Mesoscale Precipitation Discussion 0598...Corrected
NWS Weather Prediction Center College Park MD
427 AM EDT Sat Aug 04 2018

Corrected for Flash Flooding Likely in Concerning Line

Areas affected...Eastern PA...Northern NJ...Southeast NY...Western
CT...Western MA

Concerning...Heavy rainfall...Flash flooding likely

Valid 040814Z - 041330Z

SUMMARY...Slow eastward moving inverted trof/moisture flux band
likely to pose continued flooding threat given saturated soils,
urban environment.

DISCUSSION...08z Surface analysis shows a weak surface wave across
northeast MD into southeast PA. GOES-16 WV suite and 10.3um IR
channel denote a stacked low coincident with a sharp inverted trof
extending northward toward southeast NY.  Goes-16 AMVs and RAP
analysis suggest this shortwave and inverted trough are at the
right exit of a narrow 70kt 3H jet streak, while Blended TPW and
RAP analysis show total the nose of 2"+ PWATs feeding along the
surface wave into the inverted trof.  Weak (500-750 J/kg) uncapped
MLCAPEs are available for some weak vertical development with tops
only reaching -50C.  Given the strong dynamic/thermodynamic
support, these continue to be capable of about 1.25-1.5"/hr rates
and observations bear out about 1-1.25" totals in the last hour
across SE PA to N NJ.  Slow reduction in instability will reduce
convective vigor and depth for high rates, but 1"/hr are likely
through the next 4-6hrs, however, it is the eastward advancement
that is likely to reduce overall totals and limit overall flash
flooding threat.  Still with that stated, low FFG especially
across N NJ into the NYC metro will likely be exceeded and as such
scattered flooding (flashy at times) remains through the early
morning reducing with time at instability minimum. 

Gallina

ATTN...WFO...ALY...BGM...BOX...OKX...PHI...

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

LAT...LON   42627280 42077243 41357300 40727360 40007477
            39877514 39707565 39977586 40757561 41857487
            42617387