124
FXUS61 KOKX 290557
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
157 AM EDT Mon Jul 29 2024
.SYNOPSIS...
High pressure gives way to a surface low offshore over southern
New England tonight through Monday. The low heads northeast as
a series of disturbances move through the area midweek. A weak
frontal system approaches at the end of the week into the
weekend.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --
Forecast updated to reflect current observations.
Widespread rain has moved into much of southern Connecticut and
is gradually spreading west toward the NYC metro and the Lower
Hudson Valley. Showers will likely continue to overspread much
of the area through morning with gradual dissipation of shower
activity after sunrise. While not likely, there is a chance of
isolated embedded thunder.
With cloud cover and showers around overnight, low temperatures will
be a few degrees warmer than Saturday night, in mid to upper 60s and
low 70s across the board.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
The surface low continues moving north of the area on Monday
weakening/dissipating as it moves inland over southern New England.
With the upper low remaining nearly overhead, or just to the north
on Monday, precip chances remain, especially in the afternoon.
Increasing instability with the cold pool aloft will steepen lapse
rates by Monday afternoon, with increasing potential for isolated to
scattered thunderstorms through Monday evening. Model soundings
depict modest instability (>1000 J/kg SB CAPE) and some shear (>25-
30 kts max) though there is a question of coverage and a distinct
convective initiation mechanism. So, thunderstorm occurrence is
quite conditional on initiation Monday afternoon and the 12Z CAMs do
depict activity in and around NYC and points north and west after
18Z.
The upper low begins to pull away on Monday night with another mid
level shortwave on its heels. As it approaches, the trough may
instigate another round of afternoon showers and thunderstorms
Tuesday afternoon, particularly north and west of NYC. The day will
be dry for most, however, with just chance to slight chance PoPs
across the forecast area.
Predominately southerly flow will also strengthen a bit on Tuesday
which will advect more humid air in to the area. Highs will be in
the low to mid 80s with heat indices just a few degrees higher.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Points:
* Multiple rounds of showers and thunderstorms mid week into the
weekend.
* Increasing heat and humidity will increase chances for heat
indices approaching and/or exceeding 95F for the end of the
week.
Westerlies look to be active this period and will send multiple
shortwave troughs across the forecast area during this time. What
has changed in the last 24h is the timing of these features, in
particular the first one, which has sped up a bit. This will
result in a good chance of showers and thunderstorms Tuesday
night into Wednesday. PWATs around 2 inches will also result in
the potential for locally heavy rainfall. However, the thermal
boundary associated with the system is relatively week or non-
existent. While the instability is marginal to moderate, deep-
layered shear is weak. So any severe or flash flood threat at
this time looks to be isolated. Still though, it is a bit early
to be specific with details. This should be better resolved
once we get into the time window of the CAMs.
Shortwave ridging behind the first system should help to dry
out conditions for the Thursday and Friday, albeit there still
will be a chance of diurnally driven convection, but mainly
north and west of NYC. Another upper level trough will send a
weak frontal system into the area Friday night into Saturday
with increasing chances of convection. There are significant
timing issues with this system as should be expected this far
out. The 12Z operational ECMWF is less progressive with this
feature versus the operational GFS and Canadian.
In addition, it will become increasingly hot and humid for the
second half of the week, featuring highs in the mid 80s to the
lower 90s with dew points around 70 or higher. This results in
heat indices 95 or higher for a good portion of the area. The
high humidity will be courtesy of a prolonged period of southerly
flow. This will also keep overnight lows several degrees above
normal. To note, NBM box and whisker plots during this time do
point to the potential for higher temps with the 50th percentile
generally higher than the deterministic run. However, stuck
with the NBM at this juncture in time.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
Weak low pressure tracks along the New England coast overnight
into Monday morning, then dissipates over northern New England
Monday afternoon. Another weak low, or trough of low pressure
remains to the west of the area into Monday night.
Generally VFR, with IFR at KGON, with showers, brief MVFR is
possible with the showers. An isolated thunderstorm is possible
across southeastern Connecticut through 09Z. Showers taper off,
becoming more scattered by late Monday morning. By late
afternoon into the early evening there is a chance of
thunderstorms at the NYC metro terminals.
A light southerly flow will prevail through the forecast
period. Winds overnight at the outlying terminals are light and
variable.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments are possible for timing of showers, and low potential
for MVFR conditions. There is the possibility of an isolated
thunderstorm overnight.
OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
Late Monday Night: Mainly VFR. A chance of MVFR to IFR in -SHRA
and stratus.
Tuesday and Wednesday: Scattered to numerous aft/eve showers
and thunderstorms. S winds G25kt possible for coastal terminals.
MVFR/IFR stratus potential, particularly for coastal terminals
and overnight/AM.
Thursday and Friday: VFR Chance of MVFR in afternoon
showers/thunderstorms. SW winds.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Winds and seas remain below SCA levels across the forecast waters
today through Monday night. However, with an offshore low pressure
approaching the southern New England coast tonight into early
Monday, ocean seas east of Fire Island Inlet may approach 5 feet by
midday Monday into Monday evening. Given the low confidence and
occasional nature, have elected to hold off on any SCA issuance at
this time.
Sub SCA conditions likely for mid to late week with a weak pressure
gradient.
&&
.HYDROLOGY...
There is chance of nuisance flooding overnight across southern CT
with low end probabilities of >1" per hour rainfall rates and slow
storm movement overnight. In collaboration with WFO BOX and WPC, we
have introduced a small MRGL risk of excessive rainfall for southern
CT through early Monday.
Thereafter, multiple rounds of showers and thunderstorms are
possible Tuesday into Wednesday and again heading into the
weekend. However, it is too early to be specific with hydrologic
impacts.
&&
.TIDES/COASTAL FLOODING...
A strengthening southerly flow Monday and Tuesday in
conjunction will a building swell will produce a moderate rip
current risk at the ocean beaches. There is even the potential
for a high risk on Tuesday as the swells take on a more
southerly approach to the shore increasing the amplitude of
waves in the surf zone.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DBR/DW
NEAR TERM...DBR/MW
SHORT TERM...DBR
LONG TERM...DW
AVIATION...MET
MARINE...DBR/DW
HYDROLOGY...DBR/DW
TIDES/COASTAL FLOODING...