okx-afd on 2024-07-13

642
FXUS61 KOKX 132105
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
505 PM EDT Sat Jul 13 2024

.SYNOPSIS...
A weak frontal boundary washes out offshore tonight. High
pressure returns Sunday with a thermal trough setting up over
the region Monday and Tuesday. A cold front then approaches from
the west on Wednesday, moving offshore Thursday. High pressure
builds in for the end of the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --Latest surface analysis reveals the weak frontal system
situated over the region. The boundary should work eastward into
the evening and then wash out offshore tonight. The clearing
conditions that have occurred have increased instability
somewhat, especially NW of the NYC metro. Have noted a few
showers developing well NW of our interior zones, but this
activity could slide southward early evening. Will continue to
highlight a slight chance PoP. Any isolated convection NW
quickly dissipates after sunset.

The other concern tonight will be with fog development due to
weak flow and lingering low level moisture. Confidence is not
high where fog will develop, but there appears to be a higher
probability across Long Island and southeast Connecticut. Left
mention of fog out of forecast over the NYC metro, but will also
include patchy fog for inland areas. The fog could become
locally dense near the coast if it does develop. Lows will range
from the upper 60s inland to the lower 70s near the coast.-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Heat Advisory remains in effect for portions of NE NJ, NYC
metro, and Nassau County beginning noon on Sunday.

A broad upper trough will persist over the region on Sunday.
Weak high pressure returns, but a thermal surface trough will
develop over the region by Sunday afternoon. The flow aloft will
also predominately be westerly, which should help dew points mix
out into the middle to upper 60s in the afternoon, especially
away from the coast. Models continue showing 850 mb temps mostly
17-19C during the afternoon, highest west of the NYC metro.
Afternoon sea breezes are likely to develop, so dew points near
coastal locations may not be able to have dew points mix out a
bit. There is a good consensus among the guidance for highs to
reach the upper 80s and lower 90s, warmest across NE NJ, NYC,
and interior Lower Hudson Valley and interior southwest CT. Heat
indices will peak at or just above 95 over the urban corridor
in NE NJ, NYC metro, and Nassau. It is possible that some
locations near the south coast fall just short of a 95 heat
index. Elsewhere, max heat indices should reach the upper 80s
and low 90s.

There may be some weak shortwave energy within the aforementioned
broad trough. However, model soundings indicate middle level
capping. This will prevent any substantial instability. The NBM
is showing a slight chance PoP west of the NYC metro, but feel
this may be overdone given the capping and weak instability.
Will keep PoPs below 15 percent west of NYC with this update.

Warm and muggy conditions continue Sunday night. Confidence in
any fog or low stratus is low at this time with westerly flow
increasing above the surface. Will keep sky conditions mostly
clear with lows generally in the 70s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Main points:

* Heat wave likely to continue through Wednesday with hot and
  humid conditions. Max heat indices forecast from the upper
  90s to low 100s. Potential for 105 urban and interior
  locations on Tuesday.

* Chances for showers and thunderstorms, mainly late afternoon
  into the evening for Monday and Tuesday. Best chance to the
  north and west of NYC. A more widespread chance of showers
  and thunderstorms exists for Wednesday into Wednesday night
  with a cold front.


Expect high heat and humidity during this time frame with the
forecast area residing at the southern edge of the westerlies.
Not only will very warm temperatures be advected into the
region in a deep-layered WSW flow, but less capping and
shortwave energy brings the potential for a late day/evening
MCS moving in from the west. This could further complicate the
temperature forecast with convective debris from upstream
convection.

As for temperatures, stayed close to the NBM, but there is the
potential for slightly higher values, especially since there is
not much spread in the box and whisker plots and the deterministic
forecast is generally below the 50th percentile. A target of
opportunity for this forecast will be the dew points, which
will be critical in how high heat indices get. In previous high
event this summer, there was more of a maritime influence, especially
for coastal locations. Deep mixing and more of a S/SW low-level
flow should help to transport some slightly lower dew point air
to the surface. Thus, to knock down the NBM dew points a bit,
used a blend of the CONSALL with the NBM. This keeps dew points
in the upper 60s to lower 70s during the times of max heating.
Regardless, heat indices will be in the upper 90s to lower
100s, possibly around 105 Tuesday across the urban corridor,
Lower Hudson Valley, and interior SW CT. Should higher dew
points be achieved, then the likelihood for Excessive Heat
criteria would increase. For the time, have held off on any
watches, but Heat Advisories are in effect Monday and Tuesday
for all but SE coastal CT and SE Suffolk on LI.

