okx-afd on 2024-12-08

109
FXUS61 KOKX 082335
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
635 PM EST Sun Dec 8 2024

.SYNOPSIS...
Weak high pressure ridge approaches today and shifts offshore
tonight. A weak low pressure center along a warm front moves
through during Monday afternoon and evening, with the warm front
remaining nearby through Tuesday. The region will then be in the
in warm sector Tuesday night into Wednesday with an approaching
cold front to the west. This cold front moves across Wednesday
night. High pressure then returns, building in from the west
Thursday into the next weekend.

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A weak surface high pressure over the area will gradually shift
offshore tonight. This will keep the area mostly dry, though some
high cloud cover may remain overhead as the area remains between a
departing low and an approaching low. ANy gusty winds this evening
should drop substantially overnight and allow for a fairly light and
possibly variable wind to overspread the area. Temperatures tonight
will drop a bit into the 30s for much of the area with perhaps the
exception of the NYC metro which may remain close to 40.

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
By Monday morning, an approaching shortwave trough in the embedded
deep SW to NE flow will approach the area. This mid-level shortwave
forces a low pressure wave to develop along a larger cold frontal
boundary from a parent low pressure system well to the north in SE
Canada. This weaker frontal wave will bring a warm front northward
into the area allowing temperatures to rise into the low 50s for
Long Island and the NYC metro. The center of the low tracks along
the warm front which may bisect the area from north to south. This
low pressure wave will allow for a widespread light to moderate
rainfall to overtake the entire area by Monday afternoon. All areas
are expected to have plain rain as temperatures even for inland
areas are expected to be in the 40s. Overall, a half inch or
slightly less is expected for the entire area.

Rainfall ends as the frontal wave moves through by Monday evening.
As the center of the wave departs, a stalled warm frontal boundary
will remain over the area into Monday night and Tuesday. This will
allow for moisture to be trapped in the boundary layer which will
keep skies overcast. There may be enough moisture at the surface
such that cooling temperatures at night may produce fog and perhaps
drizzle or very light showers. These conditions persist into Tuesday
as s stronger frontal system develops upstream over the Southeast
and interior Mid-Atlantic. Highs on tuesday will be in the middle to
possibly upper 50s for the coast with low 50s for interior
areas.

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Key Points...

* Increasing confidence in a widespread moderate to heavy rainfall
across the region Tuesday night into early Thursday, with flooding
of at least urban and poor drainage areas possible

* Temperatures fall sharply behind midweek system, afternoon highs
10 to 15 degrees below normal to end the workweek

Strengthening upper level trough, baroclinic zone, and surface low
pressure approaching with its associated cold front are the weather
features for the local region Tuesday night through Wednesday night.

For the upper levels, strong upper level low moves from South
Central Canada into the Great Lakes Tuesday night through Wednesday
night. This is part of a deep upper level trough that will be
developing with phasing and tapping into the Gulf of Mexico as it
digs southward Tuesday night and then as it moves east it will
access the Western Atlantic waters for Wednesday. The associated
strong vort max moves across the local region Wednesday night.
Strong shortwave departs well north of the region Thursday, but an
upper level trough remains across the region Thursday into Friday.
The atmosphere transitions to a less amplified pattern with the
trough exiting and weakening for next weekend.

At the surface, the region will be getting into the warm sector as a
warm front will be north of the region. An associated cold front
approaches the region but with low pressure forecast to develop and
strengthen along it, this cold front will not move across until
Wednesday night. Low level warm and moist air advection increase
Tuesday night into Wednesday. See hydrology section for extra
details as precipitable waters are forecast to reach well above
typical levels for this time of year. Low pressure more rapidly
intensifies for Wednesday night into early Thursday morning, with
models indicating around a 15 to 20 mb drop in 12 hours, traveling
from near the region to New England vicinity to Quebec. This strong
low is then expected to move farther north, farther away from the
local region. Meanwhile, high pressure will begin to build in from
the west. This high pressure area will have origins in Alberta,
Saskatchewan and the Dakotas with a very cold airmass moving in.
This high builds in Thursday into the first half of next weekend.

This is setting up a widespread moderate to locally heavy rain
event, especially for eastern sections of the region. This is where
models have their combination of generally where the low level jet
will be and highest precipitable waters. Upper levels have a focus
of the forecast region being in the right rear quadrant of a SW to
NE jet streak for Wednesday into Wednesday night, conveying strong
synoptic lift. Coastal areas could even have an embedded
thunderstorm for Wednesday. This could result in some strong winds
being brought down to the surface, perhaps some wind gusts briefly
up to 50 mph. The eastern areas seen having a higher chance of
getting the heavy rain and gusty winds appears to be Southern CT and
Long Island. However, subsequent model runs will have to be
monitored for any shifts westward with low pressure, low level jet
and heavy rain axis.

