013
FXUS61 KOKX 072155
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
555 PM EDT Wed Aug 7 2024
.SYNOPSIS...
A stationary front will remain across the Middle Atlantic
through Thursday before retreating north towards the area
Thursday night into Friday morning. Post-tropical cyclone Debby
passes well west of the area Friday night as it interacts with
an approaching frontal system. The associated cold front will
likely pass through the area Friday night into early Saturday
morning. Broad low pressure then remains north of the area, with
a few surface troughs/weak cold frontal passages early next
week.
Please refer to the latest official forecast on Debby from the
National Hurricane Center.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
The forecast has been updated mainly to bump up PoPs slightly
heading into this evening as per latest guidance and radar
trends.
The cold front that moved through Tuesday night remains
stationary across the Middle Atlantic to well south of Long
Island. High pressure over New England continues to build
southward with the two systems combining to bring a E-NE flow to
the area. The surface ridging and some drier air has brought an
end to the light showers across CT, but scattered light showers
linger across NE NJ, NYC metro and Long Island. The surface
ridging and slightly drier air help taper the showers off from
east to west through this evening. Generally higher PoPs across
portions of NE NJ and adjacent areas, which are furthest west
from the stronger surface ridging.
Mostly dry conditions are expected thereafter until late
tonight when warm advection increases along with some subtle
shortwave energy shifting northward around the building
subtropical ridge offshore. PoPs begin to increase, especially
near the coast, towards daybreak Thursday. Any showers that
develop near the coast should remain on the lighter to locally
moderate side since there the environment is stable north of the
front.
Lows will range from the lower 60s inland to the middle and upper
60s elsewhere, near to slightly below normal for this time of
year.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Tropical cyclone Debby will continue to slowly move across the
Carolinas on Thursday before slowly lifting towards the middle
atlantic Thursday night. Please refer to the National Hurricane
Center for the latest forecast information.
The main forecast challenge for Thursday will be how much
lingering surface ridging impacts potential shower activity
associated with warm advection/overrunning. There is support
aloft from a departing jet streak off the New England coast. The
latest model guidance has started to come into better agreement
that overrunning showers will overspread the area from
southwest to northeast during the morning/early afternoon hours.
This activity may struggle to make it north and east due to the
lingering ridging and proximity of the surface high, so highest
PoPs are confined to the coast, NYC metro and NE NJ. The
atmosphere remains stable which will prevent thunderstorms from
developing, but there could be some locally moderate showers.
Overall not anticipating any heavy rain threat from the round of
showers during the morning/early afternoon. The favorable jet
position pushes east in the afternoon, but overrunning likely
continues. Not confident enough to go likely PoPs with little
larger scale support, but scattered showers cannot be ruled out
into the evening.
The high pressure begins shifting off the New England coast
Thursday afternoon into Thursday night. However, there is still
no organized synoptic scale forcing mechanism for organized
showers. Model consensus is indicating rising PoPs from west to
east Thursday night, which is likely from enhanced overrunning
from the front to the south lifting northward. The front may
ultimately be located near or over the region by day break
Friday morning. Will generally follow the trend with the model
consensus, but slow down the timing of the increasing PoPs until
late Thursday night when the front should be closer to the
area. Forecast soundings indicate some destabilization aloft,
but have kept mention of thunder out of the forecast through
early Friday morning. A few locally heavy downpours cannot be
ruled out given the high amount of moisture, but no widespread
heavy rain is anticipated Thursday night.
