-- Discussion containing changed information from previous version are highlighted. --
835
FXUS61 KOKX 252354
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
754 PM EDT Sat May 25 2024

.SYNOPSIS...
High pressure will give way to a weakening frontal system this
evening into early Sunday. A surface trough lingers on Sunday. A
stronger frontal system will affect the area Monday into Monday
night with a series of fronts following it Tuesday into Wednesday.
An upper level disturbance may impact the area towards the end of
next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
Upstream convection across central NY State south into NE PA
continues to weaken as it works east into a stable airmass.
This weakening is also supported by the CAMs. Thus, only
expect  isolated coverage as the activity work west to east
overnight.

At the surface, weak high pressure will slide east giving way
to a weakening pre-frontal trough/cold front this eventing.
Models indicate enough lift for isolated showers overnight.
Moistening S/SE flow should allow for advection/development of
stratus across coastal areas tonight into Sun Am. Potentially
some fog advection/development along the immediate coast of
LI/SE CT as well.

Lows will be in the upper 50s and lower 60s.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
Zonal upper flow aloft with heights gradually rising Sunday. Brief
shortwave ridging will slide east Sunday night, giving way to
approach of a series of shortwaves Sunday Night thru Monday in
deep SW flow ahead of a broad northern plains/Great lakes low.

Weak troughing lingers across the region on Sunday. A lingering
early morning shower threat before shortwave energy moves east.
The surface trough likely retrogrades inland in the afternoon
with the development of a hybrid SE synoptic/sea breezes. No
discernible trigger for convection in the afternoon/evening,
along with mid-level capping, should keep any shower/tstm
activity chances slight and isolated along the interior trough.
With a bit more in the way of cloud cover on Sunday (morning
stratus/aft cu) but otherwise similar synoptic setup, and well
inland moving aft sea breeze, temps will likely be very similar
to today. Convection will quickly dissipate Sun eve, with
stratus and fog likely working back onshore into coastal areas
Sun night.

A frontal system approaches the region Sunday Night into Monday,
with warm front lifting north Monday morning, and then pre-frontal
trough approaching late Mon/Mon eve. Scattered shower possible late
Sun night/Mon AM with warm frontal passage, particularly western
areas, then increasing shower threat expected from w to e during the
the afternoon Monday with approaching main shortwave and
strengthening llj advecting in a +2 STD PWAT Atlantic/Gulf
airmass. Elevated instability will also be on the increase from
SW to NE late Mon into Mon eve, increasing the threat for rounds
of heavy downpours and embedded thunderstorms along and ahead
of the pre- frontal trough/cold front into Mon Night.

NBM ensemble probs of >1" of rainfall by 8pm are about 10-20%,
particularly for hill terrain N&W of NYC with orographic enhancement
in SE flow. Will have more insight into rainfall amounts and rates
for this event over the next 24 hrs as the event gets resolved by
high-res CAMs.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Moderate to occasionally heavy showers with embedded thunderstorms
will continue, especially the first half of Monday night, associated
with a strong frontal system. Forecast area looks to be mainly north
of the warm front, possibly briefly warm sectored. Instability is
mainly elevated with high helicity with the SE low-level inflow. So
not favorable for severe weather, but will have to watch how close
the warm front gets, and if some higher surface based instability
can be generated. Cold front is quickly on its heels with conditions
drying out by daybreak Tuesday. PWAT values are near 1.75, which is
around the daily max for this date. Some of the rainfall could be
briefly heavy. WPC has areas north and west of NYC in a slight risk
of heavy rainfall and marginal elsewhere. There are some timing
issues, but consensus has trended a bit faster. Storm total rainfall
is currently expected to be between 0.50 to 1.00", highest north and
west of NYC and across interior southern CT.

