000
FXUS61 KOKX 211425
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1025 AM EDT Sat Oct 21 2023
.SYNOPSIS...
Low pressure south of Long Island strengthens as it moves towards
Rhode Island and SE Massachusetts and then into the Gulf of Maine
today into tonight. The low eventually moves into the Canadian
Maritimes by early Sunday. The low will then slowly move
eastward and weaken for the remainder of Sunday and into Monday.
By Monday, high pressure starts to build in from the west. This
high will be centered over the area early Tuesday and remain in
control through at least midweek. A weak cold front may move
through the area sometime at the end of the week, with high
pressure returning thereafter.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Based on stlt, buoy, and lightning data, low pres was estimated
to be centered about 200 mi SE of NYC at 14Z. No big changes to
the fcst attm, other to remove tstms from the nwrn 1/3 of the
cwa with the sys now starting to translate ewd.
Vorticity maximum shifts east of the region this morning into
this afternoon. Larger scale in mid levels exhibits a
negatively tilting trough with cutoff low forming by early
this evening in the Gulf of Maine.
At the surface, low pressure will be strengthening as it lowers its
central pressure value on its way towards SE Massachusetts this
morning. The low is expected to continue to strengthen and
deepen as it moves into the Gulf of Maine for this afternoon
into this evening.
Rainfall lingers especially across Southern Connecticut and Long
Island where rainfall will remain likely through much of the
day. Some of the rain could be heavy at times with some enhanced
lift. Farther west, for NYC, NE New Jersey, and the Lower
Hudson Valley, outside of the possibility of some brief
instances of light rain from time to time, mainly dry
conditions are expected for the afternoon.
The pressure gradient will be tightening late this morning
through this afternoon in response to the strengthening low
pressure area moving into coastal New England. Winds were
adjusted to above model guidance to account for mixing down in
the model BUFKIT soundings. Generally, expecting gusty westerly
winds. Winds will range around 15 to 25 mph with gusts around
35 to 45 mph.
Wind gusts could potentially exceed 45 mph for some coastal
locations this afternoon especially along Long Island and
Southern Queens, but did not feel confident enough on the
frequency of occurrence. Feel the probabilities are still low
enough to not put up the wind advisory after assessing 10m wind
gust potential fields from the HRRR plus the upper percentiles
of wind gusts from the NBM. These datasets depict the 40+kt wind
gusts staying mainly offshore.
In addition, the lingering rain will mean mixing efficiency will
not be optimal as lapse rates will be more moist adiabatic and
less dry adiabatic. If rainfall is less than forecast and drier
air works in faster than previous forecast, then wind gusts
potential could increase in the subsequent forecast.
With the rain, overcast conditions as well as breezy flow,
temperatures will be staying below normal. Forecast highs are
mainly in the upper 50s to near 60.-- End Changed Discussion --
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Mid levels convey cutoff low moving into Canadian Maritimes with
another trough approaching from the west. At the surface, strong
low pressure will be moving from the Gulf of Maine into the
Canadian Maritimes.
Rainfall is expected to taper off in the evening for the eastern
parts of the region. Abundant clouds will remain. Used a blend
of raw model data consensus, MOS consensus and NBM for the
temperature forecast, ranging from the lower 40s to lower 50s
for the lows.
For Sunday, the trough will be moving across and will allow for
more clouds than sun and perhaps a brief light rain shower for
interior parts of the region with mid level positive vorticity
advection. Pressure gradient will still be tight allowing for
breezy westerly flow although winds will be of less magnitude
compared to the previous day and night.
A colder airmass will be developing in the region as main upper
level jet winds stay south of the region. Forecast high
temperatures on Sunday are mainly in the range from the low 50s
to the upper 50s.
For Sunday night, winds will decrease further but clouds will
remain abundant, mitigating radiational cooling. Lows forecast
range mainly in the low to upper 40s.
For Monday more ridging aloft takes place, allowing for greater
subsidence and more sun as surface high pressure starts to
build in from the west. Winds will further decrease and another
cooler than normal day is forecast for high temperatures Monday
which will be mainly in the lower 60s.
