247
FXUS61 KOKX 050609
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
209 AM EDT Wed Jun 5 2024

.SYNOPSIS...
High pressure will be in control tonight. A warm front approaches on
Wednesday and passes through during Wednesday night into Thursday
morning. This will be followed by a cold frontal passage at night.
Thereafter, a broad area of low pressure will reside across eastern
Canada through the weekend before exiting offshore early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
More low stratus than fog with current observations. Made the areas
of fog in the forecast, patchy fog until 08Z. Then kept areas of
fog in the forecast mainly along the coast, with more patchy fog
inland.

Adjusted cloud coverage forecast as well through daybreak.
Temperatures are on track.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
From the morning into the start of the afternoon, the low
clouds and fog will be slower to dissipate for Long Island and
to the south but expecting a decrease in coverage for the latter
half of the morning.

In the afternoon, any remaining fog burns off and low clouds
scatter out for most locations expect along immediate coastline.

Only other weather feature for the afternoon into this evening
will be pop up showers and thunderstorms. These will be forming
well ahead of an approaching warm front. With combination of
where surface based CAPE will be relatively highest (up to a few
hundred J/kg) and where low level winds will exhibit more
convergence, that will be the western extremes of the region.
That is where there will be a chance for showers and
thunderstorms with otherwise in the nearby vicinity to the east,
a slight chance of showers and thunderstorms. Expecting any
convective activity to stay primarily to the north and west of
NYC.

With mainly a dry day expected, high temperatures away from the
coast are forecast to rise into the low to mid 80s with the rest
of the area in the 70s. High temperatures forecast were from the
NBM.

A warm front arriving from the west is forecast to push through most
of the forecast area by the end of Wednesday night. Moisture deepens
with PWATs increasing to nearly 2 inches. Combined with the lift
ahead of the advancing front, showers become likely west to east
starting early evening. Some elevated CAPE will be present, so an
isolated thunderstorm will be possible. Shear profiles and limited
CAPE will mitigate the severe thunderstorm potential. The steering
flow increases overnight, so flash flooding is not a concern during
this period. Minor nuisance/urbanized flooding is still possible
however.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The forecast period will generally be unsettled into early next
week as multiple upper vorticies track across eastern Canada
and in close proximity to the Northeast. Global models do have
some differences with the wavelength separation between these
features and the overall evolution and interaction. This will
impact the location and the trajectory of shortwave energy
rotating about these features.

Before then though, a frontal system out ahead of the first
upper vortex dropping into the Great Lakes sends a warm front
through the area Thursday morning, followed by a pre-frontal
trough and cold frontal passage in the late afternoon/evening
hours. The bulk of the rainfall comes in the early morning
hours ahead of the warm front, with the area getting into the
warm sector for much of the daytime hours. Airmass is moisture
laden with PWAT around 2 inches. This combined with a pre-
frontal trough/cold front should trigger showers and thunderstorms
that work into the area during the late afternoon/evening
hours. There is decent CAPE, but narrow and more typical of slow
rising updrafts. Expect there to be heavy downpours, but
steering winds will be on the order of 30 kts. So any flood
threat should be brief and more of the minor nuisance variety.
Storm total rainfall is from 0.50 to 1.00" with some locally
high amounts possible. Once again, most of this comes with the
the warm advection early in the morning. Severe threat is low.

Following the cold frontal passage Thursday night, there will
be a chance of showers and thunderstorms through the period,
but mainly in the afternoon hours as shortwave energy rotates
about the main upper vortex north of the area. This does not
look like a washout at this time based on the area being more on
the southern side of the system with a subsident westerly flow.
Rain chances are generally 20 to 40 percent during this time,
highest across the interior. This is subject to change though
due to complexities previously mentioned in the upper levels.