Thereafter, another strong shortwave drops into the mean trough
across the Great Lakes and Northeast Tuesday into Wednesday.
There are series of reinforcing cold fronts/troughs that move across
the area during the time. There was a possibility of the airmass
recovering ahead of the cold front on Wednesday, but airmass looks
capped and too dry to support strong convection. What has changed
through is the chance of post-frontal showers, possibly a
thunderstorm Wednesday night into Thursday in associated with the
aforementioned shortwave. The upper trough then closes off just
offshore Friday into Saturday. Have kept a slight chance of showers
during this time. This will depend on the proximity of the closed
low to the forecast area. Farther west, and there could be more
clouds and convection.

As for temperatures, largely followed the NBM for all except
Tuesday, where it was blended with the warmer 50th percentile. The
box and whisker temperature plots from the NBM show the
deterministic below the 25th percentile at most sites. A WSW flow
and dry air point to the potential for a warmer day with many
locations getting into the lower 80s, possibly warmer in the metro
area. This will depend on how quickly the cooler air follows.
Otherwise, expect temperatures getting closer to normal in the
Thursday through Saturday time period. The coolest day look to be
Thursday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
A weakening cold front approaches late tonight and stalls
nearby on Sunday.

VFR early this evening. LIFR stratus anticipated at
KJFK/KISP/KBDR/KGON overnight before dissipating by mid-Sunday
morning. Slight chance of showers after midnight for the city
and terminals and KSWF/KHPN. IFR or lower may return aft 00Z
Mon.

SE-S winds bcmg more S-SW or light and variable by the end of
the night. S-SE flow aob 10kt on Sun.


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

Chance that low cigs and vsbys do not occur tonight at KJFK. A
low chance that low cigs and vsbys spread to KLGA after
midnight.

OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...

Sunday Night: IFR or lower possible. Chc TSTM for KSWF/KHPN.

Monday: IFR. Chc morning showers, then PM showers likely and chc
of TSTM. SE gusts 20-25kt possible for coastal terminals.

Tuesday: IFR/MVFR early, improving to VFR by noon.

Wednesday: Chance of aftn TSTM and MVFR.

Thursday: Mainly VFR. Slight chc shra/TSTM.

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

&&

.MARINE...
A weak pressure gradient and lack of significant swell will lead
to conditions below SCA levels through Sunday night. A strengthening
S-SE flow on Monday could into result in marginal SCA
conditions on the ocean waters, mainly late in the day into the
first half of the night.

A strengthening S-SE flow on Monday could into result in marginal
SCA conditions on the ocean waters through  Monday night. Otherwise,
Winds and seas will generally remain below SCA criteria for the
middle and end of the week.

&&

.HYDROLOGY...
A frontal system Monday into Monday night will likely bring
a few rounds of heavy rain showers and embedded thunderstorms
Monday afternoon into Monday Night.

Predictability remains inherently low on location of axis of
heaviest rainfall, peak rainfall magnitude and rainfall rates, which
should become more clear over the next 24 to 36 hrs as this event is
better resolved by high-res CAMs. Chances remain highest for
heaviest rainfall across NE NJ, the Lower Hudson Valley, and
interior southern CT. These locations are likely to see around
and inch of rainfall with locally higher amounts possible.

6hr Headwater guidance for minor flooding along flashy rivers is
around 2 to 2 1/2", while 12 hr is closer to 3". At this point NBM
exceedance probabilities are not indicating this, but will need to
properly assess this potential through high-res model guidance.

WPC continues to highlight a slight risk for excessive rainfall
to the north and west of NYC with a marginal risk elsewhere. Primary
threat appears to be for minor urban/poor drainage flooding,
with a flash flood threat in the path of any training
convection (slight risk area).

&&

.TIDES/COASTAL FLOODING...
A southerly flow at 5-10 kt and a southerly swell of 1 ft 8-9s
should keep the rip current risk low through Sunday.

The rip current/longshore current risk will likely increase to
moderate through the afternoon Monday as E/SE winds strengthen
and SE wind waves build to 3 to 4 ft.

This forecast is supported by latest RCMOS at area beaches.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...NV/DW
NEAR TERM...NV/DW
SHORT TERM...NV
LONG TERM...DW
AVIATION...JMC/JC
MARINE...NV/DW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...