MESOSCALE PRECIPITATION DISCUSSION 0413
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1003 PM EDT THU JUN 29 2017

AREAS AFFECTED...NORTHERN NY STATE/NORTHERN VT /NORTHERN NH

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

VALID 300200Z - 300600Z

SUMMARY...CONVECTION MOVING ACROSS AREAS WITH LOWER FLASH FLOOD
GUIDANCE VALUES COULD RESULT IN A FLASH FLOOD THREAT INTO THE
EARLY MORNING HOURS.

DISCUSSION...REGIONAL RADARS ACROSS NORTHERN NEW ENGLAND SHOWED
CONVECTION FORMING AHEAD OF A WEAK SHORT WAVE CROSSING SOUTHEAST
ONTARIO. 00Z SOUNDINGS FROM WMW AND KCAR SHOWED MINIMAL
INSTABILITY AHEAD OF THE SHORT WAVE (NORTH OF A STATIONARY FRONT
ACROSS CENTRAL NY STATE INTO CENTRAL NEW ENGLAND)...WITH MLCAPE
VALUES GENERALLY LESS THAN 500 J/KG.

THE CONVECTION IS FORMING/MOVING ALONG A MOISTURE AXIS...WITH
PRECIPITABLE WATER VALUES NEAR 1.50 INCHES (CONFIRMED BY THE 00Z
WMW SOUNDING). THE CONVECTION IS MOVING FROM WEST TO EAST ALONG AN
ELEVATED BOUNDARY EXTENDING FROM FAR SOUTHEAST ONTARIO INTO
WESTERN ME. THE KTYX RADAR SHOWED HOURLY RAINFALL RATES NEAR 1.25
INCHES...AND CONSIDERING THE DEPTH OF MOISTURE IN THE SOUNDINGS
ACROSS NORTHERN NEW ENGLAND...THESE VALUES SEEM PLAUSIBLE.

THE SHORT WAVE IS EXPECTED TO CROSS NORTHERN NEW ENGLAND THROUGH
06Z. THE SYNOPTIC SCALE ASCENT SHOULD AUGMENT THE MINIMAL
INSTABILITY IN THE MOIST COLUMN TO PRODUCE AREAS OF 1.00 TO 2.00
INCHES OF RAINFALL FROM NORTHEAST NY STATE ACROSS NORTHERN VT. THE
LATEST HRRR SHOWED THIS SCENARIO...AND THE AMOUNTS SEEM REASONABLE
BASED ON WHAT IS OCCURRING UPSTREAM NOW.

ONE HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS 1.00 TO 1.50
INCHES ACROSS A LARGE AREA OF NORTHERN NY STATE INTO NORTHERN VT.
THESE LOWER VALUES SEEM ATTAINABLE AS THE LOW TOPPED CONVECTION
MOVES EASTWARD...SO FLASH FLOODING IS CONSIDERED POSSIBLE INTO THE
EARLY MORNING HOURS. 

HAYES

ATTN...WFO...ALY...BTV...BUF...GYX...

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

LAT...LON   45177152 45007091 44397110 43907367 44047564
            44927532