MESOSCALE PRECIPITATION DISCUSSION 0102
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1003 PM EDT SAT APR 14 2018

AREAS AFFECTED...AL...SRN MS...FAR ERN LA...FAR WRN GA AND FL

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 150202Z - 150802Z

SUMMARY...INTENSE RAIN RATES WILL SLOWLY MOVE INTO SOUTHERN AND
EASTERN ALABAMA AND ADJACENT FL/GA. LOCALLY RAPID ACCUMULATIONS OF
2 TO 4 INCHES MAY LEAD TO FLASH FLOODING. MEANWHILE ONGOING FLASH
FLOODING IN SOUTHWEST AL / SOUTHERN MS MAY WORSEN AS MODERATE RAIN
AND ASSOCIATED STREAM RESPONSE CONTINUES.

DISCUSSION...AT 0145Z A LINEAR MCS EXTENDED FROM MOBILE BAY TO THE
SOUTHEAST SIDE OF BIRMINGHAM. EARLIER THIS LINE WAS VERY SLOW
MOVING...PRODUCING A SWATH OF OBSERVED 4 TO 6 INCH RAINFALL AND
RADAR ESTIMATED SWATHS OF 8-PLUS INCHES FROM NEAR GULFPORT MS TO
SOUTHWEST AL. CONTINUED RESPONSE AT THE GROUND LEVEL...ALONG WITH
NIGHTFALL MAKING THE DANGERS DIFFICULT TO RECOGNIZE...WILL LIKELY
MAINTAIN A FLASH FLOOD RISK AS MODERATE RAIN AND OCCASIONAL
HEAVIER DOWNPOURS CONTINUE OVERNIGHT.

THE REGION OF GREATEST TRAINING HAD SHIFTED TOWARD BIRMINGHAM AND
ITS SOUTHERN SUBURBS. INSTABILITY WAS SOMEWHAT LESS HERE COMPARED
TO THE COAST...BUT ACCUMULATIONS OF AT LEAST 1.50 INCHES PER HOUR
WERE INDICATED IN DUAL-POL ESTIMATES FROM KBMX. COMPETING
INFLUENCES MAKE THE POSSIBILITY OF NEW FLASH FLOODING NEAR AND
EAST OF BIRMINGHAM SOMEWHAT UNCERTAIN. DRIER MID LEVEL AIR PER
KLCH SOUNDING...COMING AROUND THE BOTTOM OF THE SYNOPTIC TROUGH /
DEVELOPING NEGATIVE TILT...SHOULD FAVOR BETTER PROGRESSION PER
COLD OUTFLOW. INCREASED WARM-SECTOR NOCTURNAL LOW LEVEL
INFLOW...HOWEVER...IS FORECAST TO CAUSE CORFIDI VECTORS TO VEER TO
MORE SOUTHERLY...BECOMING ALIGNED ENTIRELY WITH THE MEAN DEEP
LAYER FLOW. THIS SUGGESTS POTENTIAL FOR PORTIONS OF THE LINE TO
HANG UP AT TIMES...LEADING TO ISOLATED NEW RAIN TOTALS GREATER
THAN 4 INCHES...LIKELY EXCEEDING 3-HOUR FFG IN A FEW AREAS THROUGH
08Z.

THE HRRR HAS HANDLED THE EVENT DECENTLY AS TO PLACEMENT OF THE
HEAVIEST RAIN...THOUGH THE SOMEWHAT IDEAL THERMODYNAMIC
ENVIRONMENT AND WIND PROFILES HAVE LED ALL THE HI-RES MODELS TO
UNDERESTIMATE THE MAGNITUDE OF RAINFALL.

BURKE

ATTN...WFO...BMX...FFC...LIX...MOB...

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

LAT...LON   34008607 33368512 30238696 29648883 29948964
            32788766