000
FXUS61 KOKX 231956
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
356 PM EDT Wed Aug 23 2023
.SYNOPSIS...
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High pressure moves offshore tonight. Low pressure and its
associated warm front slowly approach Thursday into Thursday
night, potentially lingering over the area into Friday. A
couple of cold fronts move through Saturday into Saturday night.
High pressure builds in for Sunday through Monday. A slow
moving frontal system will approach for Tuesday and Wednesday.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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High pressure will shift offshore tonight. The region will
continue to lie within NW flow aloft between the large heat
ridge over the central states and the upper trough over SE
Canada and the North Atlantic. Low pressure over the Great Lakes
will start to approach late tonight as a shortwave impulse
dives towards the area within the NW flow aloft. The wave is
flat at 500 mb, but is more apparent closer to 850 mb where a
more well define trough axis sets up over Central PA and western
Upstate NY. CAMs indicate a decaying convective complex will
move along this axis, staying well to our west. However, clouds
will start to increase through the night. The clouds may have a
tougher time lowering/thickening further east closer to the
surface ridge axis. Mainly dry conditions are forecast, but will
show a slight chance towards day break for Orange and W Passaic
as this is where saturation and lift may support a brief
shower.
Otherwise, lows will range from the upper 50s inland and LI
Pine Barrens to the lower and middle 60s elsewhere.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
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The center of the surface high will lie just off the New
England coast Thursday. The low pressure over the Great Lakes
will slowly approach along with its associated warm front. The
low level wind profile is indicative of a classic warm advection
pattern helping to saturate the low levels and allow for
showers to develop in the morning into the afternoon, mainly
from along the Hudson River corridor on west. These showers are
likely to develop along and east of a tight thermal gradient at
850 mb with temperatures in central PA progged to be around
15-18C and only around 8-10C along and west of the Hudson River.
It may be a bit more difficult for showers to develop further
east closer to the ridge axis with low level dry air hanging on
into the afternoon and early evening out. Will show likely PoPs
for the western half of the area late morning into the
afternoon, tapering down to chance and slight chance further
east. Model soundings show steepening low level rates, but a
strong cap/inversion around 700 mb. Removed mention of thunder
during the day on Thursday as there is no notable instability
present on forecast soundings. Rainfall amounts through
Thursday afternoon will generally be light and a quarter inch or
less. Warm rain processes and a deepening warm cloud layer
support some spots seeing locally higher amounts.
Main area of uncertainty for Thursday night revolves around
potential development of a convective complex to our west. CAMs
are starting to come into better agreement that this will occur
along the continued steep 850 mb temperature and instability
gradient to our west. The associated surface low and warm front
continue approach into early Friday morning so it is possible
portions of the area get clipped by this complex. At the same
time, overrunning, deep warm cloud layer, and strengthening low
level jet support shower development outside well east of the
potential convective complex. The middle level inversion looks
to persist based on the latest forecast soundings, but
instability aloft increases through the night. There is still a
risk of locally heavy downpours and WPC has continued with the
marginal risk of excessive rainfall for much of the area. It is
uncertain if the warm front fully moves through or will remain
near or just south and west of the area by Friday morning. Will
have to watch trends in the CAMs and guidance on the
aforementioned convective complex potential, but based on
current consensus of guidance any severe threat looks to reside
west of the CWA into early Friday morning. Rainfall amounts on
average around one half inch are forecast Thursday night, but
locally higher amounts are possible where any heavier downpours
end up occurring.
The warm front should slowly move into the area on Friday, but
uncertain if it fully pushes to the east. It could linger across
eastern areas into the afternoon. The bulk of the larger scale
lift should lift to the NE by Friday afternoon. There is still
potential for some locally heavy downpours Friday morning across
eastern LI and SE CT. Forecast soundings indicate the rest of
the area will see the middle levels dry out with just some
lingering low level moisture on Friday. Will keep chance PoPs
areawide Friday afternoon since the 850 mb trough axis remains
nearby, but could see much of the area with mainly dry
conditions.
