discussion on 2023-06-26

000
FXUS61 KOKX 261318
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
918 AM EDT Mon Jun 26 2023

.SYNOPSIS...
A pre-frontal trough approaches today and will move across the
area this evening into tonight. A slow moving frontal system
will then impact the area Tuesday into the late week. Weak high
pressure tries to move in Friday before another frontal system
approaches from the west impacting the region through the
weekend.

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --An active weather day is expected with several rounds of showers
and thunderstorms possible. There is also potential for strong
to severe thunderstorms and localized flash flooding, mainly
this afternoon into this evening.

Visibilities have improved across the area and the fog advy has
been allowed to expire.

Attention turns to a closed upper low and associated strong
trough and its associated frontal system. Several subtle
shortwaves rotating around the upper low will move through the
region this morning. Showers are isolated to start the day, but
trends indicate there is potential for coverage to expand later
this morning into early afternoon, especially from the NYC metro
on NW. Thunderstorms should remain below severe limits during
this time period. The pre-frontal trough looks to move into
western portions of the area late this afternoon and early this
evening, shifting eastward into tonight. Dynamics in the middle
levels also become more supportive of convective development in
the afternoon and evening.

The main concern for strong to severe thunderstorms comes this
afternoon and evening. Forecast soundings indicate 1000-1500
J/kg of CAPE, largely surface based north and west of the I-95
corridor in NE NJ into the interior Lower Hudson Valley. There
is also a decent amount of CAPE in the hail growth zone, about
300-500 J/kg. Bulk shear values look to average around 30 kt,
but could increase to 35 kt this evening as the flow increases
aloft. There could be some discrete cell development across NE
NJ and the Lower Hudson Valley this afternoon which will then
transition to more of a linear structure late afternoon or early
evening. The main threat is from damaging wind gusts,
especially if a line of storms develops. However, given the
amount of CAPE in the hail growth zone, hail to around 1" in
diameter is also possible. An isolated tornado is also possible
west of the NYC metro, especially if cells remain discrete late
in the afternoon before the expected line moves across in the
evening.

SPC has expanded the slight risk to include all of the Lower
Hudson Valley with no significant change to the rest of the
outlook (slight risk across NE NJ, NYC metro, western LI and
marginal elsewhere).

There is still uncertainty in how the severe storm threat
evolves as into Hudson River corridor on east. A bit more of a
SE flow closer to the NYC metro into Long Island and Connecticut
should bring a fairly strong low level inversion, so surface
based CAPE may end up lower. However, strong forcing from the
approaching upper trough and closed low and pre-frontal trough
could be enough to support a severe storm threat into the NYC
metro and western LI before any remaining line of storms weakens
further east. It is also possible that the line weakens as it
gets into the NYC metro as it encounters the marine environment.
The later timing may also help with weakening. Another factor
that could lower the severe threat is if several rounds of
showers/storms occur earlier in the day, helping to work over
the atmosphere a bit.

There is also a localized flash flooding threat as any shower or
thunderstorm could produce locally heavy rainfall. WPC has a
marginal risk of excessive rainfall across much of the area with
a slight risk across interior NE NJ and interior Lower Hudson
Valley. The consensus of guidance along and the 00z HREF PMM
signals the heaviest rainfall to fall through tonight across NW
NJ into a portion of Orange County into E PA. 1-hr and 3-hr FFG
in Orange County are high (close to 3 inches). Have held off on
a flood watch. However, if trends later today indicate
increasing potential for higher rainfall amounts into NE NJ or
Lower Hudson Valley, a short-fused watch could be issued.

The severe storm threat diminishes overnight, but showers and
thunderstorms are possible, especially across Long Island and
Southern Connecticut as the pre-frontal trough moves eastward.-- End Changed Discussion --

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
The region may lie in a relative min in any convection Tuesday
morning. The guidance has continued to signal the initial area
of instability and lift east of the area in the morning.
However, there could be subtle shortwaves in the flow that may
bring a shower or storm ahead of potentially more organized
convection Tuesday afternoon and evening as the vertically
stacked low and frontal boundary approach. Instability should
increase, especially from the NYC metro on north and west. This
will likely bring another round of showers and thunderstorms.
There is still some uncertainty in the convective environment
and how much the atmosphere is able to recover from Monday. SPC
has the eastern half of the area in a marginal risk in its
latest Day 2 outlook. Locally heavy rainfall is possible with
localized flash flooding potential across NE NJ and the Lower
Hudson Valley. Have adjusted PoPs to better reflect the latest
model trends. Precip probabilities are generally in the chance
category in the morning and then increase to likely east and
categorical north and west late in the afternoon and evening.

