244
AWUS01 KWNH 271608
FFGMPD
NYZ000-NJZ000-PAZ000-272200-

Mesoscale Precipitation Discussion 0333
NWS Weather Prediction Center College Park MD
1208 PM EDT Mon May 27 2024

Areas affected...Eastern Upstate NY...Eastern PA...Western NJ...

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

Valid 271615Z - 272200Z

SUMMARY...A few rounds of heavy rainfall pose spots of 2-3", some
spots up to 1.75"/hr may induced widely scattered incidents of
flash flooding through the afternoon into early evening hours.

DISCUSSION...GOES-E WV denotes a potent longwave trof over the
Great Lakes with a compact upstream kicker to further sharpen the
wave throughout the day.  This timing/orientation is also
supporting the leading edge of the modified EML to sharpen a
shortwave trough across the the upper Ohio Valley providing
strengthening broad scale ascent/DPVA downstream.  Additionally,
this is drawing deeper, more unstable, higher theta-E air off the
eastern Atlantic becoming increasingly confluent with moisture
stream emerging out of the Cumberland Plateau through the
Mid-Atlantic.  A subtle southern stream shortwave has lifted
northward across Northern VA/Central MD,  further helping
height-falls as well as backing and strengthening low level wind
fields.  As such, total PWAT values are inching up to 1.5-1.75"
across Central PA, Delaware River Valley and leaking into the
Hudson Valley over the next few hours.

RAP analysis also notes increasing MUCAPE along/ahead of the
weakening southern stream warm front currently reaching 750-1000
J/kg.  Further downstream clearing but also steepening lapse rates
with some eastern edge of the modified EML nosing in, should allow
for CAPEs to reach 1000-1500 by mid-afternoon across the area of
concern.  Current RADAR shows some increasing congestion across
the area of greatest ascent, as well as, along the western edge of
the mid-level stratus in Central PA.  Hi-res CAMs remain bullish
on rapidly intensifying updrafts through this sector.  Given
available moisture, unstable air and flux, expectation is for
rapid efficient rainfall production with 1.5-1.75"/hr rates likely
to become frequent in the warm sector line from SE Upstate NY into
E PA over the next 2 hours.  Streaks of 2" in 1-2hrs are possible
with southern/upstream edge of convective line having best chances
for back-building short-term training before western cells
approach.  Flash flooding is not necessarily expected with this
line with the exception of urban centers with hydrophobic ground
conditions that support high runoff.

However, upstream, the approaching secondary line should also be
intensifying through late afternoon. While deeper layer steering
should allow for faster and more west to east cell motions, and
additional 1-2" stripes with the intense downdrafts may intersect
with earlier round and result in widely scattered 2-3" totals in
3-4hrs resulting in possible widely scattered incidents of flash
flooding to occur; particularly in complex terrain of NE PA, SE NY
and NW NJ.

Gallina

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

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

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

LAT...LON   43537427 42977371 41637376 40257473 39797608
            40177662 40887676 41937686 42817651