discussion on 2024-04-11

000
FXUS61 KOKX 111356
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
956 AM EDT Thu Apr 11 2024

.SYNOPSIS...
A warm front lifts through and north of the area today as a
deepening low pressure system lifts west of the area. A complex
frontal boundary associated with the low will lift through tonight
into Friday morning. A series of cold fronts or surface troughs
will pivot through during Friday and into the start of the
weekend. A weak low moves through on Sunday. High pressure
takes over Monday, potentially followed by a warm front front
moving in late Tuesday into Wednesday.

.NEAR TERM /THROUGH TONIGHT/...
An SPS has been issued for areas of fog, some of which may
become locally dense for the morning drive as a warm front off
to the immediate south begins its gradual advance north. No
other adjustments for this updated, previous discussion follows.

A stalled frontal boundary will lift north as a warm front this
morning and into this afternoon. With a weak short waves
pivoting through from the SSW expect some showers, especially
further north and west until the early afternoon. Forecast
soundings indicate some drying taking place in the mid levels
for the afternoon, thus mainly cloudy skies are expected in all
likelihood with the majority of the afternoon remaining rain
free as there is good model agreement with this thinking.
Towards later this afternoon with falling heights back to the
west and deepening low pressure over the Ohio Valley, along with
a strengthening high offshore of Labrador and in the NW
Atlantic combine to create an increasing pressure gradient over
the area. The winds start to increase this afternoon, with a
more noticeable increase in the winds shortly after 20-21z for
southern coastal sections. Better forcing along with some PVA
and stronger thermal advection getting into the area very late
in the day and into this evening. Thus PoPs increase to likely
for the western half of the area late in the day. Temperatures
will be near normal closer to the coast, and perhaps a few
degrees above normal further inland to the west where highs
should get into lower and middle 60s before cooler air rushes in
late this afternoon from the southeast.

Strong thermal advection in association with a strengthening low
level jet is the main driver of rain and wind developing this
evening into tonight. The LLJ really ramps up towards and after 2z.
Guidance consensus has been fairly consistent in have gusty winds,
but with peak winds by and large falling below advisory criteria.
The question is if the inversion in the lower levels can break down
enough to get enough momentum transfer down to the surface to get 45
to 55 mph gusts. Based on forecast sounding / profiles and taking a
look at profile lapse rates, and applying seasonal climo have leaned
towards only smaller percentage of mixing down despite the fact that
the NAM and GFS continue to be bullish with 70 kt magnitude wind
down to and just below 2 kft. And the window of maximum or higher
mixing would likely be short in duration and most likely for a 1 to
2 hour window just before the cold front starts to pivot through
when perhaps we lose the easterly component to the southerly flow.
This would point towards 5 to 7z for southwestern sections including
southern portions of NYC, and 8-10z or thereabouts for the window to
see a few advisory level gusts for eastern coastal sections. For now
have most zones peaking at 40 to 45 mph gusts, with a few 50 mph
gusts possible in the pre-dawn hours and approaching dawn out east.

Rainfall amounts looks to be on the order of three quarters of an
inch, to one and one quarter inch for much of the area. Locally
higher amounts of one and a half to one and three quarters of an
inch are possible and more likely to occur across northern portions
of Southern CT. The HREF / HREF PMM is the basis of the rain
forecast with respect to QPF. See the hydrology section for more
details. There is some elevated instability tonight, thus have
included slight chance of thunder beginning this evening and
carrying through the first half of Friday morning. Temperatures on
the strong southerly flow will be well above normal with lows
primarily in the 50s, to near 60 in NE portions of New Jersey and
NYC.