Showers and few storms are possible the first half of Tuesday
night, but lowering instability should help diminish coverage
heading into Wednesday morning. The upper trough axis will
remain to our west on Wednesday with the surface boundary in
the vicinity. These features all support increasing chances for
showers and thunderstorms, especially in the afternoon and
evening.

It will remain muggy Tuesday and Wednesday, but high temperatures
will likely stay below average for this time of year in the upper
70s to around 80 degrees.

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
The unsettled pattern will continue through the long term, with
the only chance of a brief reprieve and perhaps more intervals
of sunshine overall towards Fri / Sat.

The upper trough and closed low will only slowly move overhead
into Thursday. Shower and scattered t-storm activity remains
possible, especially in the afternoon and evening. The trough
and associated frontal system may start to shift to the east on
Friday with weak high pressure trying to settle, but confidence
how this evolves is still quite low. 700mb RH values from
deterministic models would suggest some moments of sun in
between periods of clouds on Friday.

Look for daily max temps to average below normal with a good
deal of daytime cloud cover anticipated on average throughout
the period. There may be a day towards Fri or Sat where daytime
temps may get closer to normal. Night minimums should average
close to normal with higher humidity due to a persistent
southerly flow and a good chance of night time cloud cover.
Mainly used NBM for temperatures.

Late Saturday into Sunday another frontal system will approach
us from the west increasing southerly flow and thereby
increasing available moisture and keeping temperatures warm.

.AVIATION /13Z MONDAY THROUGH FRIDAY/...
A low pressure trough remains nearby through early morning.
Another trough moves into the region later today along with a
warm front to the west.

VFR across the NYC terminals right now with some lingering
stratus and fog elsewhere. These conditions are expected to
improve over the next few hours. However, scattered showers and
thunderstorms this morning could bring conditions back down to
MVFR or lower.

There will likely be a short lull period sometime late this
morning before showers and thunderstorms return through the
evening. There is potential for stronger thunderstorms in the
late afternoon, especially from the NYC metro terminals and
north and west. Heavy rain, gusty winds and even small hail are
possible. MVFR/IFR likely with any thunderstorm. Only put TSRA
in a small window in the TAF when thunder is most likely, but
any activity today as the potential to produce lightning.

MVFR to IFR cigs return tonight.

The afternoon KJFK haze potential forecast is red...which
implies slant range visibility less than 4SM outside of cloud.

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

The greatest chance for thunderstorms is late this afternoon,
but any activity today has the potential to produce lightning.
Picked the most likely window in the TAF to include TSRA.
Stronger thunderstorms are possible, with gusty winds, and
small hail possible.

OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...

Tuesday and Wednesday: Showers. Tstms with gusty winds and hail
possible, especially afternoon/evening. MVFR cond expected, IFR
possible. Tuesday S winds G20-25kt.

Thursday: Chance of showers and a slight chance of tstms. MVFR or
lower possible at times.

Friday: Becoming VFR.

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

.MARINE...
-- Changed Discussion --The dense fog advisory has been allowed to expire. Some fog may
also persist out east through the afternoon which has occurred
the last few afternoons.

Otherwise, both winds and seas are expected to remain below SCA
criteria through the day before increasing southerly flow helps
build seas to around 5 ft tonight. Winds may also come close to
25 kt on the ocean, especially on Tuesday with seas 5 to 7 ft.
Seas are expected to remain elevated into Wednesday night
decreasing during the day on Thursday. Conditions then largely
remain below SCA through the rest of the period, with the
possibility of 5 ft waves over the ocean waters Friday night.-- End Changed Discussion --

.HYDROLOGY...
There is a continued risk of minor flooding and localized flash
flooding, mainly late this afternoon into this tonight in
showers and thunderstorms. WPC has a marginal risk of excessive
rainfall across much of the area with a slight risk across
interior NE NJ and interior Lower Hudson Valley.

A localized risk of flash flooding continues on Tuesday, mainly
across NE NJ and the lower Hudson Valley. However, locally heavy
rainfall is possible in any showers or thunderstorms which could
produce minor flooding.

Hydrologic impacts are also possible Wednesday into Thursday,
but may be dependent on where the heaviest rainfall occurs
through Tuesday. WPC currently has a marginal risk of excessive
rainfall N of the region both Wednesday and Thursday.

.TIDES/COASTAL FLOODING...
The moderate risk of rip current development continues for all ocean
beaches today. The risk is high on Tuesday due to stronger
southerly flow and higher seas.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 PM EDT
Tuesday for ANZ350-353-355.-- End Changed Discussion --