321
FXUS61 KOKX 051824
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
224 PM EDT Mon Aug 5 2024
.SYNOPSIS...
Weak high pressure this afternoon gives way to a slow-moving
cold front Tuesday which will eventually stall along or south of
our area into Wednesday. The frontal boundary may briefly sag
further south on Thursday before lifting back into the area for
the end of the week. There is uncertainty with the future track
of Tropical Cyclone Debby and how it may interact with the
boundary. Please refer to the latest official forecast from the
National Hurricane Center.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
The forecast remains on mainly on track with minor adjustments
made to some of the hourly forecast elements.
Plenty of sunshine this afternoon with highs in the low-90s to
upper-80s. Dewpoints will be low enough to have heat indices
mostly in the same range.
For this evening we will have increasing PWATs in the
afternoon and evening up to 1.6-1.7", and decent SBCAPE ranging
1000-2,500 J/kg. However, with no major source of lift,
expected only the slight chance for a few showers/thunderstorms.
CAMs are showing the chance for 40-45 kt 06km shear north, west
and around NYC which means any storms that are able to develop
should have some organization to them. SPC currently has far
northern portions of the Lower Hudson Valley under a Marginal
risk of severe weather, and this has trended down slightly from
previous outlooks.
Expecting mostly cloudy skies to take over tonight with a cold front
continuing to approach closer to our CWA. A few showers and
thunderstorms are possible as the front nears with PWATs increasing,
mainly for northern portions of the CWA.-- End Changed Discussion --
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
A slow-moving cold front with pass over the area on Tuesday and is
expected to stall over the area or south of the area. There is
some uncertainty with regards to where the front stalls since it
mainly hinges on high pressure in Canada and how far south it
nudges the front. This has lead to different solutions among the
CAMs and could greatly influence how much rain we see.
Speaking of rain, this Tuesday to Wednesday timeframe could end up
being a very wet period for us. As the front passes over the region
and begins to stall, enhance tropical moisture feeds along the
boundary, increasing PWAT values Tuesday. PWATs look to peak along a
West to east axis in line with the front Tuesday evening into
Wednesday afternoon. Along the front, 00Z guidance varies, bringing
maximum PWATs anywhere from 2.3 to 2.7 inches. Given the max moving
average PWATs from SPC`s Sounding Climatology page are 2.14", the
2.7" values seem somewhat unrealistic (seen in CAMs like NAM NEST
and HRRR). Regardless, it signals that this cold front could bring
the risk for heavy rainfall. Model soundings also show a decent-
sized warm cloud layer and ideal tall-skinny CAPE profiles for
efficient rainfall. The question remains, however, where the front
stalls. We`ll likely see a period of heavy rainfall Tuesday evening
into Tuesday night as the front passes, but where it stalls on
Wednesday will signal the area at greatest risk for flash flooding.
For now, the models are split. Some guidance shows the front and
axis of highest moisture along Long Island, NYC and NE NJ while
other guidance has higher pressure to our north nudging a little
farther south, leading to the front stalling just south of our area.
WPC currently has us in a Slight Risk for Excessive Rainfall fro
Tuesday. This forecast will become better resolved once more
guidance agrees on the location of the stalled front and all the
CAMs are able to resolve the full event. Either way, showers and
thunderstorms on Tuesday evening and Tuesday night are expected to
have the potential for heavy rainfall which could lead to instances
of flash flooding.
If the front stalls in our area on Wednesday, heavy rainfall may
continue throughout much of the day before tapering off Wednesday
night. However, if the front stalls to our south, we`ll likely only
see scattered showers. Thunderstorms look less likely on Wednesday
due to weak forcing and very little instability.
Wednesday night high pressure to our north is expected to nudge in
further, which should lead to any lingering rain, clearing, with
only isolated showers leftover under partly cloudy skies.
Temperatures during this period will be cooler aided by the rain,
cloud cover, and somewhat lower heights aloft. Highs on Tuesday will
be in the mid-70s to mid-80s. Highs drop into the mid/low-70s on
Wednesday.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
This is a highly complex forecast with much uncertainly due to the
potential interaction of a frontal boundary with tropical moisture
associated with tropical cyclone Debby. In addition, the future
track of Debby will play a big part in how this portion of the
forecast unfolds. Refer to the latest official forecast from the
National Hurricane Center.
