MESOSCALE PRECIPITATION DISCUSSION 0179
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1038 AM EDT FRI JUL 26 2013
 
AREAS AFFECTED...EASTERN ME 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 261437Z - 262037Z
 
SUMMARY...FOCUSED LIFT OF ANOMALOUSLY MOIST AIR OVER DOWN EAST
MAINE WILL BRING A POSSIBILITY OF FLASH FLOODING.

DISCUSSION...THE SYNOPTIC SETUP FOR THIS PRECIPITATION EVENT WAS
EASILY EVIDENT. AND ON THE MESOSCALE THERE WAS AN INCREASING
NUMBER OF CLUES FROM OBSERVATIONS AND MODELS SUGGESTING A FOCUSED
PERIOD OF HEAVIER RAIN RATES WILL OCCUR OVER EAST/SOUTHEAST ME
TODAY.

AT 14Z...SATELLITE SHOWED INCREASING COVERAGE OF DEEPER CONVECTION
OFFSHORE. RADAR IMAGERY REVEALED A BROAD MESO-VORTEX OFF SOUTHERN
ME WHERE CONVECTION AND RELATED HEAT RELEASE MAY BE ENHANCING THE
PRE-EXISTING LARGER SCALE VORTICITY MAXIMUM. LOW LEVEL WARM
ADVECTION WILL PUMP AIR WITH PW VALUES NEAR 2 OR 2.25 INCHES INTO
SOUTHEAST ME AHEAD OF THE VORT MAX. FROM THE GEFS...
CLIMATOLOGICAL DEVIATION OF PW PEAKING AT 2.5 STANDARD DEVIATIONS
AND 850 MB MOISTURE TRANSPORT PEAKING AT 3-4 DEVIATIONS ARE QUITE
FOCUSED IN TIME AND SPACE. AGREEING WITH THE GFS/GEFS...THE HRRR
PREDICTS 1"/HOUR RATES DURING THE PEAK OF THE EVENT...WHICH MAY
SPAN A 3-5 HOUR PERIOD.

THE GREATEST RAINFALL...WITH TOTALS EXCEEDING 3 INCHES
LOCALLY...IS EXPECTED IN WASHINGTON AND HANCOCK COUNTIES...WITH
SOMEWHAT LESSER AMOUNTS IN ADJACENT COUNTIES NORTH AND WEST.
RAINFALL THROUGH 14Z HAD BEEN FAIRLY LIGHT...EXCEPTING ONE GAUGE
AT EASTPORT ME WHERE 1.86" WAS OBSERVED SINCE MIDNIGHT. THROUGH
FLASH FLOOD GUIDANCE VALUES ARE NOT PARTICULARLY LOW...THIS
APPEARS TO BE A LONGER DURATION EVENT THAT MAY MEET 3 OR 6 HOUR
GUIDANCE AND PRODUCE FLASH FLOODING. THE FOCUSED PORTION OF THE
EVENT IS EXPECTED TO EXIT ME TOWARD THE NORTHEAST BY 21-22Z.

BURKE

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

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

LAT...LON   43086795 43056924 43756963 44786929 46206828 46526687
            45226601 43546707 43086795