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Area Forecast Discussion (AFD)

Issued by New York, NY (OKX)

                            
000
FXUS61 KOKX 182101
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
501 PM EDT Tue Jun 18 2019

.SYNOPSIS...
A frontal wave passes near or just south of the area this evening.
The fronts remain in close proximity through Thursday as 
another wave of low pressure passes by the region, along the 
stationary front, Thursday into Thursday Night. The front will 
move offshore Friday, with high pressure returning this weekend.
Another frontal system may approach early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A frontal boundary will remain near just SW of the NYC/NJ metro
this evening, while a frontal wave passes along it. This will
serve as a focus for additional showers and possibly a few 
thunderstorms into early this evening. The greatest instability
resides south of the boundary, along with decent deep-layered 
shear. A few strong and/or severe thunderstorms are possible 
along the boundary, but mainly south and west of the metro 
area. Localized flash flooding is also a possibility in this
corridor.

To the north of the front, elevated instability and frontogenetic
forcing produced a long duration rain event across the Lower 
Hudson Valley and CT. This area will also exit to the east over 
the next few hours. Observations support 1 to 2 inches of 
rainfall from central portions of Orange County in the Lower 
Hudson Valley, to east across interior portions of southern CT.

Any showers/possible thunderstorms will become scattered early
this evening. 

Another mild, muggy night with temperatures in the 60s with
similar dew points. Patchy fog is likely again due to light
winds and low-level moisture.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Warm front is forecast to remain south of the region on 
Wednesday, but will begin to creep back up to the north in the 
afternoon ahead of a deepening upper trough over the mid 
section of the county. Scattered convection is possible as the 
day progresses, but mainly showers as the instability and shear 
will be weak. The one caveat here is that the GFS sets up a 
stronger return southerly flow that hints at the boundary 
getting farther north. This coupled with a more a southerly flow
and stronger diabatic heating differences could be a focus for 
stronger convection north and west of NYC. Locally heavy 
rainfall will be possible with any convection that develops with
PW values remaining around 2 inches.

Highs are forecast to be in the lower and mid 70s. Potential is
there for readings in the upper 70s/lower 80s from the NYC 
metro area north/west and in the interior CT River valley should
the flow take on a more southerly component as suggested by the
GFS. 

There will be a low rip current risk for Atlantic Ocean beaches
on Wednesday.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
The dominant and persistent Eastern Canadian closed upper low, that 
has directed the unsettled weather pattern to the region, will be 
slow to move out of the picture through the weekend. But models are 
signaling potential for upper ridging to build into the area at 
least for a short while late weekend into early next week, before 
the next closed upper low begins to slide east ward from central 
Canada.

Main feature of note for our sensible weather will be shortwave 
energy from an upper trough currently over the SW US, shearing into 
the central US midweek, and then amplifying towards the area by late 
week while interacting/phasing with northern stream energy around 
the eastern Canada closed upper low. This energy will force an 
intensifying low pressure area tracking along the stationary front 
through the Ohio/Tennessee River Valleys on Thursday and likely near 
the region Thu Night/Fri. Still quite a bit of uncertainty at this 
point on the amplitude of the shortwave (likely convectively 
driven), which will affect the track/intensity of this low. Showers 
and tstms are likely with this system Thu afternoon into Thu night. 
Coverage/intensity of shower and thunderstorms, and severe and flash 
flood potential will be driven by amplitude of shortwave and track 
of this low. SPC currently outlooking a marginal potential for 
severe wx from NYC and points west, and WPC a marginal to slight 
risk of flash flooding, which is reasonable based on moisture, lift, 
instability, and wind fields.

In the wake of this system, anomalously deep troughing and deep NW 
flow will bring a dry and seasonable airmass to the region this 
weekend. 

Then potential for a very warm to hot airmass to move into the 
region early next week, but dependent on progressiveness of eastern 
Canadian closed low and amplitude of ridging in its wake.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
A front stalled near the region will keep moisture and light 
and variable winds around 10 kts or less through the TAF period. 
Varying flight categories this evening with stratus and fog...worst 
conditions east of NYC terminals.  LIFR returning again for tonight.

Showers will occur from time to time throughout the TAF period.
There is a slight chance for thunderstorms this evening, at least 
until 23z.  Confidence is very low on placement and occurrence. 
There could be significant changes in category within a small 
distance and the changes in category could occur quite rapidly so 
forecast confidence is low to moderate.

...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component fcsts,
can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: Varying flight categories this evening with 
stratus and fog.

KLGA TAF Comments: Varying flight categories this evening with 
stratus and fog.

KEWR TAF Comments: Varying flight categories this evening with 
stratus and fog.

KTEB TAF Comments: Varying flight categories this evening with 
stratus and fog.

KHPN TAF Comments: Amendments likely due to stratus and fog.

KISP TAF Comments: Amendments likely due to stratus and fog.

.OUTLOOK FOR 21Z WEDNESDAY THROUGH SUNDAY...
.21z Wednesday-Thursday...MVFR or lower. Possible Showers and 
thunderstorms.
.Friday...VFR. Chance of showers.
.Saturday and Sunday...VFR.

&&

.MARINE...
Areas of fog will likely persist across the waters into early
this evening, possibly through the overnight as warm, moist air
moves across the cool waters. Showers and a few thunderstorms 
are likely to provide enough mixing to keep dense fog more 
patchy in nature.

A weak flow across the waters will result in sub-SCA conditions
through Thursday.

Marginal SCA seas possible Thursday night with southerly winds 
waves building to 4 to 5 ft, with better chance of SCA 
conditions area-wide in wake of system Friday with gusty NW 
flow. 

&&

.HYDROLOGY...
An additional 1/2 to 1 inch of rainfall with localized higher
amounts is possible, mainly across the NYC/NJ metro and into 
western portions of Long Island. Localized flash flooding is 
possible.

Another wave of low pressure will likely bring showers and 
thunderstorms for Thursday into early Friday. Rainfall amounts will 
ultimately depend on the track of the low, which remains uncertain 
at this time. Minor urban and poor drainage flooding is the 
predominant threat, but with saturated grounds and streamflows 
running high, a localized flash flooding threat and flashy stream 
flooding threat exists this time.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be relatively high over the next couple
of days due to the recent full moon. This will bring a chance of
localized minor coastal flooding benchmarks being touched 
along the South Shore back bays of Nassau and Queens during the
evening high tide cycles occurring tonight through Thursday 
night. Guidance appears to be running a bit high with recent 
high tides, so have held off on issuing a coastal flood 
statement for this evening's high tide.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off
the air.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...NV/DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...NV
AVIATION...IRD
MARINE...NV/DW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...//
EQUIPMENT...//