The 00Z GFS is an outlier with the future track of Debby once we get
from approximately Wednesday and beyond. A relatively weak shortwave
trough passing to the north during the midweek period provides
enough of a weakness to draw the low slowly north and then northeast
by the weekend, with a track just south and east of the forecast
area. The GFS on the contrary is just far enough south with the
surface low to miss the weakness and retrogrades the low west along
the Gulf Coast states. The GEFS shows quite a bit of spread with its
members, encompassing an area all the way from the eastern Gulf to
the Northeast by the weekend. Bottom line, there are small details
here that can have significant impacts on the forecast. Thus, with
all the uncertainty any deviation from the NBM was subtle.
As this time, the best chance of rain looks to be late Thursday into
Friday with the potential for a significant rainfall event for the
forecast area as tropical moisture overruns a mid latitude frontal
system. Now even with the GFS this becomes more apparent as a
stronger upper trough sends a cold front toward the region for the
weekend, strengthening the frontal zone as the offshore coastal
front returns north as warm front. So the potential for heavy
rainfall arises in both scenarios. There is also quite a bit
difference with the magnitude of the upper trough and cold front for
the weekend.
Daytime highs Thursday and Friday are actually forecast to be
several degrees below normal due to the forecast cloud cover,
chances of rain, and an easterly flow (north of the offshore front).
Temperatures rebound a bit over the weekend as rain chances
decrease, especially for the second half of the weekend.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
Weak high pressure gives way to a slowly approaching cold front.
The front passes through the area late tonight into Tuesday
morning, but stalls close to the area.
Mainly a VFR forecast. MVFR will be possible for most terminals
starting towards noontime Tuesday as showers become more likely.
Can`t completely rule out thunder, but will leave the mention
out of the TAFs for now.
SE to SW sea breezes at around 10kt for most terminals. Winds
bcmg lighter and veering W overnight. Wind shift NE then E to SE
during Tuesday, increasing back to around 10kt.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Winds might vary SW to SE at KTEB this afternoon.
OUTLOOK FOR 18Z TUESDAY THROUGH FRIDAY...
Tuesday PM...Mainly VFR. SHRA with iso TSTM possible.
Tuesday Night-Wednesday: MVFR to IFR in SHRA.
Thursday: Chance of MVFR or lower in SHRA.
Friday: MVFR/IFR in SHRA. SE gust 20-25kt possible.
Saturday: MVFR/IFR in RA/SHRA. E to NE gusts around 25kt
possible.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Sub-SCA conditions are expected for the remainder of today and
into Tuesday, and through Wednesday night.
There is quite a bit of uncertainty for the end of the week due to
the future track of tropical cyclone Debby. Long period southerly
swells may start arriving Thursday into Friday, but at this time
seas are kept right around 4 ft. However, this could significantly
change. Refer to latest forecast information from the NHC.
&&
.HYDROLOGY...
There is the potential for heavy rainfall Tuesday into Wednesday as
a weak area of low pressure moves along a stalled frontal boundary
in the vicinity of the forecast area. However, there remains a good
deal of uncertainty in exactly where the axis of heavy rain will set
up. There will be potential for flash flooding considering the
tropical airmass but too much uncertainty to give precise locations
of higher rainfall amounts. For now, Tuesday afternoon into
Wednesday about 1-2 inches of rain is expected with localized higher
totals possible. WPC has our entire area in a slight risk for
excessive rainfall Tuesday into Wednesday morning.
Another round of heavy rainfall is possible late Thursday into
Saturday as a frontal system potentially interacts with tropical
moisture associated with tropical cyclone Debby. There is even more
uncertainty with this feature.
&&
.TIDES/COASTAL FLOODING...
A high risk of rip currents is expected to continue through at least
Tuesday evening, likely into Tuesday. This is due to southerly
swells of around 4-5 feet.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...High Risk for Rip Currents through Tuesday evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...None.-- End Changed Discussion --
&&
$$
SYNOPSIS...BR/DW
NEAR TERM...JE/BR
SHORT TERM...BR
LONG TERM...DW
AVIATION...JC
MARINE...BR/DW
HYDROLOGY...BR/DW
TIDES/COASTAL FLOODING...