MESOSCALE PRECIPITATION DISCUSSION 0417
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
816 AM EDT FRI JUN 30 2017

AREAS AFFECTED...CENTRAL AL...NORTHWEST GA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 301215Z - 301700Z

SUMMARY...DEEP WARM CLOUD PROCESSES LEADING TO EFFICIENT HVY
RAINFALL WITHIN ENVIRONMENT SUPPORTING TRAINING AND BACKBUILDING. 
FLASH FLOODING IS POSSIBLE.

DISCUSSION...WV LOOP DENOTES MAIN SHORTWAVE/WEAK HEIGHT FALLS
SHEARING THROUGH THE CAROLINAS WITH ELONGATED MID-LEVEL SHEAR AXIS
EXTENDING THROUGH N GA /N CENT AL TOWARD S MS.  A LOCAL VORT
MAXIMA IS NEAR THE CENTRAL MS/AL LINE.  THIS DPVA AND 900-600MB
GENERAL CONFLUENCE IN THE VICINITY HAS SPARKED A CLUSTER OF
SHOWERS JUST WEST OF BHM.  RAP ANALYSIS SUGGESTS A SMALL LOCAL
MAXIMA OF ACCESSIBLE INSTABILITY IN A SKINNY VERTICAL PROFILE WITH
VERY HIGH WBZ LEVELS AND SMALL WBZ/FGZ IN A NEARLY SATURATED
PROFILE SUGGESTS EFFICIENT WARM CLOUD PROCESSES.  GIVEN TPWS IN
THE LAYER ARE NEAR 2.25" AND MINOR FLUX...RAIN RATES OF 2.5"/HR
ARE POSSIBLE (WHERE RADAR RAIN RATE ALGORITHMS ARE MORE LIKELY TO
UNDERESTIMATE). ALSO WITH STRONGER UPSTREAM FLOW/CONFLUENCE
C-VECTORS ALSO SUPPORT BACKBUILDING INTO THIS COMPLEX FURTHER
EXTENDING THE DURATION OF HEAVY RAINFALL...POSSIBLY AS GREAT AS
2-4" TOTAL. TO FURTHER COMPOUND THE SITUATION THE CLUSTER IS
MOVING TOWARD LOWERED FFG AREA (BHM METRO) FURTHER INCREASING THE
LIKELIHOOD OF REACHING FLASH FLOODING CONDITIONS.  CURRENT OU
CIMMS FLASH QPE/FFG RATIOS ARE ALREADY AOA 1.0 OVER N TUSCALOOSA
COUNTY.

FURTHER SOUTH...A WEAK LOW-MID LEVEL TRAILING CONVERGENCE TROF IS
SUPPORTING BROKEN CONVECTIVE ELEMENTS ACROSS EAST CENTRAL AL AND
THESE ARE FAVORABLY ORIENTED WITH THE MEAN FLOW TO SUPPORT
TRAINING.  WHILE CONVERGENCE IS LESS (NOTING SLIGHTLY LESS
VIGOROUS UPDRAFTS) RAINFALL EFFICIENCY WILL BE STRONG WITH THESE
CELLS AS WELL ALSO TRACKING THROUGH REDUCING FFG VALUES SUGGESTING
FF IS POSSIBLE HERE AS WELL.  BOTH AREAS ARE FORECAST TO SLOWLY
EXHAUST REMAINING INSTABILITY POOLS AND SLOWLY ADVANCE NE WITH THE
MEAN SHORTWAVE/VORT FEATURES GENERALLY WEAKENING TOWARD THE GA
BOARDER...THOUGH THE NORTHERN COMPLEX GIVEN STRONGER CONVERGENCE
MAY PERSIST LONGER POTENTIALLY AFFECTING N GA HIGHER/COMPLEX
TERRAIN ESPECIALLY IF LOW LEVEL CLOUDS BREAK AND INCREASE
INSOLATION/INSTABILITY IN ADVANCE OF THE WAVE.

GALLINA

ATTN...WFO...BMX...FFC...HUN...

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

LAT...LON   34818444 34578384 33598409 32918467 32308601
            32288677 32548707 33018699 33178764 33658792
            34038750 34618587