEED OF ABOUT 20 TO 30
KTS INTO THIS BOUNDARY.

MEANWHILE...IR/WV IMAGERY SUGGESTS A PERSISTENTLY DIVERGENT UPPER
AIR FLOW PATTERN OVER THE REGION WHICH IS BEING CONFIRMED BY THE
DIVERGENCE WIND PRODUCT AS PER COORDINATION WITH NESDIS/SAB. THIS
IS ALLOWING FOR A CONTINUATION OF DEEPER LAYER ASCENT WHICH IS
HELPING TO ENHANCE THE CONVECTIVE REDEVELOPMENT OVER THE REGION.

THE HIRES GUIDANCE INSISTS ON THE CONVECTION WEAKENING OVER THE
NEXT FEW HOURS...AND THERE IS ALREADY SOME HINT OF CLOUD TOP
WARMING THE LAST HOUR OR SO OVER CENTRAL AL. HOWEVER...SUFFICIENT
MOISTURE/INSTABILITY TRANSPORT WITH PWATS  OVER 1.75 INCHES AND
MUCAPE VALUE OF 500 TO 1000 J/KG OVER SOUTHWEST AL WILL LIKELY
MAINTAIN SOME CONVECTION ON A SOMEWHAT SMALLER SCALE THROUGH THE
BALANCE OF THE NIGHT DESPITE THE ACTIVITY TENDING TO WEAKEN
OVERALL.

EXPECT ADDITIONAL RAINFALL AMOUNTS OF LOCALLY 1 TO 3 INCHES OVER
THE NEXT FEW HOURS...WHICH WILL ONLY EXACERBATE THE VERY SERIOUS
RUNOFF PROBLEMS AND FLASH FLOODING THAT HAS ALREADY OCCURRED.

ORRISON

ATTN...WFO...BMX...MOB...

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

LAT...LON   33658615 33458567 32598646 31998733 31908775 
            32208785 32558768 33018711