Mesoscale Precipitation Discussion 0658
NWS Weather Prediction Center College Park MD
617 AM EDT Tue Aug 14 2018

Areas affected...north-central PA into west-central NY

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

Valid 141017Z - 141530Z

SUMMARY...Locally concentrated areas of slow moving heavy rain are
likely to continue through late morning across portions of
west-central NY into northern PA. Additional totals of 3-6 inches
will be possible where cells stall the longest, on a localized
basis.

DISCUSSION...KBGM radar imagery over the past 1-2 hours has shown
a small cluster of heavy rain (1-2 in/hr rates) nearly stationary
over Seneca, Yates and Schuyler counties in west-central NY. Local
reports from Wunderground.com indicate 3-5+ inches of rain has
fallen on either side of Seneca Lake where multiple water rescues
are being reported and where a Flash Flood Emergency was issued at
524 AM EDT. This region sits in a favorable spot to the west of an
850-700 mb low located just southeast of Binghamton, within a
TROWAL signature and relatively higher precipitable water values
of 1.5 to 1.8 inches extending southwestward from northeastern NY.
CAPE remains weak across the region, roughly 500 J/kg per the
latest SPC mesoanalysis page, and little change in CAPE is
expected over the next couple of hours given cloud cover.

Slow pivoting of a favorable 700-500 mb theta-e axis is
anticipated over the next 2-4 hours with the portion near Lake
Ontario translating westward, while some slight eastward movement
near the NY/PA border is anticipated as the 700 mb low slowly
adjusts northeastward through 18Z. Expect the continued
development of slow moving or nearly stationary cores of heavy
rain to develop/dissipate with rainfall rates of 1-2 in/hr across
portions of west-central NY into north-central PA with localized
totals of 3-6 inches possible through 16Z. Given the saturated
soils in place, especially across northern PA into the first row
or two of counties in west-central NY, flash flooding is
considered likely, possibly significant, although it is not
expected to be widespread across the entire MPD threat area.

Otto

ATTN...WFO...BGM...BUF...CTP...

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

LAT...LON   43517676 43317621 42757617 42387567 41897549
            41477591 41307643 41257705 41547769 42127797
            42737793 43267744