809
FXUS61 KOKX 102150
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
450 PM EST Tue Dec 10 2024
.SYNOPSIS...
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A stationary front will lift north as a warm front late tonight
into Wednesday morning. A strong frontal system will affect the
area Wednesday into Wednesday night. A secondary cold front
moves through Thursday, followed by strong high pressure
building over the region into the weekend. A weakening
disturbance approaches late in the weekend, before another
frontal system potentially impacts the area early next week.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Anomalous, longitudinally deep trough digs down to the
Mississippi Gulf coast tonight, with deep SW upper flow ahead
of it tonight. At the surface, a series of southerly lows track
north along a stationary cold front running from the Gulf coast
into the Ohio valley/Great Lakes, with a warm front slowly
working north towards the region overnight. The warm front will
lift north late tonight into early Wed AM, as a coastal llj
strengthens and expands north into the region.
E/NE flow to the north of the approaching warm front will maintain
low clouds and patchy fog/drizzle into the first half of
tonight, with increasing likelihood of showers overnight into
early Wed AM with WCB approaching the region and a deep layered
lift of a +3-4 STD PWAT airmass over the region.
Evening low temps from the lower 40s to near 50 should increase
through the 50s for the coast, while holding in the mid to upper
40s across interior valleys overnight.-- End Changed Discussion --
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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Anomalous, longitudinally deep trough digs down to the
Mississippi Gulf coast Wed AM, negatively tilts and pivots into
the Mid Atlantic Wed eve, and then across the area Wed Night.
At the surface, warm front lifts north Wed AM, with a series of
low pressure waves tracks north along the eastward moving cold
front approaching the region Wed AM into aft, and then crossing
Wed eve.
Initial area of moderate to heavy rain associated with head of
strengthening llj and northward moving warm front may briefly
subside in the late AM/early afternoon for western areas, while
potential for this to continue for LI/S CT under strengthening
llj.
This will be followed by main axis of moderate to heavy
rainfall associated with deep layered lift (divergent flow ahead
of vigorous upper trough axis and under right front quad of
150kt ulj) and strong moisture convergence and lift ahead/along
approaching cold front in the aft/early eve as a result of a
weakly unstable +3-4 STD PWAT airmass being advected in on a
75-80kt llj. Embedded tstm activity possible as a weakly
unstable airmass advects into the region.
High-res cams indicating a fine line of low-topped convection
likely organizing along the cold front, although timing
differences on how quickly the line gets organized across areas
w of NYC. Generally moving from w to e across the region
between noon and 8pm. Higher model confidence in this line
consolidating across LI/S CT. Rainfall rates of 1+"/hr possible
with this line. A few hours of post-frontal moderate rain likely
behind the front before coming to an end Wed eve. Overall, a
general 2-3" of rain likely areawide, with locally 4-5" possible
across LI/S CT if/where most persistent banding develops.
Overall, primary threat is for minor urban, poor drainage and
even small stream flooding, so no Flood watch issuance at this
time. See hydro sections for rainfall details and potential
flood impacts.
The 75-80 kt llj overspreading the coast Wed aft into early
eve, combined with only a weak low-level inversion will present
potential for damaging wind gusts across LI and SE CT, with wind
advisory winds gusts for the remainder of the coastal plain,
including NYC. BUFKIT analysis and HRRR wind gust potential
support a high wind warning for LI, coastal New Haven, and
Middlesex and New London counties for 55 to 60 mph gust
potential (localized 65mph gusts possible for east end of LI),
50 to 55 mph gusts potential for the next tier of counties
inland. Winds shift to the W with cold frontal passage Wed
evening, and continue gusty with cold advection (25-35 mph,
locally 40 mph, much of the night)
Unseasonably mild temperatures of 60-65 on Wed should quickly drop
after cold fropa Wed evening, with lows in the lower 30s by
daybreak Thu.-- End Changed Discussion --
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
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Key Points...
* Sharply colder behind midweek system, wind chills in the 20s
Thursday and Friday afternoon
* Turning milder and unsettled early next week as a frontal system
potentially impacts region
Strong CAA follows the cold frontal passage into Thursday, with a
secondary front moving through late in the day. The parent low
pressure deepens as it tracks into Quebec, and surface high pressure
begins to build in from the west. This tightened pressure gradient
will keep a strengthened flow in place. The cold air aloft should
allow mixing toward 850 mb, keeping conditions blustery through the
day with westerly gusts 30 to 40 mph. With 850 mb temps progged
around -11C to -13C, afternoon temperatures should only achieve the
mid 30s inland to the lower 40s for eastern areas. With the gusty
conditions, expect wind chills in the 20s through the day, if not
lower. Absent a stray flurry in the interior, conditions remain dry
under mostly sunny skies.
Winds weaken by Friday as the center of the high approaches.
Sunshine prevails, but conditions remain colder than normal with
highs only in the low to mid 30s and morning wind chills in the
teens. The strong 1047 mb surface high passes just north of the
local Tri-State into Saturday, and the flow veers around and becomes
onshore by Sunday as the center slips into the Canadian Maritimes.
This will help nudge temperature up from the 30s and 40s Saturday to
the 40s and low 50s Sunday. Increasing low level moisture with the
flow should lead to a good amount of lower clouds on Sunday as a
weak mid level wave and warm front approach, though it remains
unclear if the associated precip dissipates before reaching the
area. Another frontal system may move through early next week, but
guidance disagrees with timing and intensity. Kept PoPs capped at
chance (50%) for now until the picture becomes clearer, but at this
time the first few days of next week appear unsettled. Left ptypes
at rain and/or snow at this stage, but more likely would be either
all rain or perhaps a wintry mix well inland based on soundings and
warmer air moving in aloft.-- End Changed Discussion --
&&
.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
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A warm front just to the south slowly lifts north into tonight.
