MESO: Nws Weather Prediction Center College Park Md

AWUS01 KWNH 192016
FFGMPD
MEZ000-NHZ000-VTZ000-NYZ000-200215-

MESOSCALE PRECIPITATION DISCUSSION 0163
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
416 PM EDT FRI JUL 19 2013

AREAS AFFECTED...MUCH OF ME...NH...VT...NORTHERN NY

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

VALID 192015Z - 200215Z

SUMMARY...A BAND OF CONVECTION ACROSS SOUTHEAST CANADA IS EXPECTED
TO DROP INTO CENTRAL NEW ENGLAND AND NORTHERN NY. DUE TO THE
RELATIVELY LOW FLASH FLOOD GUIDANCE VALUES -- FFGS -- AND RECENT
RAINS ACROSS NORTHERN AND CENTRAL ME, FLASH FLOODING IS POSSIBLE.

DISCUSSION...A WAVY/"LEWP-Y" BAND OF CONVECTION EXTENDING FROM
SOUTHERN QUEBEC INTO SOUTHEAST ONTARIO IS MOVING TOWARDS THE
REGION THROUGH THE WARM SECTOR OF A FRONTAL WAVE. DIVERGENCE
ALOFT HAS BEEN CAUSED BY TROUGHING DEVELOPING UPSTREAM ACROSS
ONTARIO AND LAKE SUPERIOR. INFLOW AND DEEP LAYERED FLOW ACROSS
THE REGION ARE CLOSE TO 50 KNOTS. CAPE VALUES ACROSS THE REGION
ARE IN THE NEIGHBORHOOD OF 2000-3000 J/KG. PRECIPITABLE WATER
VALUES ARE AROUND TWO INCHES WITHIN THE BAND, WHICH IS TWICE THE
NORMAL VALUE AND NEAR THE 90TH PERCENTILE FOR MID-JULY IN THIS
REGION.

THE BAND IS CURRENTLY MOVING AT A SLIGHT ANGLE TO THE MEAN FLOW,
WHICH COULD LEAD TO CELL TRAINING ACROSS THE REGION BETWEEN THE
SMALL CONVECTIVE BOWS WITHIN ITS LEWP -- LINE ECHO WAVE PATTERN.
EARLIER STORMS NEAR QUEBEC CITY EARLY THIS AFTERNOON DISPLAYED
RAINFALL RATES OVER 1.5 INCHES PER HOUR, SO THE POTENTIAL IS THERE
FOR HEAVY RAINS FROM A RAINFALL EFFICIENCY STANDPOINT. THE 15Z
HRRR INDICATES THAT THE CONVECTION SHOULD PERSIST UNTIL ABOUT
01Z/9 PM EDT, THOUGH ITS MOTION LOOKS A BIT TOO SLOW PER RECENT
RADAR TRENDS. THE FFGS ACROSS THE REGION ARE ROUGHLY TWO INCHES IN
THREE HOURS. A QUICK 2-3 INCHES OF RAIN COULD LEAD TO FLASH
FLOODING.

ROTH

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CAR...GYX...BTV...ALY...BGM...BUF...

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

LAT...LON 45956896 45736743 44866684 44166776 43516996 43237265
43347574 43827665 44987564 45867174 45956896

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