Strong cold air advection follows Wednesday night as the low travels
northeast and deepens more rapidly. Would expect ongoing rain to
become more showers and intermittent in period. However, with wet
bulb cooling as drier air tries to work into the region, along with
strong cold air advection, precipitation ends as snow showers
Wednesday night into early Thursday morning.

Temperatures generally above normal Tuesday night and Wednesday and
then near normal Wednesday night. Below normal temperatures for
Thursday through Friday night before airmass moderates going into
next weekend.

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --Low pressure moves northeast into the Canadian Maritimes
tonight into Monday morning. A warm front approaches Monday
afternoon.

VFR expected through Monday morning. Rain with IFR conditions
arriving just after midday and towards the evening push. LIFR
conditions are possible, at times, during the showers. Low end
MVFR conditions return with some periods of IFR still possible
following the exit of the rain showers in the evening.
Development of fog into tomorrow night is very low confidence.
Not currently shown in 00Z TAFs, but may be added in the 06Z
TAFs if more guidance comes in showing better chances for it.

W-WNW winds have subsided below 10 kts this evening. Most TAF
sites go light and variable by 3-6Z tonight. These light and
variable winds continue into early Monday before more of a SE 5-10
kt flow develops preceding the arrival of showers. FOllowing
showers tomorrow evening, winds will be SW 5-10 kts, with some
outlying terminals light and variable.

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

No amendments through the morning push.

Amendments may be needed for lowering flight categories in rain
on Monday.

OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...

Tuesday: MVFR or lower during the day. Increasing chance of rain
late Tue into Tue night. IFR or lower possible at night. Rain will
become more steady at night and increase in intensity.
Southerly wind gusts 15-20 kt developing late at night.

Tuesday night: Steady rain develops Tuesday night with sub
VFR becoming IFR.

Wednesday: IFR likely, possibly sub-IFR at times. Rain may become
heavy at times. S to SW gusts 20-35 kt during day. Possible
thunder and LLWS. W-NW gusts 20-30 kt at night. Potentially
higher gusts possible Wednesday into Wednesday night. VFR returns
late Wednesday night.

Thursday: Mainly VFR with gusty W winds G25-30kt.

Friday: VFR, NW winds.

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

.MARINE...
SCA conditions continue on the non-ocean waters into this evening as
gusts remain near 25 kt. SCA conditions on the ocean persist a bit
longer as wave heights will be slower to come down. Sub-SCA
conditions are expected on the western two ocean zones by
midnight with the eastern ocean zone lingering until 6AM.

Mainly sub-SCA conditions are then expected for all waters on
Monday. As a low pressure center passes overhead Monday afternoon
into the early evening, SCA gusts and wave heights near 5 feet may
result in brief SCA conditions for the ocean zones. This will be
followed once again by sub-SCA conditions on all waters for Tuesday.
SCA conditions rapidly develop on all waters late Tuesday night
and into Wednesday with an increasing S flow ahead of a frontal
system.

SCA conditions continue across all waters into Wednesday, with
gales possible on at least the ocean by Wednesday afternoon. A
period of storm force winds cannot be ruled out Wednesday
evening, particularly on the ocean. Otherwise, SCA conditions
for all waters Wednesday through Thursday. SCA conditions remain
likely on the ocean for Thursday night but for non-ocean
waters, sub-SCA conditions are forecast.

.HYDROLOGY...
No hydrologic issues expected through Tuesday. Heavy rain is
possible at times late Tuesday night through Wednesday with the
potential for flooding in at least low lying and poor drainage
areas. Steady rain, heavy at times, persists Wednesday night
across Southern CT and Long Island. Flash flooding cannot be
ruled out, and WPC has a slight risk of excessive rainfall
across the eastern half of the area on Wednesday, with the rest
in a marginal risk. Model potential for PWATs of near 1.3 to 1.5
inches Wednesday, which would be above the 90th percentile and
around to above the max for OKX sounding climatology for
December 11th.

Total rainfall Tuesday night through Wednesday night ranges from
about 2 to 3 inches, lowest across NYC, interior NE NJ and the Lower
Hudson Valley and highest across SE CT and Eastern Long Island.
There could be locally higher amounts especially across Southern CT
and Long Island. There remains some uncertainty and these rainfall
amounts could shift some in subsequent forecasts.

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 6 AM EST Monday for ANZ350.
Small Craft Advisory until midnight EST tonight for ANZ353-355.-- End Changed Discussion --

SYNOPSIS...DR/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...DR
AVIATION...BR
MARINE...DR/MW
HYDROLOGY...DR/MW