Elongated low pressure and its associated cold front approach
overnight. LIFR and IFR prevail through tonight with ceilings
remaining below 1 kft, and in most cases below 500 ft. Some pockets
of reduced visibility at a few terminals in FG this evening. Rain
spreads west to east across the terminals tonight starting at 00z or
shortly thereafter.
Winds veer further and become more SE-S tonight and increase. The
winds become gusty late tonight with LLWS possible as early as the
start of the Wednesday morning push for city and western most
terminals. By 12-15z LLWS should prevail at most terminals as gusts
get to 30 kt by 15z, and approach 35 to 45 kt for the city and
eastern terminals towards 18z.
NY Metro (KEWR/KLGA/KJFK/KTEB)TAF Uncertainty...
Amendments likely regarding ceiling and visibility changes
throughout the TAF period. Confidence has increased with cigs
remaining below 1000 ft through at least 21Z Wednesday.
OUTLOOK FOR 18Z WEDNESDAY THROUGH SUNDAY...
Wednesday afternoon / night: IFR and rain, likely heavy at times.
Chance of thunder. S gusts increase with LLWS through the day, with
gusts potentially up to 40-50kt afternoon into the early evening -
highest gusts likely east of the city terminals. Winds veering SW in
the evening with MVFR, then more W overnight with VFR returning
towards midnight and gusts still around 30kt.
Thursday: VFR with W winds 15-20G30kt.
Friday and Saturday: VFR.
Sunday: sub VFR possible in light rain and low clouds, especially
late.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
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Sub SCA conds into tonight.
Low pressure and its associated cold front will impact the
waters Wed into Wed evening. Southerly winds and ocean seas will
quickly increase to SCA early Wed AM, and then Gales by midday
Wed. As strong LLJ moves across a period of storm force wind
gusts are likely across most waters, except NY harbor. Rough
seas are expected with this system, up to 4-7 ft on the Sound
and 12-18 ft on the ocean late Wednesday into Wednesday night.
Once the strong low level jet passes Wed eve, westerly gales
are expected in its wake Wed Night into Thu Am.
Gales are likely to continue through Thursday afternoon on at
least the ocean, and potentially on the non-ocean waters. Winds
lower below 25 kt on all waters by Thursday night and ocean seas
gradually lower from over 10 ft Thursday morning, to under 5 ft
by late Friday morning. Sub SCA conditions then persist on all
local waters Friday into early next week.-- End Changed Discussion --
&&
.HYDROLOGY...
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A widespread 2-3" of rainfall likely from late tonight into Wed
evening ranges from 2-3 inches. Locally 4 to 5" amounts are
possible across LI/S CT where high-res models are indicating
bands of heavy rain persistently moving north thru the region
late tonight into early Wed aft, and followed by a consolidating
e-w moving axis of heavy rain/embedded thunder ahead/along the
cold front.
Rainfall rates of 1+"/hr possible in this line. This line will
be progressive, but will occur over already saturated ground
from earlier 1-2" rain over LI/CT and may expand in size as it
moves east with better llj forcing.
Headwater guidance indicating that 2"/6hr or 3"/12hr would be
sufficient for minor flashy small stream flooding. Moderate
potential of this occurrence is across S CT.
Otherwise, the primary threat from this rainfall will be minor
urban and poor drainage flooding, with rainfall rates of
generally 1/4 to 1/2"hr between 6am and 6pm, with brief
3/4-1"/hr rates possible. This will be most persistent across
LI/S CT. There is a localized risk of flash flooding where
higher rates persist, particularly S CT.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
As little as 1 1/4 to 1 1/2 ft surge needed for minor coastal
impact with the Wed AM high tide. With as little as 2 1/2 ft for
the evening high tide.
With easterly flow tonight causing some tidal piling, and
southerly winds just beginning to ramp up during the morning
high tide, water levels will approach minor flood thresholds and
perhaps touch in a few spots across SW CT and southern
Queens/Nassau.
While peak surge is expected to occur Wed afternoon and early
evening, stillwater levels for most locations should once again
remain below minor flooding benchmarks. But with a gradual
windshift from southerly storm force to SW SCA just before or
during the time of evening high tide, potential for areas along
the southern bays of NYC LI, south facing shoreline of twin
forks, and coastal CT to see minor coastal impacts from combo
of elevated water and splashover from wave action. This includes
the eastern Great South Bay as water levels may remain elevated
and could touch minor benchmarks as a strong southerly flow
switches to the southwest, preventing water from escaping the
bay quickly.
The combination of 10-15 ft breakers during the evening high
tide will cause widespread beach flooding and erosion.
Scattered area of dune base erosion, and localized washovers
possible for LI beaches where dunes protection is compromised.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Wind Advisory from noon to 10 PM EST Wednesday for CTZ005-006-
009.
High Wind Warning from noon to 10 PM EST Wednesday for CTZ007-
008-010>012.
NY...Wind Advisory from noon to 10 PM EST Wednesday for NYZ071>075-
176-178.
High Wind Warning from noon to 10 PM EST Wednesday for
NYZ078>081-177-179.
NJ...Wind Advisory from noon to 10 PM EST Wednesday for NJZ006-104-
106-108.
MARINE...Storm Warning from noon to 10 PM EST Wednesday for ANZ331-332-
335-340-345-350-353-355.
Gale Warning from 6 AM Wednesday to 6 AM EST Thursday for
ANZ338.-- End Changed Discussion --
&&
$$
SYNOPSIS...NV
NEAR TERM...DR/NV
SHORT TERM...DR/NV
LONG TERM...DR
AVIATION...JE
MARINE...DR/NV
HYDROLOGY...DR/NV
TIDES/COASTAL FLOODING...NV