MESOSCALE PRECIPITATION DISCUSSION 0152...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1101 AM EDT WED JUN 25 2014
 
CORRECTED FOR TYPO IN SECOND PARAGRAPH

AREAS AFFECTED...CENTRAL PA, CENTRAL NY, SOUTHERN VT, NORTHWEST MA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251457Z - 252057Z
 
SUMMARY...BUILDING CAPE VALUES ACROSS A VERY MOIST REGION
INTERACTING WITH STRENGTHENING THERMAL CONTRAST ACROSS CENTRAL PA
AND SOUTHEAST NY COULD ORGANIZE CONVECTION WITH HOURLY RAIN RATES
OF 2" AN HOUR.  SEVERAL INSTANCES OF FLASH FLOODING ARE POSSIBLE.

DISCUSSION...A FRONTAL ZONE IS SLOWLY APPROACHING THE REGION IN
QUESTION, WHICH HAS LURED A DEEP WARM AND MOIST AIRMASS INTO THE
NORTHERN MID-ATLANTIC STATES.  PRECIPITABLE WATER VALUES ARE
1.75-2", WHICH IS ABOVE THE 90TH PERCENTILE FOR LATE JUNE.  SHEAR
IN THE 0-3 KM AND 0-6 KM LAYER IS JUST SUFFICIENT FOR ORGANIZED
CONVECTION AND THE WET MULTI-CELL ENVIRONMENT.  AREA SOUNDINGS
INDICATE THAT WET BULB ZERO HEIGHTS ARE ~14,000 FEET, WELL ABOVE
THE 10,000 FOOT GUIDELINE FOR WARM RAIN PROCESSES, INDICATING THAT
FEW OVERSHOOTING TOPS ARE LIKELY AND RADAR ESTIMATES COULD BE TOO
LOW WITH ANY CONVECTION IN THE REGION.

THERE ARE NO DRY LAYERS NEAR OR BELOW 700 HPA IN AREA SOUNDINGS,
INDICATING THAT COLD POOLS SHOULD NOT ACCELERATE ORGANIZED
CONVECTION.  CORFIDI VECTORS SUGGEST LITTLE MOVEMENT TO ORGANIZED
CONVECTION, SHOWING 5 KTS OF MOTION TO THE EAST-NORTHEAST. 
LESS-ORGANIZED CONVECTION COULD TRAIN DUE TO UNIDIRECTIONAL WINDS
THROUGH THE LOWER AND MIDDLE TROPOSPHERE.  HOURLY RAINFALL RATES
OF 2" ARE EXPECTED IN STRONGER STORMS, WITH THE AVAILABLE
MESOSCALE GUIDANCE AGREEING THAT A QUICK 2-4" IS POSSIBLE LOCALLY
WITHIN THE DEFINED AXIS.  SEVERAL INSTANCES OF FLASH FLOODING ARE
POSSIBLE OVER THE NEXT SEVERAL HOURS, PARTICULARLY OVER THE
NORTHWEST HALF OF THIS AREA WHERE FLASH FLOOD GUIDANCE VALUES ARE
LOWER.

ROTH

ATTN...WFO...BOX...BTV...ALY...BGM...BUF...CTP...PBZ...

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

LAT...LON   42667297 41837532 40917654 39907826 39967942 40767946
            41857847 42997683 43607482 43657283 42667297