Mesoscale Precipitation Discussion 0660
NWS Weather Prediction Center College Park MD
530 PM EDT Tue Aug 14 2018

Areas affected...Northern and Central NY...

Concerning...Heavy rainfall...Flash flooding possible

Valid 142130Z - 150200Z

SUMMARY...Back-building cells within moisture conveyor belt and
slow motions near upper low continue to pose flash flooding risk.

DISCUSSION...CIRA layered PW loops show narrow ribbon of deep
moisture remains connected from Nova Scotia across S Quebec to
Northern and Central NY...with the 7-5H layer representing the
other layers well.   The main upper low is located in Oneida
county with a shortwave lifting north toward Lewis county.  Mild
ridging over Lower MI and general exit region to the synoptic jet
across SE Ontario continues to stretch/narrow the moisture ribbon,
providing some confluence/moisture flux though.  The WV suite from
GOES-16 shows the dry slot over NE NY into VT providing good solar
isolation for instability up to 2000 J/kg which overlaps the
moisture ribbon.  As such the DPVA from the lobe of vorticity
rotating north and left exit to diffluent jet streak over central
New England provides solid ascent.  As such convection has
developed across Lewis and St. Lawrence counties. And given
orientation to low level inflow, cells generally show a
back-building or stationary nature supporting compounding totals. 
With the Total PWATs to 1.5" and strength of updrafts and inflow
from unobstructed clear/unstable areas.  Totals of 2-4" are
possible across Northern NY leading to possible flash flooding.

Further south, a well of deep moisture resides on the southern
side of the main upper low across south central NY into northeast
PA, however this area has been worked over significantly with 5.5
to 6C/km lapse rates but RAP analysis suggests a pocket of
instability remains about 500-750 J/kg. Visible imagery shows some
developing convection further south percolating through older
cirrus.  Cell motions here are a bit more favorable to track
southward toward hardest affected regions where FFG values remain
below .5".  Any cells are likely to reinitiate some flash flooding
conditions, though overall coverage may be spotty and rates of
.5-1"/hr may lead to totals in the range of 1-1.5". 

Gallina

ATTN...WFO...ALY...BGM...BTV...BUF...

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

LAT...LON   44997462 44737410 43977457 43087454 42087465
            41587518 41777663 43097676 43787649 44087634
            44397604 44777550 44917512