Another day of below normal temperatures is likely for
Thursday. It should be a bit warmer compared to Wednesday, but
temperatures may struggle to rise much above the low 70s with
clouds, E flow, and showers around the region.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Debby continues to weaken on Friday, heading north through
the mid-Atlantic and central PA. At the same time, a cold front
in association with a low pressure center near the northern
Great Lakes will push in from the west. A warm front forms from
the combination of the two systems, and is expected to be over
or near the forecast area at the start of the day, then heads
north through the rest of the day. Rain is likely, but regarding
heavier downpours, the timing would be more focused during
Friday night into Saturday morning as PWATS increase 2.25 to
2.50 inches and stronger forcing from the approaching cold front
and strengthening low level jet come into play. Isolated to
scattered instances of flash flooding will be possible Friday
into Saturday morning as soils will be saturated from antecedent
rainfall. Mitigating the flooding threat somewhat will be the
relatively quick forward motion of the of storm cells as the
steering current strengthens. These increasing winds aloft will
however add to the threat of supercells as winds veer with
altitude, increasing the directional shear. The greater threat
for severe thunderstorms, and potentially even an isolated
tornado, would more likely be Friday afternoon and night when
instability will be greater, but both are still not out of the
question Friday morning. It should be a breezy day regardless as
the pressure gradient tightens in response to Debby`s center
passing to our west while tracking northward. Gusts of 30-35mph
will be possible, especially for coastal areas. Even outside of
thunderstorms, there`s the potential for even stronger gusts
(40mph+) Friday night as downpours may help transport winds
downward from a 55-60kt 925mb llj.
The cold front exits east of the area sometime Saturday morning,
with dry conditions expected by the afternoon. A closed 500mb low
in the vicinity of the northern Great Lakes then slowly shifts
east as it opens up through Tuesday, keeping a cyclonic flow
aloft over the forecast area through the period. A series of
weak troughs may therefore pass through, however moisture is
fairly limited, so will go with a dry forecast. The flow aloft
may flatten a little on Wednesday, but still cyclonic as per
global models. Will continue with a dry forecast. Highs Saturday
through Wednesday mostly 80-85, and after dewpoints lower
Saturday afternoon, expect dewpoints generally around 60 for the
rest of the forecast period.
&&
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
The stalled front will remain south of the area through Thursday,
then push northward Thursday night into Friday.
Predominantly IFR/MVFR conditions across the area terminals
through this evening with some spotty showers, mainly near the
coast. Slow improvement to VFR starting from the north in the late
afternoon and reaching the NYC terminals late this evening is
possible, with NYC terminals possibly bouncing in and out of
VFR/MVFR. Cigs then lower back down to MVFR/IFR for Thursday
everywhere, along with lowering vsbys as the front begins to move
back north triggering showers across the area.
Winds will be out of the E/NE through the TAF period at 10-15 knots.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments likely through the afternoon/evening as cigs
improve.
Potential for NYC terminals to stay MVFR and not improve to VFR
this evening.
OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday: MVFR or lower in SHRA.
Friday through Saturday morning: MVFR/IFR in SHRA. SE gust
25-30kt possible. LLWS possible late Friday and into Friday night.
Saturday Afternoon through Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
As Post Tropical Cyclone Debby passes to our west, SCA
conditions are likely on all area waters starting Friday, and
lasting into Saturday morning on the non-ocean waters. On the
ocean, SCA conds will continue through at least part of Saturday
night as seas will be slow to subside due to a lingering swell.
Waves here may build 7 to 12 ft during Friday night. Can`t rule
out gales on all waters starting late in the day Friday, but
more likely to occur Friday night. Sub-advisory conditions
anticipated for most of Sunday through the rest of the forecast
period.
&&
.HYDROLOGY...
No hydrologic impacts are anticipated through Thursday night.
Isolated to scattered flash flooding will be possible Friday
into Saturday morning, with the overall more likely period for
impacts being late Friday afternoon through Friday night.
Rainfall rates of mostly 1-2 inches per hour will be possible
during this time. Both river/stream flooding and urban/poor
drainage flooding will be possible given antecedent
rains/saturated grounds. The overall higher chances for flooding
will be across NE NJ, NYC, and the Lower Hudson Valley into
western CT where WPC maintains a slight risk of flash flooding.
&&
.TIDES/COASTAL FLOODING...
A moderate risk for rip current development is expected on
Thursday, increasing to a high risk on Friday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...High Risk for Rip Currents from Friday morning through Friday
evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ350-
353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JC/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...JC
AVIATION...20
MARINE...DS
HYDROLOGY...DS
TIDES/COASTAL FLOODING...