077
FXUS61 KOKX 290641
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
241 AM EDT Sat Jun 29 2024

.SYNOPSIS...
High pressure pushes off the coast overnight, with a warm front
approaching today and moving through late in the day. A cold
front approaches late tonight, then passes late on Sunday. High
pressure follows on Monday and lasts into mid week. Another
frontal system may impact the area from Thursday into Friday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Zonal flow aloft, while at the surface, high pressure pushes
off the coast.

Return southerly flow develops across the forecast area,
meaning an increase in humidity levels through the night as well
as status likely advecting in from the south ahead of
approaching warm front.

Dewpoints are expected to rise from the 40s to lower 50s into
the upper 50s to lower 60s by daybreak. Additionally, low
temperatures will likely occur well before daybreak. Early lows
should be in the 50s for many places, even a few upper 40s
possible for far outlying areas before beginning to rise late.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
The actual warm front is not expected to move through the area
until late day, so much of the morning will be dry, except
perhaps a passing shower or thunderstorm for Orange County.
Better chances for showers and thunderstorms occur in the
afternoon and overnight with the passage of the warm front and
chances for precipitation continue with the approach of the
prefrontal trough to the west.

Warm air advection continues through the period into tonight.
Low level jet increases during the day and into the first half
of the night, with 925 hPa wind speeds at around 2 am of 30 to
40 kt and is then more limited to eastern areas of the forecast
area through 8 am Sunday. This will continue to bring in a moist
air mass, both at the surface and aloft. Dew points rise into
the 70s today and tonight, leading to PW values over 2 inches.
This does point to the possibility of flash flooding with any
thunderstorms that may move through. SPC HREF is showing a
10-20% chance for 1"+/hr rate from 06Z-12Z Sunday.

The potential for strong to severe tstms is there as well,
mainly N and W of NYC. SPC has placed portions of NE NJ and the
Lower Hudson Valley in a marginal risk for severe storms through
tonight. Surface based instability will be on the rise tonight,
mainly for western areas, where models show SBCAPE values of
500- 1500 J/kg north and west of NYC, while 0-6 km shear values
rise to 35 to 40 kt. Models are also showing a lot of vertical
lift during this time frame. The main threat if severe storms
develop would be damaging winds.

Temperatures today will run at or slightly below normal, with
highs in the upper 70s to lower 80s, but transitions to warm
overnight with lows in the upper 60s to lower 70s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Sunday will see 2 rounds of showers and thunderstorms. One will
occur in the morning with a prefrontal trough. The other, will
occur with a late in the day cold front. All being driven in the
upper- levels by an amplifying trough over the Great Lakes.

Let`s discuss the showers and thunderstorms associated with the
prefrontal trough, first. A strong belt of moisture will set up
along the coast, helped being driven into the area by a 30-40 kt
LLJ (which quickly exits east Sunday morning). The latest model
guidance has PWATs peaking Sunday morning anywhere from 2.2 to
2.6 inches. This is far above the max moving average of 2.03
inches per SPC`s Sounding Climatology Page. Rainfall will occur
aided by our location in the right entrance region of a jet to
our north, areas of mid- level energy passing over, and a
prefrontal trough at the surface. Instability and shear do not
look very impressive, Sunday morning, so any severe weather that
occurs today may not transfer into Sunday morning, but some
heavy downpours could still occur, leading to minor urban
flooding or and isolated instance of localized flashing
flooding. The best timing of the showers and thunderstorms with
the prefrontal trough should have it cleared out and exiting our
area to the east by noon, if not an hour or two before this.

