MESOSCALE PRECIPITATION DISCUSSION 0469
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
814 AM EDT WED AUG 26 2015
 
AREAS AFFECTED...DOWNEAST MAINE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 261200Z - 261800Z
 
SUMMARY...VERY HEAVY RAINFALL IS LIKELY TO CONTINUE THROUGH THE
MORNING HOURS...WITH LOCALLY EXTENSIVE RUNOFF PROBLEMS AND FLASH
FLOODING POSSIBLE.

DISCUSSION...RADAR IMAGERY SHOWS A BAND OF VERY HEAVY SHOWERS AND
THUNDERSTORMS TRAINING OVER THE SAME AREA ACROSS SOUTHERN
WASHINGTON COUNTY IN DOWNEAST MAINE. THE SATELLITE SIGNATURE HAS
BECOME A BIT MORE CONCERNING OVER THE LAST HOUR AS CLOUD TOP
TEMPERATURES HAVE BEEN COOLING FURTHER...AND THERE HAS BEEN AN
INCREASINGLY DIFFLUENT CHARACTER TO THE CLOUD SIGNATURE AS A
SHORTWAVE IMPULSE LIFTS NORTHEAST FROM SOUTHERN NEW ENGLAND.

DEEP MOISTURE IS IN PLACE ACROSS THE REGION WITH PWATS OVER 1.5
INCHES AS PER LATEST GOES-SOUNDER DATA...AND A NOTABLE CHANNEL OF
MOISTURE TRANSPORT NOTED IN THE 850MB/700MB LAYER WHICH IS
WELL-DEFINED IN THE LATEST CIRA LAYERED PWAT PRODUCT. THE
AFOREMENTIONED SHORTWAVE OVER SOUTHERN NEW ENGLAND IN ADDITION TO
FACILITATING LARGER SCALE ASCENT...IS ALSO HELPING TO FOCUS A WAVE
OF LOW PRESSURE ALONG A FRONTAL ZONE. THIS WILL CONTINUE TO HELP
FOCUS/CHANNEL MOISTURE INTO DOWNEAST MAINE THROUGHOUT THE
MORNING...AND THE ONGOING CONVECTION IS LIKELY TO BE SUSTAINED AS
A RESULT AND MAY EXPAND IN COVERAGE.

THE HIRES MODELS ARE NOT HANDLING THE CURRENT LEVEL OF CONVECTIVE
ACTIVITY PARTICULARLY WELL...BUT THE 00Z ARW/00Z NMMB AND 00Z
NSSL-WRF ALL AT LEAST DEPICT THE CHANNELING OF MOISTURE AND A FEW
LINEAR BANDS OF CONVECTION ACROSS PORTIONS OF NORTHERN NEW ENGLAND
AND ESPECIALLY CENTRAL AND EASTERN MAINE BETWEEN 12Z AND 18Z.

GIVEN THE ENVIRONMENTAL CONDITIONS...EXPECT VERY HEAVY SHOWERS AND
THUNDERSTORMS TO PERSIST THROUGH THE MORNING HOURS WITH VERY HEAVY
RAINFALL RATES OF UP TO 2 INCHES/HR. UP TO 3 TO 5 INCHES OF RAIN
HAS ALREADY FALLEN LOCALLY AS PER DUAL-POL ESTIMATES...BUT AN
ADDITIONAL 2 TO 4 INCHES WILL BE POSSIBLE THROUGH MID TO LATE
MORNING...AND THUS THE THREAT FOR LOCALLY EXTENSIVE RUNOFF
PROBLEMS AND FLASH FLOODING WILL PERSIST.

ORRISON

ATTN...WFO...CAR...GYX...

ATTN...RFC...NERFC...

LAT...LON   46656798 46436732 45876691 45056680 44496728 
            43976829 43966869 44476935 45936885