-- Discussion containing changed information from previous version are highlighted. --
132
FXUS61 KOKX 271142
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
742 AM EDT Mon May 27 2024

.SYNOPSIS...
A strong frontal system impacts the area through tonight. A
series of reinforcing cold fronts will then move across the
area during the middle of the week. High pressure builds in
Friday into the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Visibilities have improved across Long Island and widespread
dense fog is no longer anticipated. The dense fog advisory
remains in effect for coastal CT until 9 am. Visibilities
should slowly improve through 9 am.

A warm front lifts north of the area this morning. A narrow line
of showers with embedded thunder continues to move towards the
area. There should be some weakening of this line as it
continues towards the NYC metro, NE NJ, and Lower Hudson Valley
due to less instability. A brief downpour and rumble of thunder
is possible through around 8 am. Otherwise, a pre-frontal
trough will then push into the area this afternoon and evening
and will be quickly followed by a cold front passage overnight.

Here are some key messages on the shower/thunderstorm potential
through tonight:

* A few rounds of showers and embedded thunderstorms are expected,
  first for mainly areas west of the city, then spreading east in
  the afternoon and evening.

* The primary threat continues to be minor/poor drainage flooding.
  There is a localized flash flood threat, especially for locations
  north and west of the NYC metro. WPC continues to place NE NJ and
  portions of the Lower Hudson Valley in a slight risk for excessive
  rainfall, with a marginal risk elsewhere.

* The severe thunderstorm threat has increased a bit with the
  western half of the area now in a slight risk for severe
  thunderstorms. The main concern is from damaging wind gusts and
  hail to around 1" in diameter.

* Conditions will quickly dry out from west to east tonight with the
  majority of the convection offshore by midnight.

There may be a few showers as warm advection increases with a
strengthening low level jet this morning. Many of the CAMs
signal a brief lull in any convection until the early afternoon
as a more organized line of showers and thunderstorms develops
along the pre- frontal trough. This main line of convection will
be the one of concern for potential of localized flash
flooding. There may be a few other pockets of showers that
develop ahead of this line, but not anticipating them to cause
any issues other than brief moderate to heavy rainfall. A
consensus of the latest CAMs brings the main line of showers and
thunderstorms across NE NJ and the Lower Hudson Valley this
afternoon and early evening, NYC metro late in the afternoon and
early evening, and Long Island and Southern Connecticut this
evening.

The onshore flow will likely limit surface instability, but
elevated instability looks supportive of organized convection.
A modest middle level flow and vigorous middle level impulse may
be enough to help bring down higher winds with any stronger
updrafts, and this is the reasoning for the slight risk for
severe thunderstorms across the western half of the area. The
severe risk appears very limited east of the NYC metro and
Hudson River due to stronger onshore flow influence.

PWATs should rise to around 1.75 inches, which is close to the
daily observed max for May 27th per SPC sounding climatology.
Locally heavy downpours are likely in the convection and any
areas that may receive training of heavier cells could see the
localized flash flood risk. The overall system is progressive
enough and the rain will not come in one widespread batch. This
will limit flooding impacts, so no flood watch has been issued
at this time. Storm total rainfall ranges from 0.5 to 1.25
inches with locally higher amounts possible. The HREF
probabilities for greater than 1 inch in one hour remain low,
but do reach around 10-15 percent late this afternoon and early
evening across portions of NE NJ into the interior Lower Hudson
Valley.

The cold front quickly follows the pre-frontal trough helping to
push the deep moisture and lift eastward with improving conditions
expected after midnight.

Highs today will only be in the lower to middle 70s. If some
breaks develop west of the city, highs could push closer to 80.
This will have to be watched as it could lead to slightly
higher surface instability. Some fog may linger across eastern
Long Island and southeast Connecticut into the afternoon. The
increasing onshore flow and mixing should prevent the fog from
being dense.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
The deep moisture axis and initial shortwave will continue
pushing offshore Tuesday morning. A larger upper trough will
then linger over the eastern CONUS. Another shortwave within the
trough pushes towards the area through Tuesday afternoon. The
atmosphere dries out significantly behind the lead wave and the
forcing is weak, so will leave the forecast dry. The initial
cold front that moves across late Monday into Monday night
should be offshore, but a surface trough may setup over eastern
Long Island/southeast Connecticut Tuesday. Otherwise, Tuesday
looks mostly sunny and warm. Winds should take on a more
westerly component allowing temperatures to reach the upper 70s
and lower 80s across the region. Some middle 80s are possible
across NYC metro.

Low pressure continues to track across New England Tuesday
night dragging another weak front or surface trough across the
area. Another area of middle level energy dives southeastward
into Wednesday morning and rounds the base of trough into
Wednesday. The trend in the latest guidance has been
weaker/flatter with this system. Models had hinted at a wave of
low pressure developing nearby Wednesday, but chances are a bit
lower. It is possible this system develops Wednesday night or
Thursday. Have lowered PoPs through Wednesday evening and will
not just have slight to low chance late in the day. Temperatures
will be in the 70s across the area.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
An upper level trough remains over the region to start to the
long term with an mid level shortwave moving across the region
on Thursday.

