743
FXUS61 KOKX 260017
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
817 PM EDT Sun Aug 25 2024
.SYNOPSIS...
-- Changed Discussion --
High pressure continues to shift offshore this evening into
Monday. A surface trough then develops tonight into Monday
across the area weakening and dissipating. High pressure then
builds north of the region on Tuesday. A warm front moves
through Wednesday, followed by a cold front Wednesday night.
High pressure returns Thursday into Friday. A warm front
approaches to begin the weekend, with a cold front likely to
follow later in the weekend.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
Some showers and a few t-storms have persisted into the mid
evening. Any storms have not been able to achieve severe levels,
with a couple of stronger storms getting somewhat close up to
the north and northwest, but ultimately have gradually weakened.
Some lightning strikes are possible through the evening, with
just a few lingering showers ultimately diving SE across the
eastern Hudson Valley and interior So. CT. Eventually the
activity completely dies off with just some leftover clouds at
times from the previous convection. Skies ultimately become
mostly clear later in the overnight. Have added some patchy fog
in the hourly forecast database late in the night with some
areas up north having a wet ground, thus some fog appears more
likely now for the northern interior valley locations.
Lows tonight look similar to last night with upper 50s across the
interior and low to mid 60s elsewhere under SW flow at the
surface.-- End Changed Discussion --
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Attention on Monday turns to the severe weather potential,
which has increased across the eastern portion of our area.
The upper low out of Quebec continues to head south through the day
on Monday. Height falls will result as the cold pool becomes more
centered over New England by Monday afternoon. The upper low weakens
as it heads southeast and opens up as a trough by Monday evening
into the overnight. At the surface, a trough develops during the
afternoon as the upper trough approaches. These features will set
the stage for initiation of afternoon showers and thunderstorms, some
of which will be strong to severe, especially for eastern Long
Island and southeast CT on Monday afternoon and evening.
Current convective allowing models show modest instability building
by Monday afternoon along with some bulk shear for organized storms
as the cold pool aloft approaches. The timing of cells moving
south/southeast from southern MA/northern CT along the western
periphery of the upper low varies from about 17-18Z to as late as 20-
21Z. The 12Z HREF mean MUCAPE shows about 1500-2000 J/kg maximized
over southern CT with bulk 0-6km shear values approaching 40 kts.
Model soundings from individual HREF members also show some good
CAPE in the hail growth zone along with a fair amount of DCAPE (500-
1000J/kg), suggesting that severe hail and wind gusts are the main
hazards. In fact, SPC has upgraded portions southern CT and eastern
LI to a slight risk of severe thunderstorms (2 out of 5), with 15%
probabilities of severe winds and large hail. Finally, with modeled
PWATS of less than 2", flash flooding is not a major concern with
this event at this time; see the hydro section below for more
details.
Convection should weaken by early evening as the low/upper trough
pulls away to the northeast. Drier conditions then return late
Monday into Tuesday as upper ridging builds in from the
southwest.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Weak high pressure will keep things quiet and dry Tuesday
night. On Wednesday a warm front approaches and is progged to
move through. How quickly this happens will determine how
quickly any clouds ahead of the warm front dissipate and move
out. This ultimately will determine how hot things get as a
humid air mass will be in place, especially immediately behind
the warm frontal passage. Heat indices should manage to get into
the 90s for a majority of the area, with dew point readings
mainly around 70. If complete sun breaks out early enough then
heat indices should reach 95 to 100 for the western half of the
area, with some lower 100s possible in urban NE NJ. With the
warm front expect some showers, and possibly a few
thunderstorms. More activity is then possible later in the day
and towards evening just ahead of a cold front. See hydro
section regarding rain and QPF details.
