000
FXUS61 KOKX 251545
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1045 AM EST Mon Dec 25 2023

.SYNOPSIS...
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Weak high pressure over the region today slowly weakens through
Tuesday night as the system shifts east. Low pressure approaches
on Wednesday and passes nearby Wednesday night into Thursday.
Another low may develop nearby on Friday and then move offshore
on Saturday.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
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Fog has been lifting this morning with no need to issue another
special weather statement for patchy dense fog. Breaks in the
clouds have developed over parts of the forecast area and have
adjusted the forecast accordingly. Tough call as to whether if
and how quickly clouds will fill back in during the daytime
hours. Thinking is that better chances of fewer clouds will be
over eastern LI and SE CT, but a partly cloudy/mostly sunny
rest of the day could be possible elsewhere.

Cutoff upper low slides southeast over the region today, and
then SE of the region tonight. At the surface, weak inverted
trough across far eastern portions of the region this morning
will gradually weaken today. High pressure re-establish itself
tonight.

Temps will be 8 to 10 degrees above seasonable (upper 40s
interior to lower 50s city/coast). Might need to adjust this
upward should it become more apparent that it won`t remain
mostly cloudy for most of the rest of the day in some area.

Drying aloft in wake of closed low, continued weak low level
onshore flow under subsidence inversion, and nocturnal cooling
will favor stratus development and areas of fog (locally dense)
once again tonight.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Shortwave upper ridging briefly builds into the region Tuesday ahead
of developing central US upper low, before flattening Tuesday Night
ahead of eastward drifting large central US trough. At the surface,
high pressure overhead on Tuesday gradually slides east offshore
Tuesday Night.

Dry conditions on Tuesday, but once again stratus may be stubborn,
particularly western portions of the region on edge of high
pressure. Highs once again about 10 degrees above seasonable, upper
40s interior to lower 50s city/coast, and once again if any
afternoon breaks of sun are realized, could be even warmer in
spots.

Attention turns to large closed upper low and associated trough
developing over the Central 2/3rd of the US. Models have come into
good agreement with this feature, with only a slow ESE drift of this
feature expected thru the Mid-Mississippi River Valley into
Tennessee River Valley through Wednesday Night. At the surface,
cold front associated with weakening stacked Central Plains low
will slowly work towards the eastern coastal plain Tuesday Night
into Wednesday.

A strengthening sub-tropical jet will work up the Mid Atlantic Coast
Wednesday into Wed night in deep SW flow ahead of the closed upper
low. General model agreement in this inducing low pressure along the
cold front over the southern Mid-Atlantic working up the coast, but
model spread in the degree of intensification and track of this low.
This will be predicated on the exact evolution of the closed low as
it begins interacting with northern stream trough over SE Canada.

Increasing potential for showers across far western portions of the
region Tuesday Night with strengthening SE flow and theta-e
advection. Deep layered lift of Atlantic moisture feed (+1-2 STD
PWATs) gradually increases areawide from SW to NE Wednesday
afternoon into Wed eve with broad upper level divergence ahead
of approaching shortwave rotating around upper low, lift in
vicinity of left front of ULJ streak, and modest strengthening
LLJ ahead of surface low. This will present potential for a 6-9
hr period of heavy rain as this progressive frontal system moves
through. Operational NBM probability for 1" of rain in 24 hr is
up to 55 to 65%, and 2" of rain is up to 10 to 20% (reasonable
worst case scenario). There has been a slow upward trend in
this over the last 48 hours, and based on potential lift and
moisture, would expect these amounts to trend upward if stronger
low pressure intensification scenarios verify. Storm total
rainfall range of 3/4" to 1 1/2" likely at this time, with
reasonable worst case of 2", highest amounts across areas W and
NW of NYC. Rainfall amounts will depend on eventual track and
intensification of the surface low, a farther north and stronger
low increases the threat for higher end of forecast rainfall
range.

With 6hr headwater guidance for flashy NE NJ rivers around 1
1/4" and widespread streamflows still above 75th to 90th
percentile, the threat for minor flood impacts along a few to
several quick responding rivers in NE NJ is increasing. The
threat for minor flood impacts along a few flashy rivers across
Lower Hud and S CT is increasing as well. Soil moisture
anomalies are also running at 99th percentile areawide, lending
to a scattered minor urban/poor drainage flood impact
potential.

In terms of winds, based on LLJ strength, a period of SE 25 to 35
mph wind gusts possible Wed aft/night ahead of the surface low,
which is climatologically unremarkable.

General agreement on low pressure and cold front moving east by
Thursday morning, with drying conditions.