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
The moderate to locally heavier rain should get mainly east of the
CWA by mid morning Friday. The winds will be rather gusty, but
decrease some from their peak earlier. For a 3 to 4 hour period the
winds relax some, but then pick up some towards and just after
midday. Gusts up to 35 mph are expected as heights lower and more
ideal mixing takes place as lower heights build across the area with
steeper lapse rates and a trough swings through. A strong SW flow
will then become more westerly Friday night and into Saturday.
Spokes of energy along with a series of surface troughs will
reinforce drier air at the surface and eventually cooler air into
the start of the weekend. Expect a low end chance to slight chance
of showers, mainly further north and northwest for Friday and Friday
night. The trough axis pivots through Friday evening, and this would
be the time period of higher probability for shower activity. Any
showers may contain brief gusty winds, but much of the time it
should remain dry Friday afternoon and into Saturday with more of a
classic inverted V profile. The winds will be more westerly on
Saturday with gusts once again to around 35 mph. The pressure
gradient will then weaken as low pressure gets well north into
Eastern Canada, so expect the winds to diminish late in the day
Saturday and Saturday evening. Temperatures will be a touch
above normal on Friday before the cooler air arrives, with
cooler temperatures being right around normal on Saturday.

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A trough over the region exits to the east Saturday night into
Sunday morning with the upper-level pattern becoming zonal on
Sunday. The zonal west to east flow helps advect in higher moisture,
leftovers from a weak low that moved into the Great Lakes. At the
same time, some models indicated mid-level energy being ejected
through our area from the trough as it rises into Canada and the
weak low over the Great Lakes. Not all models agree on this
solution, but odds are we should see some scattered showers as this
moves through on Sunday. Isolated thunderstorms are also possible as
there could be some elevated instability, weak as it may be.

The trough exits east Sunday night with a strong ridge building over
the northeastern US and Canada Monday and Tuesday. This will lead to
sunnier weather on Monday and temperatures warming into the mid-70s
to upper-60s, supported by warm air advection aloft. Its important
to note that not all models agree with the ridge building on Monday,
with some guidance not showing a building ridge until Tuesday.

The ridge remains in place on Tuesday, though a strong upper-level
jet develops aloft with a stalled/warm front placing itself over the
area from a low in the northern Great Plains/Western Great Lakes.
These will act together to increase cloud cover through the day on
Tuesday, which will keep high temperatures a few degrees cooler on
Tuesday compared to Monday, but still reaching the 70s. This front
may lead to rain chances Tuesday night into Wednesday.

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --A warm front passes through the area this afternoon, with a cold
front following Friday morning.

IFR continues for most the day with the exception of brief MVFR
conds during the first half of the afternoon. IFR to LIFR
returns tonight. Showers becoming more likely late this
afternoon through early Friday morning. There is a period where
thunder is possible late tonight into early Friday morning, but
confidence is too low in coverage and occurrence to add to the
TAF.

E/SE winds increase around 10 kt early this afternoon. Winds
then veer further SE and continue to increase with gusts 25-30kt
by sunset with gusts up to 40kt possible overnight. LLWS begins
tonight and peaks overnight and Friday morning.

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

Amendments likely, especially this afternoon with the potential
for cigs to improve early and then lower again. Low confidence
in any thunder, will likely be isolated across the area.

OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...

Friday: IFR cond with showers and S winds G25-30kt AM. MVFR
with chance of showers PM and SW winds G30-35kt.

Saturday: Chance of showers mainly NW of the NYC metros, mainly VFR.
W-NW winds G25-30kt.

Sunday: Mainly VFR. Chance of MVFR and showers in the afternoon.
SW-W winds G20-25kt.

Monday: VFR.

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

.MARINE...
A warm front slowly advances north this morning and it results
in areas of dense fog, thus a marine dense fog advisory is in
effect until 15z. A southeast flow begins to pick up towards
midday, and especially during the late afternoon when small
craft conditions develop from SW to NE across the waters into
this evening. SSE gales are then likely to develop during this
evening and spread NE across the waters late in the night. Seas
will build quickly tonight with 10 to 15 ft ocean seas by Friday
morning. Gales conditions should give way to small craft
conditions from west to east Friday afternoon and evening on a
SW wind. Small craft conditions will linger through Saturday
with a W wind with gusts mainly 25 to 30 kt. Sub-SCA conditions
are expected thereafter, except on the ocean waters where 4-6 ft
seas likely linger through Monday.