The best chance of convection looks to be on Wednesday/Wednesday
night as a cold front works across the area. There is some
uncertainty to the eastward progression of the front, and
chances linger into Thursday. Also, as previously mentioned,
MCS development at the southern end of the westerlies Monday and
Tuesday will need to be watched. High pressure then builds in
for the end of the week with temperatures closer to normal.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
A frontal boundary dissipates as it continues to slowly move
east going into tonight. High pressure returns for Sunday.

Mainly VFR going into this evening but there remains some
localized MVFR to sub-IFR, particularly at KISP, KHPN and KGON.
These terminals may just have a brief window of VFR this
evening.

The low stratus and fog will likely work its way west late
tonight into Sunday morning, which are forecast to bring MVFR
to IFR conditions. KSWF is also forecast to have some patchy fog
with MVFR overnight. KHPN and KBDR could also have some low
stratus and fog development and to a lesser chance for the NYC
terminals. Otherwise, VFR conditions are forecast for the rest
of the TAF period.

Winds overall will be southerly near 5 to 10 kts on average
for into this evening. Winds lower to near 5 kts tonight into
Sunday with wind direction becoming variable once again before
returning to a more SW flow on Sunday.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

SE winds could be 1-2 hours off at KEWR compared to TAF.

Southerly flow starting at KLGA this afternoon may be off by 1-2
hours.

A low chance of MVFR to IFR overnight into Sunday morning.

OUTLOOK FOR 18Z SUNDAY THROUGH WEDNESDAY...

Sunday: VFR.

Monday through Wednesday: Mainly VFR. A chance of afternoon into
early evening showers and thunderstorms with MVFR possible at
times. SW wind gusts 15-20 kt afternoon into early evening on
Tuesday and Wednesday.

Thursday: A chance of showers and thunderstorms with MVFR
possible.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90

&&

.MARINE...
Seas east of Moriches Inlet have subsided below 5 ft.
Therefore, the SCA has been cancelled. A relatively weak
pressure gradient tonight through Sunday night will lead to
conditions below SCA levels.

Winds and seas largely remain below SCA criteria through the
middle of next week. Ocean seas get to 5 ft Wednesday into
Thursday as southerly flow increases ahead of a cold front.

&&

.HYDROLOGY...
No hydrologic concerns are anticipated through the rest of the
weekend.

Given an abundantly moist air mass in place, any thunderstorms that
develop early to mid next week will have the potential to produce
locally heavy downpours that result in nuisance flooding,
particularly in urban and poor drainage areas.

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --A high rip current risk continues for all beach this evening,
and then through Sunday evening for the beaches of southeastern
Suffolk county. A southerly swell of 4 ft 7s will be slow to
subside into Monday. RCMOS and NWPS are generally in good
agreement with the high risk for the far eastern beaches. A
moderate risk can be expected elsewhere.-- End Changed Discussion --

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Heat Advisory from noon Monday to 10 PM EDT Tuesday for
     CTZ005>011.
NY...Heat Advisory from noon Monday to 10 PM EDT Tuesday for
     NYZ067>071-078>080.
     Heat Advisory from noon Sunday to 10 PM EDT Tuesday for
     NYZ072>075-176>179.
     High Risk for Rip Currents until 9 PM EDT this evening for NYZ075-
     080-178-179.
     High Risk for Rip Currents through Sunday evening for NYZ081.
NJ...Heat Advisory from noon Monday to 10 PM EDT Tuesday for NJZ002.
     Heat Advisory from noon Sunday to 10 PM EDT Tuesday for NJZ004-
     006-103>108.
MARINE...None.-- End Changed Discussion --

&&

$$

SYNOPSIS...DS/DW
NEAR TERM...DS/DW
SHORT TERM...DS
LONG TERM...DW
AVIATION...JM
MARINE...DS/DW
HYDROLOGY...DS/DW
TIDES/COASTAL FLOODING...