000
FXUS61 KOKX 132008
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
408 PM EDT Thu Jul 13 2023
.SYNOPSIS...
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A pre-frontal trough and associated cold front approach from the
north and west this evening. The front then settles over the area
tonight. The front is then expected to remain nearby into Friday
night. Unsettled weather is expected much of the time from Saturday
through Tuesday as a series of frontal boundaries move across the
area. High pressure returns for Wednesday. Another frontal system
may affect the region Thursday.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Sea breeze convergence has been able to develop some isolated
convection near the NYC metro this afternoon. Think this
activity will be short-lived. The main concern continues to be
with the approaching cold front and associated pre-frontal
trough later this evening. A squall-line exists across upstate
NY that will move eastward through this evening. The majority of
the guidance keeps this line to our north before it starts to
weaken with loss of daytime heating as it enters New England.
Some of the CAMs signal some development across the Lower Hudson
Valley this evening as the line starts to pass to the north.
This convection could be briefly strong early this evening with
gusty winds possible and locally heavy downpours.
There is not much large scale support tonight for convection. A
weak impulse aloft could be enough to trigger isolated to
scattered convection, especially with the surface boundary
moving into the area overnight. The boundary may slow down or
stall across the interior, which could remain as a focus into
the early morning hours for lingering showers or a storm,
especially across CT. The NAMnest is an outlier in the suite of
12z CAMS bringing the line all the way south across the coast
overnight. Have followed the consensus of the rest of the
guidance which keeps a PoPs below likely through night.
Warm and humid conditions are expected tonight with lows around
70 inland to the lower and middle 70s elsewhere.-- End Changed Discussion --
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
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The weak front will remain nearby on Friday. Uncertainty remains
on the timing and placement of convection since the models
indicate the front will be diffuse. The positioning of the front
will be important in determining convective development on
Friday. There is also a chance at some shortwave energy rounding
the base of a larger upper trough to the west in the afternoon
and evening.
Some of the guidance has hinted that a weak low will move out of
E PA in the morning and interact with the weak front over the
area. This scenario would develop convection in the morning
hours. The majority of the CAMs only hint at isolated to
possibly scattered activity in the morning. Have sided with the
CAMs with this forecast, but it is not out of the question that
convection is a bit more widespread in the morning. Think the
chance PoPs are good for now given the aforementioned
uncertainty. Convection is then likely in the afternoon and
evening. However, it is still a bit uncertain at just how
widespread it will end up being. Think there should be activity
that will grow in coverage in the afternoon from around the NYC
metro on NW and then shift east across the area later in the
afternoon and evening. However, if there is indeed more
development earlier in the day, the environment may end up more
stable with less in the latter portion of the afternoon and
evening.
Showers and thunderstorms may produce locally heavy rainfall and
minor flooding of poor drainage areas. Localized flash flooding
is also a threat. WPC has maintained the slight risk of
excessive rainfall on Friday for much of the area. SPC has also
maintained the marginal risk with an isolated threat of damaging
wind gusts. Have held off on issuance of a flood watch for
Friday based on the larger amount of uncertainty the usual for
this time frame, especially with the timing and placement of any
convection.
Convection should diminish in coverage later Friday evening with
weakening instability and loss of heating. Warm and muggy
conditions will continue Friday night.-- End Changed Discussion --
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
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A closed upper low over south central Canada will drift south
through Sunday and then evolve into an open trough Sunday night.
This trough then passes through the region Tuesday night into
Wednesday. Shortwaves will be rotating into the eastern portion of
the low as surface troughs/weak low pressures pass through the area.
There is a lot of uncertainty with the timing of the shortwaves,
and the development of the surface troughs/low pressures. Any of the
showers and thunderstorms may produce briefly heavy rain, especially
during Sunday as precipitable water values increase to 2 to 2.25
inches, and warm cloud processes dominate. And WPC continues to keep
most of the CWA in a slight risk for excessive rainfall, with the
potential for flash flooding. Monday the longwave upper trough will
be moving through the area and showers and thunderstorms will be
possible once again, and may be more diurnally driven.
Closely followed the NBM for temperatures and probabilities through
the extended period. Temperatures will be near seasonal normals
through the period, with no records expected to be broken.-- End Changed Discussion --
&&
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
A cold front approaches from the northwest this afternoon and
settles south across the area tonight. The front then lifts
north on Friday.
Forecast is mainly VFR through the TAF period outside of any
bouts of convection. Confidence in the timing and location of
showers and thunderstorms is too low at this time to include
with the exception of KSWF.
A line of showers and thunderstorms associated with a cold
front approaches from the northwest this evening and is likely
to dissipate before reaching the coastal terminals. However,
this will need to be closely monitored through this evening as
changes are quite possible. The front then stalls across the
area Friday morning. Guidance varies on how quickly the front
returns back to the north on Friday. Forecast does lean toward
this happening sooner than later.
A moderate southerly flow with gusts up to 25 kt at the coastal
terminals this afternoon before backing down this evening.
Winds will then go light and variable for a time during the
overnight as the front settles across the area. A return S/SW
flow around 10 kt develops by Friday afternoon from south to
north.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
A brief shower or thunderstorm is possible this afternoon and
then again late tonight. Low confidence of any shower or
thunderstorm activity in and around the NYC metro terminals
through Friday morning.
OUTLOOK FOR 18Z FRIDAY THROUGH MONDAY...
Friday Afternoon: Chance of MVFR or lower in showers/thunderstorms
in the afternoon.
Friday night: Chance of MVFR or lower in showers/thunderstorms,
mainly in the evening.
Saturday: MVFR or lower possible in the morning, otherwise VFR with
a chance of showers/thunderstorms in the afternoon and evening.
Sunday-Tuesday: Chance of showers/thunderstorms with MVFR or
lower.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
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A slightly stronger S-SE flow this evening may bring wind gusts
close to 25 kt on the near shore ocean waters west of Fire
Island Inlet. Otherwise, sub-SCA conditions are expected through
early next week. However, an increasing southerly swell Sunday
into Monday may allow for ocean seas to be near 5 feet at times
Monday into Monday night.-- End Changed Discussion --
&&
.HYDROLOGY...
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Locally heavy rain is possible from any shower or thunderstorm
through Friday night. The main concern is from minor poor
drainage flooding and a low potential of small stream from
reaching bankfull. The Weather Prediction Center has placed the
area in a slight risk for flash flooding Friday into Friday
night.
Additional rounds of moderate to locally heavy rain will be possible
Saturday and especially Sunday, with the threat of flash flooding,
nuisance, and minor flooding of poor drainage areas possible.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
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There is a moderate risk of rip current development at all the
ocean beaches this afternoon through Saturday.
Southerly winds with southerly swells around 2 ft will be in place
across the ocean beaches during this time period.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DS/MET
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...MET
AVIATION...DW
MARINE...DS/MET
HYDROLOGY...DS/MET
TIDES/COASTAL FLOODING...