.HYDROLOGY...
A period of moderate to heavy rain is tonight and into a portion of
Friday morning for eastern sections. At this time the flooding risk
from rainfall is limited despite the fact that antecedent
conditions / soil moisture remains rather high. Due to the
progressive nature of the system it is likely that any flooding
would be more of the minor, nuisance and urban-poor drainage
variety. WPC maintains a marginal risk of excessive rainfall
across the majority of the CWA, with a slight risk into far
western portions of the area (mainly west of the Hudson River
into Orange County).

.TIDES/COASTAL FLOODING...
-- Changed Discussion --Strengthening SE-S flow with a storm system late today into Friday
morning will likely force more widespread minor to locally moderate
coastal flooding. With increasing SE gusty flow, waves will increase
in height, setting up a widespread minor coastal flood event for the
forecast area shorelines. Some localized moderate coastal flooding
is forecast, especially for some of the South Shore Bays. Advisories
remain in effect everywhere, except southern Nassau where a Coastal
Flood Watch has been issued as there has been a slight increase in
confidence for moderate benchmarks to be reached.

There was a slight upward trend in Stevens Institute NY HOPS
ensemble. Used a blend of ETSS, ESTOFS and Stevens guidance,
weighting Stevens 95th and Stevens 50th a bit more. This gave
widespread minor flooding, with several sites in southern Nassau
reaching moderate flood benchmarks. Elsewhere, only locally
minor flooding is expected, if at all.

The minor coastal flooding is also expected to occur along the
tidally fluctuating areas along rivers in Northeast NJ going into
eastern parts of Union, Essex and Bergen Counties. This is seen with
the NY HOPS ensemble of Stevens Institute for locations such as
Barge Marina at Carlstadt NJ and Hackensack River at Hackensack NJ,
which could possibly get to moderate flooding. Due to lower
confidence, kept these locations in minor coastal flooding within a
coastal flood advisory at this time.

While forecast surge guidance on average was giving less surge and
total water level values for eastern sections of the coast just
below to near the minor benchmark, manually added more surge there
to account for higher winds and waves. Therefore these eastern
sections have a coastal flood advisory as opposed to a coastal flood
statement.-- End Changed Discussion --

.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --CT...Coastal Flood Advisory from midnight tonight to 5 AM EDT
Friday for CTZ009-010.
Coastal Flood Advisory from 11 PM this evening to 4 AM EDT
Friday for CTZ011-012.
NY...Coastal Flood Advisory from midnight tonight to 5 AM EDT
Friday for NYZ071-073-078-176-177.
Coastal Flood Advisory from 9 PM this evening to 2 AM EDT
Friday for NYZ072-074-075.
Coastal Flood Advisory from 11 PM this evening to 6 AM EDT
Friday for NYZ079.
Coastal Flood Advisory from 11 PM this evening to 5 AM EDT
Friday for NYZ080-081.
Coastal Flood Advisory from 9 PM this evening to 3 AM EDT
Friday for NYZ178.
Coastal Flood Watch from 9 PM EDT this evening through late
tonight for NYZ179.
NJ...Coastal Flood Advisory from 9 PM this evening to 2 AM EDT
Friday for NJZ006-104-106-108.
MARINE...Dense Fog Advisory until 11 AM EDT this morning for ANZ331-332-
335-338-340-345-350-353-355.
Gale Warning from 8 PM this evening to 4 PM EDT Friday for
ANZ331-332-340-345.
Gale Warning from 6 PM this evening to noon EDT Friday for
ANZ335-338.
Gale Warning from 6 PM this evening to 6 PM EDT Friday for
ANZ350-353-355.-- End Changed Discussion --

SYNOPSIS...JE/BR
NEAR TERM...JE
SHORT TERM...JE
LONG TERM...BR
AVIATION...IRD
MARINE...JE/BR
HYDROLOGY...JE
TIDES/COASTAL FLOODING...