There continue to be differences with the progression of
shortwave energy within the upper trough. The GFS continues to
be more progressive with this feature, while the ECMWF has
remained fairly consistent with a slower, stronger system. The
latter of which reflects a surface low to the south of the area,
For now, will continue to carry just some chance POPS during
this period. Expecting at least a chance of showers areawide
Wednesday night into Thursday. Confidence remains somewhat low
during this time. The shortwave moves away from the region
Thursday night with drier air moving into the area.

Attention then turns to the upper trough closing off just
offshore on Friday. There clearly has been an eastward progression
of this low, which in turn leads to a mainly dry forecast with
surface high pressure building into the area over the weekend.
There are then timing issues with a frontal system progressing
from the west which could bring showers into the region next
Sunday. Right now, expecting a mainly dry weekend. A better
chance of showers returns on Monday.

Highs in the long term will generally remain in the 70s each day,
with the warmest of the day Sunday and Monday, where a few
locations may come close to 80 west of NYC.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
A frontal system approaches today and moves across the area
tonight.

Conditions range from MVFR to LIFR this morning in stratus and
fog. Many of the terminals saw their vsbys improve to 5-6 miles,
however the low cigs remain. Uncertainly with just how much we
improve today, especially right behind this line of showers
moving across the city terminals. Will improve conditions to
MVFR for KLGA and KJFK and MVFR with a brief period of VFR for
KEWR and KTEB. For the remainder of the terminals, expecting
mainly an IFR or lower day, with low end chances of improvement
to MVFR.

There is an increasing likelihood of rounds of SHRA and embedded
TSRA this afternoon and into the first part of tonight.
ConditioNS then fall back down to IFR or lower until 09-13z,
with winds become more westerly and and improvement to VFR is
expected. It may take slightly longer for the far eastern
terminals to see improvement.

S-SE around 10 kt or less will increasing to 10-15G20-25 kt for
the late morning/early afternoon. Winds speeds fall back to 10kt
or less tonight. Late tonight and early Tuesday morning, winds
become more SW or W.

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

Amendments likely today for changing flight categories. Timing
of showers and thunderstorms may be off by 1-2 hours.

OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...

Tuesday: IFR/MVFR early, improving to VFR. SW winds
10-15G20kt.

Wednesday and Thursday: Late Night/AM MVFR/IFR stratus/fog
potential. Otherwise VFR, with chance of aftn SHRA/TSRA.

Friday: Mainly VFR.

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

&&

.MARINE...
Dense fog advisory remains in effect on the waters until 10 am
Monday. Dense fog may linger past 10 am on some of the waters, but
confidence is not high enough yet to extend the advisory.
Want to wait to see how observations trend to see if there is any
improvement after sunrise.

A strengthening SE flow this afternoon will likely result in wind
gusts around 25 kt on the ocean, first west of Fire Island Inlet and
then the rest of the ocean this evening. Winds will start to fall
below 25 kt, especially after the pre-frontal trough passage and
strongest flow pushes east. However, seas are likely to build to
around 5 ft this evening into tonight. Have gone ahead and issued an
SCA on the ocean, starting at 19z west of Fire Island Inlet and at
22z east of there. The SCA runs through 10z Tuesday. Conditions
should then remain below SCA levels through Wednesday.

winds and seas will generally remain below SCA criteria for the
middle and end of the week.

&&

.HYDROLOGY...
Showers with embedded thunderstorms are possible this morning and
early afternoon, mainly west of the NYC metro. A more organized band
of showers and thunderstorms is expected to move across the region
from around middle afternoon into this evening. Locally heavy
rainfall is possible with the highest rainfall totals are most
likely to occur across portions of NE NJ and the Lower Hudson
Valley. This is where WPC continues with a slight risk for excessive
rainfall. These locations should to see around 0.75-1.25 inches with
locally higher amounts possible. The rest of the area continues to
be placed in a marginal risk. The primary threat appears to be
minor/poor drainage flooding with a localized flash flood threat,
especially where the heaviest rain/training convection ultimately
occurs.

&&

.TIDES/COASTAL FLOODING...
A strengthening southerly flow ahead of a frontal system will allow
for building surf today with the rip current risk increasing to
moderate in the afternoon. A moderate rip current risk continues on
Tuesday due to 3 to 4 ft seas continuing on the ocean. This is
supported by the latest RCMOS.

Additionally, isolated minor coastal flooding will be possible with
tonight`s high tide cycle. A statement may be needed for the south
shore back bays of Nassau County.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Dense Fog Advisory until 9 AM EDT this morning for CTZ009>012.
NY...None.
NJ...None.
MARINE...Dense Fog Advisory until 10 AM EDT this morning for ANZ331-332-
     335-338-340-345-350-353-355.
     Small Craft Advisory from 6 PM this evening to 6 AM EDT
     Tuesday for ANZ350-353.
     Small Craft Advisory from 3 PM this afternoon to 6 AM EDT
     Tuesday for ANZ355.

&&

$$

SYNOPSIS...BC/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...BC
AVIATION...BC
MARINE...BC/DS
HYDROLOGY...BC/DS
TIDES/COASTAL FLOODING...