351
FXUS61 KOKX 290238
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1038 PM EDT Fri Jun 28 2024

.SYNOPSIS...
High pressure pushes of the coast tonight, with a warm front
approaching Saturday and moves through late in the day. A cold
front approaches late Saturday night. A cold front passes late
on Sunday. High pressure follows it on Monday and lasts into
mid- week. Another frontal system may impact us Thursday into
Friday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY 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.

Dew points are expected to rise from the 40s to lower 50s into
the upper 50s to lower 60s by daybreak. Additionally, low
temperature 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 SATURDAY MORNING THROUGH SUNDAY/...
The actual warm front is not expected to move through the area until
late in the day Saturday, 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 Saturday 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 Saturday night.
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
Saturday and Saturday night, leading to PWAT values in the 2.00" to
2.75" range. 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 2 am to 8 am Saturday night into
Sunday morning.

The potential for strong to severe 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 for Saturday into Saturday
night. Surface based instability will be on the rise Saturday night,
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 on Saturday 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 THURSDAY/...
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 on Saturday 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 /03Z SATURDAY THROUGH WEDNESDAY/...
High pressure remains in control through tonight, pushing
further offshore Saturday. A slow moving frontal system
approaches Saturday Night.

VFR tonight, then MVFR ceilings become increasingly likely late
tonight into Sat AM push for western terminals. Cigs likely
improve to VFR during late morning into early afternoon, before
returns Sat eve/night.

Light S/SE winds tonight into Sat AM push, increasing to 10 to
15g20kt by late Sat AM. S/SE G20-25kt likely for most terminals
Sat aft.

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

MVFR conditions likely for Sat AM push, and possibly returning
by Sat eve push. SHRA/TSRA possible after 00z. Timing of MVFR
stratus and SHRA/TSRA may be off by an hour or so.

S/SE winds 15-20G25kt likely for KJFK/KLGA Sat aft, with
occasional gusts to 30 kt possible.

OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...

Saturday Night: Increasing likelihood of MVFR/IFR conds with
SHRA/TSRA potential Sat eve into overnight.

Sunday: MVFR or lower possible with AM and PM SHRA/TSRA
potential.

Monday thru Wednesday: VFR.

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

&&

.MARINE...
Conditions are expected to remain below SCA criteria through
Saturday as high pressure remains in control. With southerly flow
increasing over the waters, the ocean and south shore bays should
see winds gusts of 25 to 30 kt starting Saturday afternoon
continuing into Sunday afternoon. A SCA has been issued for
these waters. All other waters, confidence was not high enough
to issue SCA, but it is certainly possible. Waves will increase
over the ocean waters as well in response to the increased
southerly flow. 5 to 6 ft waves on the ocean is expected 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 PWATS increasing to 2.00" to 2.75" 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 Sat morning, quickly
increasing to a high risk by Saturday afternoon with
strengthening S/SE winds and wind waves.

A high Risk of rip currents is expected through Sunday with
5-6ft@7sec orthogonal swell.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents from 6 AM EDT Saturday through Sunday
     evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...Small Craft Advisory from 2 PM Saturday 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...NV
MARINE...JP/BR
HYDROLOGY...JP/BR
TIDES/COASTAL FLOODING...