026
AWUS01 KWNH 291941
FFGMPD
NYZ000-NJZ000-PAZ000-300000-

Mesoscale Precipitation Discussion 0341
NWS Weather Prediction Center College Park MD
340 PM EDT Wed May 29 2024

Areas affected...Northern to Northeast PA...Southern Upstate
NY...Northern NJ...

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

Valid 291940Z - 300000Z

SUMMARY...Steepening ascent pattern with colliding features may
result in short-duration uptick of updrafts with quick downdrafts
capable of highly focused 1-1.75" totals in less than an hour.
Given lower FFG in complex terrain, an incident or two of flash
flooding is possible.

DISCUSSION...GOES-E WV shows a compact inner core to the shortwave
across SW PA with an elongated shear axis up and downstream across
NE OH into NE PA/N NJ.  As a result, broad SSW return, warm
advection exists across Northern PA.  At the surface an associated
cold front and low-level CAA is dropping south across central
Upstate NY.  As such, the combination of the two is resulting in
strengthening FGEN ascent pattern with steepening isentropes for
greater vertical ascent even with modest lapse rates.

CAPE is around 750-1000 J/kg to support narrow but intense
updrafts.  Given deep layer moisture is modest ~1" , it is
maximized along the deformation zone and will support 1-1.5"/hr
though given the broad area of ascent and slow cell
motions/chaotic interaction some mergers/collisions are possible
bringing totals toward the 1.5-1.75" range in about 1 hour time.
FFG values are naturally lower across the region and these rates
would possibly exceed them in these localized intense downdrafts.

Currently the intersection of the deeper layer colliding
boundaries is best maximized further west into north-central PA,
but will continue zipper toward the east into the Poconos and
perhaps southern Catskills and northern NJ terrain toward later
this evening. Currently this area is more cloud free to allow for
some increased insolation perhaps resulting in some slightly
increased instability for  broader updrafts; and therefore broader
areal coverage of those 1-1.5" totals.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...BGM...CTP...OKX...PHI...

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

LAT...LON   42187642 42157545 41707468 41247455 40647477
            40557550 40737694 40967785 41087820 41217850
            41427885 41717877 41937768