There had been some disagreement among the NWP global guidance in
previous cycles, but now there appears to be more agreement that the
front behaves progressive enough as to get off the coast and clear
the area by Thursday morning. In its wake expect clearing skies and
high pressure to build for the remainder of Thursday into Thursday
night with some lowering of the humidity. Another frontal system
then approaches Friday night, with another round of showers possible
into Saturday with currently chance to slight chance PoPs. At this
time much of Sunday will likely be dry, although a secondary cold
front may approach which could bring a few showers. For now have
opted for chance to slight chance showers with timing highly
uncertain this far out.
After hot and quite humid conditions for Wednesday, temperatures
overall are expected to average near normal thereafter through the
remainder of the long term.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
High pressure centered off the Mid Atlantic coast will continue
to slowly work south and east and away from the area. At the
same time, low pressure will drop south across northern New
England and into the area on Monday.
VFR with SCT CU through tonight, likely becoming BKN on Monday.
An isolated SHRA/TSRA is possible this evening with the best
chance north and west of the NYC terminals. For Monday, chances
increase for the eastern terminals, especially late morning into
the afternoon. Will include a TEMPO at KGON, PROB30s at KISP and
KBDR, and for now leave out of the remainder of the TAFs. If
confidence increases, there is a chance that as thunder may
need to be added to the NYC/KHPN terminals.
Winds become light S/SW to variable tonight, then light W/SW
for the Monday morning push. Winds will become more southerly at
the coastal terminals around 10 kt in the afternoon. For the
Lower Hudson Valley terminals, KEWR, and KTEB, winds may vary
from W to NW at less than 10 kt. This will depend on the
location of a surface trough on Monday.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Thunder may be possible at the NYC terminals on Monday
afternoon/evening. Confidence too low to include in the TAFs.
Higher confidence east of NYC.
OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
Monday night: Chance of IFR in stratus/fog, especially east of
NYC.
Tuesday: VFR.
Wednesday: Chance of MVFR or lower in aft/eve SHRA/TSRA.
Thursday-Friday: Mainly VFR. Chance of aft/eve SHRA/TSRA,
mainly north and west of the NYC terminals.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Winds and seas are expected to remain below SCA criteria
through Tuesday, as the pressure gradient remains weak across
the region.
Sub small craft conditions prevail into the middle of the week with
ocean seas likely not getting above 3 ft through Wednesday.
Marginal small craft seas then become possible late Thursday
and Thursday night for eastern portions of the ocean.
&&
.HYDROLOGY...
There is chance of nuisance flooding with perhaps an isolated
flash flood threat across southeastern CT and extreme eastern
Long Island Monday afternoon and evening with any thunderstorm
activity. Flash flood guidance from NERFC depicts around 2-2.25"
in an hour or 2- 2.5" in three hours with respect to antecedent
conditions across these areas. With progged PWATS less than 2"
and a somewhat progressive steering flow for storm movement,
widespread flash flooding is not anticipated.
The UFVS-trained model is suggestive of a marginal risk of excessive
rainfall for Wednesday, and this lines up well with WPC`s marginal
risk. At this time the flow appears that it would be progressive
enough to preclude significant or meaningful hydro impacts. However,
minor hydrologic impacts more related to nuisance or minor
urban related flooding cannot be ruled out Wednesday. Rainfall
amounts across northern portions of the area could average close
to an inch, with locally higher amounts possible in association
with any thunderstorms.
&&
.TIDES/COASTAL FLOODING...
There will be a low rip current risk for the ocean beaches Monday.
The low risk is expected to prevail with the primary wave packet
being under 5-6 seconds. The low risk continues overall into Tuesday
with the exception of a moderate rip current risk for the eastern
Suffolk ocean beaches Tuesday afternoon. Surf heights will generally
be 1 to 2 ft. The risk should increase into Wednesday with more of a
southerly wind wave.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JE/DBR
NEAR TERM...JE/DBR
SHORT TERM...DBR
LONG TERM...JE
AVIATION...BC
MARINE...JE/DBR
HYDROLOGY...JE/DBR
TIDES/COASTAL FLOODING...