-- Discussion containing changed information from previous version are highlighted. --
647
FXUS61 KOKX 301605
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1205 PM EDT Sun Jun 30 2024

.SYNOPSIS...
A cold front will move across the region this afternoon and
evening. High pressure then builds in Monday and will remain
in control through Wednesday. A warm front lifts north of the
area on Wednesday Night followed by a cold front late in the
week which may remain nearby into the first half of next
weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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*** SEVERE THUNDERSTORM WATCH UNTIL 7 PM THIS EVENING ***

Radar has already been showing convective initiation to the
immediate NW of the CWA. This activity gets further E and SE as
time progresses. There is already activity along the pre-
frontal trough across Eastern PA and this is main area of
concern into this afternoon, with the cold front further to the
west potentially firing up a second area / round of convection
which could behave more in a linear fashion and have impacts
into the first half of this evening for eastern and southeastern
portions of the area. Mesoscale parameters are rather
impressive despite some cloud cover across the area. More
clearing as occurred into Eastern and Central PA and this works
east along with further destabilization going through the
afternoon. Eastern portions of the area have dealt more with
lower level clouds, but this will push east and burn off. Thus a
Severe Thunderstorm Watch has been issued for the entire CWA.
The forward motion and speed of the developing activity will
ultimately determine if the Watch will need to be extended in
time for eastern portions of the area. Forecast remains on
track, with higher confidence of severe convection as SPC has
just about the entire area in an Enhanced risk of severe
t-storms, along with the watch now in place. Previous discussion
still holds with respect to the mesoanalysis and follows.

The pre-frontal trough will move in ahead of the front early
this afternoon and will likely be the convergence mechanism to
initiate convection around 12-3pm well north and west of the
NYC metro. The convection should continue to develop and
organize eventually into a line of storms that will move south
east across the area through the rest of the afternoon and early
evening. The actual cold front will follow quickly behind the
pre-frontal trough and could initiate a few more showers and
storms early in the evening before any lingering convection
pushes offshore.

The main threat from the thunderstorms will be from damaging
wind gusts in excess of 58 mph. There is also a risk of hail
and an isolated tornado cannot be completely ruled out. SPC has
continued to highlight a slight risk across the entire area. The
timing of the highest risk for severe thunderstorms appears to
be between about 3pm and 9pm based on the SPC experimental
timing graphics. The main uncertainty with the timing is whether
or not the pre-frontal trough convection will be predominate
and have the greatest chance at being severe or will it be with
the actual cold front. In either case, the earlier timing in the
aforementioned range favors the interior with the later
afternoon and early evening for locations closer to the coast
including the NYC metro and Long Island.

The ingredients for potential severe thunderstorms include an
unstable environment with MLCAPE values 1500-2500 J/kg and
SBCAPE values 2000-3500 J/kg. Some CAMS even indicate SBCAPEs
pushing 4000 J/kg, especially away from any maritime influence.
Bulk shear values increase through the day with an approaching
middle and upper level shortwave. There looks to be about an
average of 35-45 kt of 0-6 km shear, especially in the afternoon
and evening. Winds are mostly unidirectional, but enhanced
surface convergence from storm outflow could support a few
rotating updrafts and an isolated or brief tornado. The region
will also lie in the right entrance of a jet streak over
northern New England and southeast Canada, which should help
support the convection into the early evening.

PWATs look to range from around 1.75 to around 2 inches with
subtropical moisture pooling along the approaching boundary.
While locally heavy downpours are likely, the flash flood risk
is low and isolated due to the relatively fast steering flow and
progressive nature of the convection. Minor urban and poor
drainage flooding is most likely.

Another concern with the convection will be from frequent
cloud-to-ground lightning. Forecast soundings show a decent
amount of CAPE in the -10C to -30C region of the profile which
typically is a sign that once the convection organizes there
will likely be frequent lightning. The CAPE in this zone also
supports the risk of hail.

Highs today will be in the middle to upper 80s for most with
potential of hitting 90 in urban NE NJ. Heat indices should
reach around 90 for much of the area with close to 95 in the
NYC and urban NE NJ corridor. The cold front will push south and
east of the area this evening and should be offshore after
midnight. Some showers/storms may linger near the coast after
9pm, but most of the activity should be ending thereafter. Much
drier and cooler air will begin working in behind the front with
dew points falling into the 50s and low 60s by early Monday
morning.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
The upper trough will pivot across New England on Monday. The
progression of the trough will be slow enough that a few showers
may develop across eastern CT and the east end of Long Island
Monday afternoon. These would be associated with energy within
the trough that may attempt to close off near the New England
coast. Otherwise, high pressure will slowly build in from the
Great Lakes region. Mainly partly cloudy skies are expected
although it could trend mostly cloudy out east in the afternoon.
Highs will be a bit below normal for July 1 ranging from the
upper 70s inland to around 80 near the coast. The pressure
gradient ahead of the building high pressure will support N
gusts 20-25 mph.

