Mesoscale Precipitation Discussion 0589
NWS Weather Prediction Center College Park MD
438 AM EDT Fri Aug 03 2018

Areas affected...Central PA...Ext South Central NY...

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

Valid 030838Z - 031230Z

SUMMARY...Increasing convective depth with some training over
saturated soils/low FFG, may lead to some flash flooding through
early morning.

DISCUSSION...Goes-16 3.9um and 10.3um IR, depict a band of cooling
cloud tops to -40C across central PA into south central NY,
generally orienting favorably to the mean cloud bearing flow for
some training to occur.   RADAR suite and VWP suggest the band is
occurring with some weak WAA/isentropic ascent across a subtle low
level boundary from Huntingdon, PA to Sullivan, NY county; in
advance of a weak subtle shortwave inflection emerging from
northern WV.  Fifteen to twenty knots of 850mb flow from the SSW
is not ideally oriented to the band, but is also along crossing a
pool of increased deep moisture per GPS network, where PWATs have
increased to 1.73" near BGM.  This would be confirmed by surface
Tds in the low 70s, and a slug of increased 85-7H moisture per
CIRA LPW and RAP analysis.  Coincident with the increased moisture
are slightly increased mid-level lapse rates providing skinny
instability profiles up to 1000 J/kg. 

The combination with the approach of the subtle wave within the
right entrance to a strengthening upper level jet streak (see
cirrus baroclinic wedge over W PA/E OH) suggests increasing low
level convergence and upper level support for continued convective
development over the next few hours.   Given cloud bearing flow,
even rates of 1-1.25" (given limited instability/low level
heating) for stronger updrafts; saturated soils with FFG values
below 1" across much of the concern area are possible to be
eclipsed especially if coverage increases to support greater
training possibilities through early morning...still this is still
somewhat uncertain given variance in hi-res CAM solutions until
after solar isolation/instability is strengthened.   

Gallina

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

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

LAT...LON   42757520 41837478 40947635 39897794 39827919
            40677870 41687775