The bigger concern for severe weather will be Sunday afternoon
or evening with the passage of a cold front. 12Z CAMs (NAM,
FV3, RRFS) have a line of showers and thunderstorms developing
along a NE to SW axis in the Lower Hudson Valley in the mid/late
afternoon, then moving southeast into the evening, sweeping
much of the area. The best chance for severe weather appears to
be areas north and west of NYC and around the NYC metro area.
SPC currently places the entire CWA in a Slight Risk area with
CSU-MLP, concurring with this. The main area of concern is
showing strong signs of instability with some models peaking
SBCAPE`s at 4600 J/kg and Bulk Shear 45-50 kts. Lapse rates do
not appear very impressive, but after the morning round of rain,
more sunshine in the interior, could lead to better surface
heating compared the the coast and help aid in storm intensity.
The Energy Helicity Index (EHI) at both 0-3 km and 0-1 km on
some CAMs appears to signal a sufficient risk for rotating
updrafts both in the mid and low levels. The risk for tornadoes
is too hard to pinpoint, for now, but it is a risk that can not
be ruled out at this moment. The same goes for the risk for
hail. Strong to damaging winds associated with the thunderstorms
will be possible for areas both north and west of NYC and
around the NYC metro area. Whether this risk will translate
further east and south on Long Island and in eastern
Connecticut, will really depend on how the morning storms play
out. If the morning storms don`t clear east until after noon
along with dewpoints getting into the mid-70s, things could
appear a little too "muddy" to hold the severe risk in these
areas. These risks will come into better view as more CAMs bring
the event into their sights over the next 24 hours.

Another brief note for Sunday: With high dewpoints expected to
coincide with warm temperatures (highs in the mid/upper-80s to
possibly low-90s) heat indices could peak around 95 to 100 in
the afternoon.

After the front exits, clearing is expected Sunday night into
Monday. The upper trough will swing through the region Monday
and will be followed by ridging into the middle of the week.
Surface high pressure starts to build in from the Great Lakes on
Monday. The high then settles overhead Tuesday before shifting
south and east into Wednesday. The latest modeling indicates a
flatter shortwave ridging around the periphery of the ridge,
which may help lower heights aloft. This may be able to bring a
weaker frontal system towards the area by next Thursday and/or
Friday with most models now depicting a return of rainfall.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
High pressure will move farther offshore today. A slow moving
frontal system will approach tonight.

VFR tonight, then MVFR cigs become increasingly likely late
tonight into the AM push for western terminals. Cigs likely
improve to VFR during late morning into early afternoon before
lowering again tonight.

Light S-SE winds into the AM push should increase to 10-15G20kt
by late AM. S-SE winds G20-25kt likely for most terminals
this afternoon.

There is increasing likelihood of MVFR/IFR conds with
shower/tstm potential tonight.

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

MVFR conditions likely for the AM push, and possibly returning
by the eve push. Showers/tstms possible after 00Z. Timing of
both may be off by an hour or so.

S-SE winds 15-20G25kt likely for KJFK/KLGA this afternoon, with
G30kt possible.

OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...

Late Tonight: MVFR/IFR conds likely with shower/tstm potential.

Sunday: MVFR/IFR cond possible with AM and PM
shower/tstm potential.

Monday through Wednesday: VFR.

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

&&

.MARINE...
With S flow increasing over the waters, the ocean and south
shore bays should see winds gusts of 25-30 kt starting this
afternoon and continuing into Sunday afternoon. SCA has been
issued for these waters. All other waters, confidence was not
high enough to issue SCA, but it is certainly possible. Ocean
seas will increase to 5-6 ft by daybreak Sunday.

Winds will weaken below SCA levels in the afternoon and evening
as a cold front works across the waters. Ocean seas should be
around 5-6 ft on Sunday before subsiding below 5 ft Sunday
night. A relatively weak pressure gradient early next week
should then lead to conditions below SCA levels.

&&

.HYDROLOGY...
With PW increasing to over 2 inches and SPC HREF showing a
10-20% chance for 1"+/hr rainfall rates within the forecast
area late Saturday night, there is the potential for localized
flash flooding from training cells.

Right now, thinking is the most likely scenario is
nuisance/minor urban and poor drainage flooding. However, an
isolated incident of flash flooding cannot be ruled out.

&&

.TIDES/COASTAL FLOODING...
Moderate risk of rip currents expected this morning, quickly
increasing to a high risk by this afternoon with strengthening
S-SE winds and building seas.

The high risk should continue into Sunday with moderate period
swells of 5-6 ft and 7 second period.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents from 6 AM EDT this morning through
     Sunday evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 8 PM EDT
     Sunday for ANZ345-350-353-355.

&&

$$

SYNOPSIS...JP/BR
NEAR TERM...JP/BR/NV
SHORT TERM...JP
LONG TERM...BR
AVIATION...BG/NV
MARINE...JP/BR
HYDROLOGY...JP/BR
TIDES/COASTAL FLOODING...