Highs Thursday will be below normal due to onshore flow, clouds,
and precip. Some warmer air reaches the area Friday, but could
still end up slightly below normal for this time of year.-- End Changed Discussion --
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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Zonal flow aloft Friday night will be replaced by late
Saturday into Saturday night. At the surface, one cold front
will be offshore as another one approaches from the west on
Saturday. There is a fair amount of uncertainty with these
features among the deterministic models, so stuck fairly close
to the NBM POPs. Kept at least slight chance POPs from late
Friday night through the first half of Saturday night (despite
some regions of the forecast area being dry according to NBM)
due to the fact that there will be a frontal boundary offshore
and another approaching from the west during this time frame.
There may very well be a lull as the NBM suggests, but when and
where is unknown at this time.
High pressure builds in for Sunday through Monday, then retreats
into the Canadian Maritimes on Tuesday. Meanwhile, Tropical
Cyclone Franklin will move northward over the western Atlantic
(staying well offshore). In terms of indirect impacts, swells
from tropical cyclone Franklin will likely build late Monday
into Tuesday and continue into mid week, bringing increasing
potential for dangerous rip currents and high surf. Models seem
to be hinting at a potential PRE event with the cyclone, as the
area comes under the right entrance region of a 200 hPa jet
Wednesday morning, along with a 925 hPa equivalent potential
temperature ridge east of a 700 hPa trough as per the GFS. Will
obviously have to continue to monitor this feature as it is
climatologically favorable and associated with heavy rain.
Rain begins to move in from the west late Monday night into Tuesday
morning and lasts through the end of the forecast period.
Monitor https:/www.weather.gov/okx/tropical for the latest NHC
forecasts on this tropical system and others.-- End Changed Discussion --
&&
.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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High pressure retreats farther offshore, while a warm front
approaches from the west through Thursday.
This will be mainly a VFR forecast with a lowering mid deck
tonight. Showers develop, especially after 12Z, for the NYC and
Lower Hudson Valley terminals. For the 30h TAF sites, MVFR
conditions are forecast to develop Thursday afternoon. For the
eastern terminals, a spotty shower cannot be ruled out Thursday
morning.
S/SE winds at 5-10 kt will become light southerly or light and
variable this evening/tonight. Wind will then increase after 12Z
Thursday, increasing to 10-13 kt by afternoon with gusts up to 20 kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
No unscheduled amendments expected.
OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday Afternoon: Showers with MVFR development likely for western
terminals, particularly in the afternoon. S-SE gusts around 20 kt.
Thursday Night-Friday: MVFR or lower likely. Showers with possible
thunderstorms, especially Thursday night into early Friday
afternoon. S/SE gusts 20-25 kt into Friday morning.
Saturday: VFR, Isolated shower or thunderstorm possible.
Sunday and Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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High pressure over the waters tonight into Thursday will
lead to conditions remain below SCA levels. Strengthening SE-S
flow ahead of an approaching warm front late Thursday afternoon
and especially Thursday night will lead to winds 25-30 kt and
ocean seas building to around 5-6 ft. These conditions likely
linger on Friday and could even impact eastern LI Bays and
eastern LI Sound. Winds look to fall below 25 kt in the
afternoon, but ocean seas will likely remain elevated.
Sub SCA conditions expected Friday night through the weekend on
all waters (although ocean seas may run 3-4 ft in long period
SE swell), with a weak pressure gradient regime.
Long period SE swells likely build in from tropical cyclone
Franklin late Monday into Tuesday, likely bringing a return of
SCA conditions on the ocean.-- End Changed Discussion --
&&
.HYDROLOGY...
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Showers and a few thunderstorms Thursday night into Friday
morning. Locally heavy downpours are possible with the main
risk being minor urban and poor drainage flooding. An isolated
flash flood occurrence cannot be ruled out.
No hydrological concerns at this time from Friday night through
the middle of next week. Large uncertainty exists with any
potential heavy rain Tuesday into Wednesday of next week.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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A low risk of rip currents continues into this evening.
The risk of rip current development likely increases from low to
moderate for all beaches on Thursday, with strengthening SE/S winds
and building southerly wind waves. Rip current risk could
potentially increase to high at the beaches of NYC and western
Long Island late aft/early eve as winds increase towards SCA.
A high rip current risk is likely Thursday night into Friday
with 5 ft+ southerly wind waves, possibly lingering into
Saturday.
Swells from tropical cyclone Franklin will likely build early
next week, with increasing potential for high surf and
dangerous rip currents.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JP/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...JP
AVIATION...DW
MARINE...JP/DS
HYDROLOGY...JP/DS
TIDES/COASTAL FLOODING...