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FXUS61 KOKX 232013

Area Forecast Discussion
National Weather Service New York NY
413 PM EDT Tue May 23 2017

Weak high pressure moves east of the waters tonight. A low 
pressure system tracks southeast of Long Island late tonight 
into Wednesday morning. Weak high pressure builds in later 
Wednesday, followed by a slow moving low pressure system
affecting the area Thursday into Friday. Weak high pressure 
returns for Saturday. Another frontal system affects the area 
for the latter half of the holiday weekend. 


Anomalously large and deep upper trough and associated upper 
low digs into the the Central US tonight...with jet streak and 
shortwave riding up the coast late tonight into Wednesday 
morning. In response...southern low pressure tracks to the Mid- 
Atlantic coast tonight and then quickly near of just se of the 
40/70 lat/lon Wed morning. 

Still quite a bit of spread in terms of areal coverage of
rainfall between models. A rather tight gradient of heavier 
rainfall from frontogenetic zone to the N/NW of the low...which
should mainly stay se of LI. With region in briefly favorable 
left front quad of approaching upper jet streak...have leaned 
towards higher likelihood of light rain for city/coast late 
tonight/early Wed morning...with decreasing chances for 
measurable rain to the North and West. Gusty N/NE winds develop
along the coast late tonight and continue into Wed morning in 
response tot he low as well. 


Anomalously large and deep Central US upper trough and associated 
upper low gradually slides east into the Ohio/Tennessee River 
Valleys Wed into Wed night. 

Initial shortwave/jet streak and resultant coastal low pressure 
departs Wed aft...with brief high pressure building in Wed aft/eve. 
Any rain pushes east early Wed morning...with gusty N/NE winds Wed 
morning gradually subsiding into the afternoon. At least partial  
afternoon clearing should allow temps to rise to near seasonable
levels...upper 60s/lower 70s.

Models in good agreement with increasing potential for rain 
development late Wed Night into Thu morning ahead of approaching
deep closed low with deep layered lift of sub- tropical 
moisture tap. Easterly winds will be increasing as well...with 
tightening gradient between warm front/low pressure to the S/SW 
and Canadian Maritimes high. See TIDES/COASTAL FLOODING for 
associated impacts.


Unsettled pattern for much of the long term. 

High amplitude upper level trough over the eastern two-thirds of the 
country, with its axis stretching from the Central Great Lakes 
region to the Gulf Coast Thursday morning will push east and become 
negatively tilted through the day. This is indicative of a mature 

At the surface, a warm front will approach from the south. However, 
this front looks to remain south of the region, but should provide a 
lifting mechanism. A moist airmass, with dewpoints rising into the 
upper 50s, with some 60 degree dewpoints not out of the question, 
will already be in place. As the upper low with the system moves 
closer to the area, cooler air aloft will provide some elevated 
instability. MUCAPE values of up to 500 J/kg noted in some of the 
models. A period of moderate to briefly heavy rain is possible 
Thursday morning. Right now, just some general thunderstorms are 

Although precipitation fields are not currently indicating a high 
rainfall event for Thursday with flash flooding, there is a low 
probability, given local climatology. The potential for embedded 
convection, PWATS near 1.50", and low pressure moving into the area 
from the west all point to this potential. Although, winds will be 
east, a shift more to the southeast on Thursday would be another 
ingredient favoring excess rainfall. Again, would be more confident 
in flash flooding if QPF was higher and occurring later in the warm 
season, but for now, minor urban and poor drainage flooding seems 
most likely. 

Surface low pressure moves over the area Thursday night, then heads 
northeast, into the Gulf of Maine Friday morning. Light showers will 
continue for Friday on the back side of the low. 

Weak high pressure builds in for Saturday, with another frontal 
system impacting the area Sunday into Memorial Day. 


VFR this evening.  Low pressure passes to the southeast late tonight 
but close enough to impact coastal terminals with a short period of 
MVFR in late tonight and early Wednesday. Patches of light rain are 
expected 07-14z Wednesday morning, mainly near the coast. 

Winds becoming light and variable early this evening...mainly SE 
then N-NE wind increases late tonight and Wednesday morning 10-15KT. 
Gusts 15-20KT possible coastal terminals early Wednesday as the low 
passes east.

     NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component fcsts,
can be found at: 

KJFK TAF Comments: Amendments possible with timing of MVFR
conditions overnight and Wednesday morning.

KLGA TAF Comments: Amendments possible with timing of MVFR
conditions overnight and Wednesday morning.

KEWR TAF Comments: Low chance of MVFR conditions overnight and 
Wednesday morning.

KTEB TAF Comments: Low chance of MVFR conditions overnight and 
Wednesday morning.

KHPN TAF Comments: Low chance of MVFR conditions overnight and 
Wednesday morning.

KISP TAF Comments: Amendments possible with timing of MVFR
conditions overnight and Wednesday morning.

.21z Wednesday...Becoming VFR. NE wind near 10KT becoming SE near 
10KT late.
.Wednesday night-Friday night...MVFR or lower possible. Slight 
chance of thunderstorms Thursday. E winds G20kt with LLWS 
.Sunday...MVFR/IFR developing.


Winds and seas are expected to remain below small craft levels 
through tonight. Overnight, an initially weak pressure gradient
will tighten as an area of low pressure moves up the coast. As 
such, marginal NE SCA winds and seas are likely to develop on the 
ocean late tonight into Wednesday morning. Winds will become light 
by Wednesday afternoon...but seas may remain elevated on the ocean 
through Wednesday night. 

Low pressure will approach the waters Wed Night into Thursday 
Morning with easterly SCA winds likely developing across all 
waters...with a low probability for gale gusts. Winds likely
begin to diminish late Thu into Thu eve. Ocean seas building to
5 to 7 ft Thursday and remain Friday, then diminish to less 
than 5 ft for Saturday and the remainder of the weekend.


0.75" to 1.00" of rain is currently forecast from Thursday 
through the day on Friday. Higher amounts are possible in any 
thunderstorms that develop on Thursday. The potential for flash 
flooding is low given local climatology (see Long Term section) 
and the most likely scenario is minor urban and small stream 
flooding given antecedent wet conditions. 

Another round of light to moderate rainfall is possible for 
beginning of next week.


Increasing threat for successive rounds of minor coastal 
flooding for the Wed Night, Thu Morning and Thu Night high tide
cycles. Greatest threat for widespread minor and potentially 
moderate coastal flooding appears to be with the Thursday 
eve/night high tide cycle as a slow moving low pressure system 
approaches the region...and with less than 1/2 ft of surge 
needed in many places to reach minor flood thresholds and 1 to 2
ft for moderate.


MARINE...Small Craft Advisory from 6 AM Wednesday to 8 AM EDT Thursday 
     for ANZ350-353-355.



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