Temperatures on Thursday will also be complex due to a southerly
flow with high dew point air potentially keep coastal areas
enshrouded in low clouds/fog, while areas from NYC north and
west could get some decent heating in the warm sector. This will
depend on how much clearing these areas see. Used a blend of
the NBM and NBM50th for warmer values away from the coast (low
to mid 80s), but a blend of CONSALL and NBM to account for the
cooler coastal areas (low to mid 70s). Cooler air will be slow
to advect into the region behind the cold front. Used a blend
of the NBM and CONSALL to reflect values closer to normal
Saturday through Monday, with a gradual warmup heading into
Tuesday.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
High pressure remains off the New England coast through the TAF
period. A frontal system begins to approach late Wednesday into
Thursday.

Areas of fog and stratus develop into Wednesday morning with
the persistent onshore flow. IFR cigs have already moved into
KJFK as of 530Z, and should spread to most other terminals thru
8Z or so, then IFR or lower cigs and vsbys thru 12Z. Improvement
into mid morning, but could linger into late morning for some.
VFR expected Wednesday afternoon, before conditions lower to IFR
or below once again Wednesday night with showers developing.
Embedded thunder can`t be ruled out overnight into Thursday
morning, but chance is too low to include at this time.

Southerly flow persists thru the forecast, speeds at or under 10
kt.

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

Lower confidence on timing of sub VFR conditions tonight into
Wednesday morning for KLGA/KTEB/KEWR and this may be off by
a couple of hours. Amendments possible.

Timing of category declines and SHRA Wednesday evening may be
off by a few hours.

Isolated thunder possible late Wednesday night into Thursday
morning.

OUTLOOK FOR 06Z WEDNESDAY NIGHT THROUGH SUNDAY...

Late Wednesday Night: IFR or lower with SHRA.

Thursday: MVFR or lower possible in showers and thunderstorms,
mainly during the daytime hours.

Friday: Chance of MVFR with showers and possible thunderstorms.

Saturday/Sunday: Chance of MVFR in showers.

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

&&

.MARINE...
Not much low stratus and fog seen on satellite at the moment, but
expecting both to develop and expand across the waters overnight.
Might need to eventually issue a dense fog advisory, but
currently don`t have enough confidence in timing and placement
without any ground truth.

Conditions will otherwise continue to remain below SCA levels
through Wednesday night with a relatively weak pressure gradient in
place.

SCA chances increase on the ocean Thursday into Thursday night
with non-ocean waters likely remaining below SCA thresholds.
Ocean seas may linger near 5 ft early Friday before lowering
under weakening SW flow. Thereafter, conditions are expected to
remain below SCA levels through the weekend.

&&

.HYDROLOGY...
There are no hydrologic concerns through Wednesday afternoon.
Rainfall amounts of 0.50 to 1.00" with localized higher amounts
are expected late Wednesday night into Thursday. Minor nuisance
poor drainage flooding will be the primary threat.

&&

.TIDES/COASTAL FLOODING...
With the approach of a new moon this week, astronomical levels are
on the rise. A southerly, then southeasterly, flow will also support
increasing surge this week. This should be sufficient to get some of
the vulnerable locations along the western LI Sound and the South
Shore Bays at or just above minor flood benchmarks. A Coastal
Flood Advisory remains in effect for coastal Fairfield,
Westchester, and Nassau for this evening`s high tide, with a
Coastal Flood Statement in place for coastal Queens, where the
most vulnerable spots may see brief minor flooding. Based on
latest trends, this may have been more of a statement level
event tonight as water levels will likely only get to around
minor flood benchmarks.

The persistent flow and astronomically high tides will likely
lead to additional minor flooding in subsequent evening high
tides into late this week.

There is a moderate rip current risk on the ocean beaches through
Thursday due to building seas and a strengthening southerly flow.

&&

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

&&

$$

SYNOPSIS...JC/DW
NEAR TERM...JC/JM/JT/DW
SHORT TERM...JC/JM
LONG TERM...DW
AVIATION...DR/JT
MARINE...JC/DW
HYDROLOGY...JC/DW
TIDES/COASTAL FLOODING...