The trough pushes offshore Monday night with ridging building
behind it into Tuesday. The surface high will also settle over
the area by Tuesday. Dry conditions will continue with highs
moderating to seasonable levels in the lower to middle 80s for
Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
No major changes were made to the Long Term and closely followed
the NBM.

High pressure will remain in control on Wednesday before
shifting offshore Wednesday night as a warm front lifts to the
north. A cold front will follow, but will likely not move
through the area and may remain to our north into early next
weekend. Will have to watch the evolution of any middle level
impulses as they ride along the periphery of the ridge. These
are difficult to resolve at this time range, but they may be a
focus for showers and thunderstorms. Right now the consensus of
the modeling indicates a bit higher probability on Friday and
potentially Saturday compared to Thursday.

Temperatures remain seasonable on Wednesday. The deterministic
NBM has trended down a bit for the end of the week, but still
should reach above normal levels, with highs in the upper 80s to
lower 90s away from the coast. Similar readings are expected
through Saturday. Humidity levels will also be on the rise for
the end of the week into next Saturday.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
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A pre-frontal trough moving across the area this afternoon will
be followed by a cold front moving across this evening.

Some MVFR conditions linger across some of the coastal terminals
going into early this afternoon with sub-IFR at KGON, mainly due
to low stratus. Otherwise, MVFR or lower conditions will be
possible with some thunderstorms this afternoon and evening.

Two rounds of thunderstorms are forecast for this afternoon and
evening. The first of these with the pre-frontal trough should
impact the Hudson Valley terminals from 16Z-19Z, the NYC metros
from about 19Z-21Z, and out east across Long Island/CT from
20Z-22Z. The second round with the cold front should occur from
late afternoon into the evening, impacting the NYC metros from
22Z-23Z until 01Z-02Z, once again about an hour earlier to the
NW and an hour or two later to the E. Stronger cells with either
round could produce strong W-NW winds, mentioned in the 1st
round of thunderstorms in TAFs with potential for 35 kt, and
possibly brief 50 kt gusts. These strong gusts are also possible
with 2nd round of thunderstorms but not explicitly mentioned in
TAFs yet.

Outside of tstms, S-SW winds 5-10 kt should become more SW and
increase to 10-15G20kt by afternoon. After cold fropa this
evening, winds shift NW around or just over 10 kt, with some
terminals gusting to 15-20 kt.

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

Strong wind gusts possible with any tstm directly impacting the
terminals this afternoon and evening.

OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY...

Monday through Wednesday: VFR.

Thursday: Possible MVFR or lower possible with any late day or
nighttime showers/tstms.

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

&&

.MARINE...
-- Changed Discussion --
A severe thunderstorm watch is in effect across all waters
through 7 pm this evening.

Thunderstorms develop this afternoon across the western most
waters, and should push east and south through the afternoon and
into this evening for the eastern most waters. Strong, gusty, to
potentially damaging winds, and frequent lightning can be
expected, and hail with any storms. The storms push further
offshore late this evening into the overnight.

The SCA on the ocean remains in effect through midnight. A cold
front will approach the waters this afternoon and move across
this evening. Showers and thunderstorms may bring locally higher
winds and seas. Conditions will subside below SCA levels
overnight behind the front.

Winds and seas should remain below SCA levels through the week.
However, late day winds in the NY Bight area just E of Sandy
Hook could gust close to 25 kt each afternoon Wed through Fri.
-- End Changed Discussion --

&&

.HYDROLOGY...
Showers and thunderstorms are likely this afternoon and evening
with locally heavy downpours. The main hydro threat with this
activity is from minor urban and poor drainage flooding. There
is a low risk for localized flash flooding.

Locally heavy rainfall is also be possible the end of the
upcoming week.

&&

.TIDES/COASTAL FLOODING...
A high rip current risk continues into this evening with swells
of 5-6 ft and 7 second period. Seas and swells subside a bit on
Monday with the flow becoming N. Have gone with a moderate rip
current risk for Monday, which is supported by the latest RCMOS
guidance.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
NY...High Risk for Rip Currents until 9 PM EDT this evening for NYZ075-
     080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ350-353-
     355.
-- End Changed Discussion --

&&

$$

SYNOPSIS...JP/DS
NEAR TERM...JE/DS
SHORT TERM...DS
LONG TERM...JP/DS
AVIATION...BG
MARINE...JP/DS
HYDROLOGY...JP/DS
TIDES/COASTAL FLOODING...