MESOSCALE PRECIPITATION DISCUSSION 0456
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1251 PM EDT SAT JUL 08 2017

AREAS AFFECTED...MAINE

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

VALID 081650Z - 082200Z

SUMMARY...BRIEF TRAINING OF RAINFALL RATES 1 TO 1.5 IN/HR IS
EXPECTED TO PRODUCE A STRIPE OF LOCALLY HEAVY RAIN AND POSSIBLE
FLASH FLOODING ACROSS PORTIONS OF CNTRL AND NRN MAINE THROUGH 22Z.

DISCUSSION...WATER VAPOR IMAGERY AT 16Z INDICATED A POTENT
MID-UPPER LEVEL SHORTWAVE OVER THE SRN ONTARIO/QUEBEC BORDER
TRACKING EAST. RAP ANALYSES INDICATED AN 850 MB LOW WAS LOCATED
ABOUT 40 MI SOUTH OF QUEBEC CITY AT 16Z AND WAS ASSOCIATED WITH A
REGION OF STRONGER 850 MB FLOW TO ITS
SOUTH/SOUTH-SOUTHEAST...25-30 KT. THE 850 MB LOW IS FORECAST TO
TRACK ENE THROUGH 00Z WITH THE CORRIDOR OF STRONGER LOW LEVEL FLOW
MOVING ACROSS CNTRL AND NRN MAINE LATER THIS AFTERNOON. AREA
RADARS AT 1630Z SHOWED A BROKEN LINE OF SHOWERS AND THUNDERSTORMS
MOVING EAST ACROSS NWRN MAINE WITH INCREASING INTENSITY OVER THE
PAST HOUR.

WHILE INSTABILITY IS LOW ACROSS NRN MAINE...BREAKS IN CLOUD COVER
HAVE ALLOWED FOR A LITTLE SOLAR INSOLATION ACROSS THE REGION AND
MLCAPE VALUES ARE ESTIMATED TO RANGE FROM 250 TO 750 J/KB PER THE
LATEST SPC MESOANALYSIS ACROSS WRN AND NRN MAINE. WHILE
PRECIPITABLE WATER VALUES ARE EXPECTED TO REMAIN ONLY MODESTLY
ANOMALOUS...1.25 TO PERHAPS 1.5 INCHES THIS AFTERNOON PER THE
LATEST SHORT TERM MODEL FORECASTS...ENOUGH MOISTURE AND
INSTABILITY ARE PRESENT TO SUPPORT LOCALLY HEAVY RAINFALL RATS OF
1 TO 1.5 IN/HR WHEN COUPLED WITH STRONGER LOW LEVEL INFLOW AHEAD
OF THE 850 MB LOW.

THE MAIN CONCERN FOR FLASH FLOODING IS DUE TO AN AREA LOW FLASH
FLOOD GUIDANCE...1 TO 1.5 IN/HR AND 1.5 TO 2.0 INCHES IN 3 HOURS
ACROSS PORTIONS OF CNTRL AND NRN MAINE. WHILE NOT EXPECTED TO BE A
SIGNIFICANT FLASH FLOOD EVENT...LOCAL RUNOFF ISSUES MAY ARISE
THROUGH ABOUT 22Z...AT WHICH POINT DRIER AIR SHOULD BEGIN
ADVECTING IN BEHIND A COLD FRONT.

OTTO

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

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

LAT...LON   47266779 46946736 46176759 45026886 44927017
            45827037 46486999 47036887