MESOSCALE PRECIPITATION DISCUSSION 178
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
652 PM EDT MON MAY 1 2017

AREAS AFFECTED...SOUTH CENTRAL NY AND NORTHEAST PA

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

VALID 012251Z - 020221Z

SUMMARY...A LINE OF INTENSE THUNDERSTORMS WITH HEAVY RAINFALL
RATES OF 1 TO 2 INCHES PER HOUR, FOLLOWED BY LIGHTER STRATIFORM
RAIN, WILL MOVE TOWARDS THE NORTHEAST THROUGH 10 PM LOCAL TIME. 

DISCUSSION...THUNDERSTORMS ASSOCIATED WITH THE FRONTAL BAND MOVING
THROUGH CENTRAL PA AND CENTRAL NY COULD PRODUCE LOCALIZED FLASH
FLOODING DURING THE NEXT SEVERAL HOURS.  THESE STORMS ARE IN A
VERY MOIST AIR MASS WITH PRECIPITABLE WATER VALUES MAINLY IN THE
1.50-1.75 INCH RANGE.  ADDITIONALLY, LOWER FLASH FLOOD GUIDANCE
VALUES EXIST OVER SOUTH CENTRAL NY AND NORTHEAST PA.  A LOW LEVEL
JET OF ROUGHLY 50 KNOTS BASED ON THE RAP GUIDANCE IS EXPECTED THIS
EVENING, SUPPLYING COPIOUS MOISTURE FOR THIS LINE OF CONVECTION.
THE ENVIRONMENT IS MODESTLY UNSTABLE WITH SPC MESOSCALE ANALYSES
INDICATING CAPE VALUES GENERALLY IN THE 500-1000 J/KG RANGE.

ALTHOUGH THE LINE OF CONVECTION IS RELATIVELY PROGRESSIVE, THE
RATES WILL BRIEFLY BE HIGH ENOUGH TO CAUSE SOME CONCERN FOR
PONDING OF WATER AND LOCALIZED FLASH FLOODING.  THE LATEST HI-RES
GUIDANCE SUGGEST RAINFALL OF 1 TO 2 INCHES THROUGH 10 PM, WITH
LOCALLY HIGHER AMOUNTS POSSIBLE. 

HAMRICK

ATTN...WFO...ALY...BGM...BUF...CTP...PHI...

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

LAT...LON   43307593 43187491 42787450 41877457 41297490
            40917516 40567573 40437648 40567690 41137718
            41987699 42747650