189
FXUS61 KOKX 071813
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
213 PM EDT Wed Aug 7 2024
.SYNOPSIS...
A nearly stationary front will remain near the coast through
Thursday. The front will then return northward Thursday night
into Friday. Post-tropical cyclone Debby passes well west of
the waters Friday night as it interacts with an approaching
frontal system. The associated cold front will likely pass
through the area Saturday morning. Broad low pressure then
remains north of the area, with a few surface troughs/weak cold
frontal passages through early next week.
Please refer to the latest official forecast on Debby from the
National Hurricane Center.
&&
.NEAR TERM /THROUGH TONIGHT/...
Forecast mainly on track. Much cooler air mass has worked into the
region with the stationary front just south the of the area.
High pressure builds down from the north into tonight, which
will only reinforce some of the lower level cooler and drier
air.
There could some spotty showers this afternoon, mainly near the
coast. No heavy rain is anticipated. There is some uncertainty
whether the spotty showers will continue this evening,
especially with surface ridging trying to take hold from high
pressure to the north. Additionally, sufficient low and mid
level moisture will keep conditions mostly cloudy. Some partial
clearing is possible across the Lower Hudson Valley and CT late
this afternoon into this evening.
An NE flow (gusty up to 20 mpg at the coast), cloud cover, and
weak cold advection will result in highs in the upper 60s and
lower 70s, which is about 10 degrees below normal. However, the
reverse can be expected tonight with lows in the 60, which is
close to normal.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Guidance has come into better agreement with post-tropical
cyclone Debby taking a more inland track up the spine of the
Appalachians during this time frame. A strengthening subtrop
ridge across the western Atlantic and an amplifying trough
dropping across the upper Midwest into the Great Lakes will draw
the system northward. The latter of which will also send a
strong cold front toward the region. Warm advection and a
strengthening southerly flow will send tropical moisture
northward along with the stalled front over the Mid Atlantic
states. This will result in gradually increasing rain chances
Thursday into Friday, with the best chance for moderate to
possible heavy rainfall not until late Thursday night into
Friday. However, due to a weaker low, more westward track, and
the system speeding up, rainfall amounts are trending lower. The
Day 3 Excessive rainfall outlook from WPC now has the area from
NYC east in a marginal risk, and areas to the west under a
slight risk. This from 12Z (8 AM) Friday to 12Z (8AM) Saturday.
During this time, 2 to 3 inches is expected across the slight
risk area, with 1 to 2 inches across the marginal risk area.
Isolated to scattered instances of flash flooding will be possible
as the tropical moisture interacts with multiple boundaries.
This coupled with the recent heavy rainfall across the area and
increased streamflow on area rivers and streams could lead to a
quicker response and increased flood threat. This will need to
be closely watched in coming days.
In addition, there is marginal risk for severe weather for
Friday due to enhanced wind shear as Debby passes to the south
increasing the low-level southerly flow. Isolated tornadoes are
possible.
Southerly winds to the east of the low track will increase on
Friday with gust up to 35 mph possible across the Atlantic
facing shoreline. Temperatures warm during this time, getting
closer to around 80 for highs on Friday with high humidity as
dew points get into the 70s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Key Points:
*Post Tropical Cyclone Debby will likely pass just west of the area
Friday night as it interacts with an approaching frontal system. The
heaviest axis of rainfall continues to shift west of the area.
However, the potential for isolated to scattered flash flooding
remains. Please refer to the latest official forecast on Debby from
the National Hurricane Center.
*A dry period with slightly below normal temperatures is expected
Sunday through early next week.
As Post Tropical Cyclone Debby approaches from the south it will
interact with an approaching frontal system from the west. Strong,
deep lift combined with pwats between 2.25 and 2.50 inches will
bring a period of moderate to heavy rain that will likely be ongoing
at the start of the Friday night period and will continue into
Saturday morning. The latest 00z guidance continues the westward
trend of the axis of heaviest rainfall. See the hydrology section
below. Along with the rainfall, some gusty winds are expected.
Southerly winds of 20 to 25 mph could gust up to 30 to 35 mph. These
values are mainly for Long Island and coastal areas.
The cold front passes through our area sometime Saturday morning,
with dry conditions expected through early next week. Broad low
pressure lingers to our northeast at the surface, while an upper
level trough remains over the eastern US. A few surface troughs/weak
cold fronts will rotate through the area. This pattern will result
in slightly below normal temperatures for early August, with highs
in the upper 70s to low 80s.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
The stalled front slowly starts moving south of the area today.
Predominantly IFR/MVFR conditions across the area terminals
through this evening with some spotty showers, mainly near the
coast. There is the potential for slow improvement to VFR
starting from the north in the late afternoon and reaching the
NYC terminals late this evening, 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 due
to -SHRA.
Winds will be out of the E/NE through the TAF period, increasing
to 10-15 knots today.
...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.
Saturday Afternoon through Monday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
NE winds across the waters will continue bringing a period of
marginal SCA conditions to the ocean this afternoon and early
evening. A SCA remains in effect for the ocean waters through
the first half of tonight. Otherwise, east winds could gusts up
to 20 kt on all waters into Thursday. Winds then become
southerly on Friday as post-tropical cyclone Debby tracks well
west of the waters. Marginal gales are possible on the ocean
waters.
As Post Tropical Cyclone Debby passes to our west, SCA conditions
are likely. 25 to 30 kt gusts are possible Friday night through
Saturday morning, along with 8 to 10 ft seas. Gusts fall below
25 kt by Saturday afternoon, but seas remain elevated through
potentially Sunday. Sub- SCA conditions are expected thereafter.
&&
.HYDROLOGY...
Another round of heavy rainfall is possible late Thursday night
into Saturday morning as Post Tropical Cyclone Debby passes to
our west. The heaviest axis of rainfall continues to shift west,
with the highest expected totals now west of the area. The new
Day 3 from WPC keeps the moderate risk just west of Orange
County and pulls the slight risk`s eastern extent in from
central CT to western Long Island. Areas east of this line are
now in a marginal. Average forecast QPF totals are 1 to 3
inches, with the higher end of this range across the Lower
Hudson Valley. Uncertainty still remains and the axis could
still shift. It is too early to talk specific rainfall rates,
but isolated to scattered flash flooding remains a possibility
for the entire area.
&&
.TIDES/COASTAL FLOODING...
A moderate risk is forecast for today and Thursday as southerly
swells start to diminish late tonight.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ350-
353-355.
&&
$$
SYNOPSIS...JT/DW
NEAR TERM...DS/DW
SHORT TERM...DW
LONG TERM...JT
AVIATION...20
MARINE...JT/DW
HYDROLOGY...JT/DW
TIDES/COASTAL FLOODING...