More optimized radiational cooling occurs Monday night with
mostly clear sky conditions and winds becoming nearly calm as
high pressure center moves overhead. There continues to be
potential for frost in outlying and interior parts of the
region. Lows will trend colder, ranging from the lower to mid
30s for outlying, interior sections to near 50 within NYC.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Tranquil weather expected from Tuesday onward as high pressure will
remain in control through at least midweek. Several dry days with
sun can be expected. With a southerly flow setting up as the high
pushes off the East Coast Tuesday, temperatures through the week are
expected to be seasonably warm.
Global guidance is not in as good agreement for the end of next
week. Right now it looks like there is potential for a weak cold
front to pass through and bring some light showers. Given the
uncertainty, just stuck with NBM for PoPs which was mostly dry.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
An area of low pressure rapidly deepens just east of the area today.
High pressure builds in tonight.
Conditions vary from VFR to LIFR across the terminals and will
continue to do so mid morning, but should average out to be MVFR.
A return to VFR is expected by mid morning (after 16Z for the
metro terminals), however it could be later than forecast
(possibly until 19Z).
Showers expected through this morning. An isolated thunderstorm is
not entirely out of question, though confidence and coverage remains
too low to include in TAFs. Some of these showers will be
associated with moderate to heavy rain, with brief reduction in
visibility. Showers come to an end from west to east late this
morning into this afternoon.
Light and variable winds become NW this morning. Speeds
substantially increase late this morning, 20 to 25 kt with gusts
30 to 35 kt through this evening. Gusts diminish somewhat
tonight, but will still be in the 25 to 30 kt range.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of category changes and wind shift could be off by a few
hours.
Isolated thunderstorm possible at terminals through this morning.
Isolated gusts up to 40 kt possible this afternoon.
OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY...
Tonight: VFR. Gusty NW wind 15-20G25-30kt.
Sunday: Mainly VFR. W to NW wind gusts around 25-30 kt.
Monday: VFR. Gusty NW flow 15-20 kt in the morning.
Tuesday: VFR.
Wednesday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Already have SCA level seas on the ocean. Pushed earlier the
timing of the gale warning so that it is already in effect. The
non-ocean waters have their gale warning the same as before,
going into effect at 12PM this afternoon. For all marine zones,
the gale warning goes until 6AM Sunday.
SCA level conditions for the wind gusts remain on all waters
Sunday and into Sunday night but non-ocean waters are forecast
to start to lower below SCA late Sunday night. The ocean remains
with SCA level conditions for both wind gusts and seas Sunday
through Sunday night.
With greater influence of high pressure, conditions trend to
below SCA for all marine zones Monday into Monday night with the
weakening pressure gradient.
Thereafter, with high pressure in control, conditions will be below
Small Craft Advisory criteria through Wednesday morning. Waves build
to 5 ft on the ocean waters Wednesday afternoon with an increasing
SW flow developing, diminishing late Wednesday night into early
Thursday morning.
&&
.HYDROLOGY...
Additional rainfall of between 0.5 and 1.5 inches of rain is
forecast across mainly Long Island and Southern Connecticut
through early this evening. Some locally higher amounts are
possible with potential for minor flooding in poor drainage
areas. Otherwise, no hydrologic problems are expected.
There are no hydrologic concerns Sunday through next week.
&&
.TIDES/COASTAL FLOODING...
From the prolonged onshore fetch and piling of water, a few
sites in and around the South Shore Bays and possibly the lower
NY Harbor could reach minor coastal flood benchmarks for the
afternoon high tide cycle today. One mitigating factor will be
the NW offshore flow developing and increasing during the day.
Water levels are expected to stay below minor coastal flood
benchmarks. There could be an isolated occurrence where a tide
gauge just reaches its minor coastal flood benchmark for
instance near Freeport or Montauk, but confidence on this is
not high.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...None.
NJ...None.
MARINE...Gale Warning until 6 AM EDT Sunday for ANZ331-332-335-338-340-
345.
Gale Warning until 6 AM EDT Sunday for ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JM/JP
NEAR TERM...JMC/JM
SHORT TERM...JM
LONG TERM...JP
AVIATION...JP
MARINE...JM/JP
HYDROLOGY...JM/JP
TIDES/COASTAL FLOODING...