Temps continue well above seasonable, with overnight lows Tue and
Wed Night, warmer than normal highs for this time of year.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A complex weather pattern will continue for the end of the week
leading to a continuation of unsettled weather. This has led to
lower predictability with regards to potential additional low
pressure development Thursday night into Friday.

*Key Points*

* First low pressure that impacts the region passes to our northeast
  on Thursday.

* Another low may develop nearby to the region Thursday night into
  Friday, but confidence is low at this time with whether it will
  bring any additional precipitation.

* Above normal temperatures Thursday transition to seasonable
  temperatures next weekend.

Deterministic global models and their ensembles continue to differ
with the handling of a closed low/upper trough that tracks towards
the east coast Thursday into the end of the week.
The models seem to be struggling with the handling of energy from
yet another upper low over SE Canada. Some of this energy could dive
southward and interact with the remaining trough over the east. The
complex interaction is where the models differ.
There are hints at another surface low developing either over the
region or just south of the area on Friday. The handling of the
upper trough will play a role in whether or not the low deepens
(GFS), or remains broad and weak (ECMWF, CMC) on Friday.
The NBM was used for PoPs during this period due to the
aforementioned large amount of uncertainty. This yields a chance PoP
continuing through the end of the week.

There are indications that the upper trough will begin shifting
offshore for next weekend, but unknown if it will be by next
Saturday or next Sunday.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
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High pressure will remain over the terminals through the TAF
period.

Area of IFR/LIFR conds persists across much of Long Island, SW
CT, and nearby portions of NYC and the lower Hudson Valley
(KLGA/KISP and KJFK vicinity). Think conds there will eventually
improve to at least MVFR by about 18Z, with mainly VFR
elsewhere.

Improvements will be fairly short lived as conditions
deteriorate this evening. Widespread IFR/LIFR appearing likely
tonight especially overnight.

Mainly light and variable flow through the TAF period although
could have a E-NE flow 5-7 kt at times.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
AMD likely for changing flight categories.

The afternoon KJFK, KLGA, and KEWR haze potential forecast is
YELLOW, which implies slant range visibility 4-6SM outside of
cloud.

OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...

Tue: MVFR or lower at times.

Wed: MVFR or lower with rain.

Thu-Fri: MVFR possible. Chance of showers. NE winds G20-25kt
possible on Fri.

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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Will likely allow the dense fog advisories expire this morning
as widespread visibilities are over 1 nm. More widespread dense
fog possible over waters tonight.

Otherwise, conditions are forecast to remain below SCA
thresholds through Wed morning with a relatively weak pressure
gradient in place.

Chances then increase for SCA conditions on the ocean, and
possibly nearshore waters, late Wed into Wed Night ahead of
approaching low pressure. The chance for SCA conditions
continues on Thursday on the ocean due to seas, but winds
should remain below 20 kt. All waters could potentially see 25
kt wind gusts Friday into Friday night, with elevated seas
remaining on the ocean, as stronger westerly flow develops.
-- End Changed Discussion --

&&

.HYDROLOGY...
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Storm total rainfall range of 3/4" to 1 1/2" likely Wed into
Wed Night, with reasonable worst case of 2". Highest amounts
across areas W and NW of NYC with orographic enhancement of SE
flow. Most of this likely falls in a 6 to 9 hr period. 6hr
headwater guidance for flashy NE NJ rivers is around 1 1/4", and
with widespread streamflows still above 75th to 90th
percentile, the threat for minor flood impacts along a few to
several quick responding rivers in NE NJ is increasing. The
threat for minor flood impacts along a few flashy rivers across
Lower Hud and S CT is increasing as well. Soil moisture
anomalies are also running at 99th percentile areawide, lending
to a scattered minor urban/poor drainage flood impact potential.


More clarity expect on rainfall amounts and hydrologic threat
for Wed/Wed Night in the next 48hrs with increased model
consistency and as high res models resolve this system.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Monitoring potential for minor coastal flood impacts for
vulnerable coastal communities Thu with a passing frontal
system. Tidal departures of 1.25-1.50 ft are needed for minor
flooding, and 2.25-2.50 for moderate flooding during the morning
high tides. About 1 ft additional surge is needed for the
evening high tides.

Potential for minor flooding with the Thu morning high tide
cycle, particularly along the south shore of Nassau and Queens,
and possible along the SW CT coastline on the western Sound.

The threat for dune erosion appears to be low and isolated with
this event.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Dense Fog Advisory until 10 AM EST this morning for ANZ331-332-
     335-340-345.

&&

$$

SYNOPSIS...JC
NEAR TERM...JC/NV
SHORT TERM...NV
LONG TERM...DS
AVIATION...BG/DS
MARINE...DS/NV
HYDROLOGY...DS/NV
TIDES/COASTAL FLOODING...