000
FXUS61 KOKX 090547
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1247 AM EST Sat Mar 9 2024
.SYNOPSIS...
High pressure late tonight gives way to a low pressure system
over the weekend. Strong low pressure will slowly exit the area,
moving through northern New England Sunday night. Meanwhile, high
pressure will build in from the west, likely moving across the
area on Wednesday. A frontal system will then potentially bring
unsettled weather for the end of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Small positive adjustments were made to temperatures and cloud
coverage. Overall, the forecast remains mainly on track.
High clouds continue to appear in latest IR satellite imagery
moving into the region from the west. Cloudy sky conditions are
expected for the rest of tonight for the entire forecast area.
Clouds lower and thicken late tonight as high pressure exits to
the east and a storm system approaches from the west.
Lows in outlying areas and within some interior areas were
increased several degrees compared to previous forecast.
Expansive clouds will limit the radiational cooling. The range
of lows forecast is from the lower 30s to lower 40s.
&&
.SHORT TERM /SUNDAY/...
A broad area of low pressure approaches on Saturday. While one
circulation center weakens as it heads NE into Quebec, a secondary
center deepens as it moves through the Mid-Atlantic. This will pass
through the forecast area late Saturday night/early Sunday morning,
then continue NE through New England during the rest of Sunday.
Rain spreads eastward through the forecast area Saturday afternoon
into evening. The rain could be briefly heavy at times starting late
in the evening as deeper moisture and deeper lift (low level jet and
left exit region of an upper jet streak) pass through. Additionally,
some elevated CAPE and marginally unstable mid-level lapse rates may
be present at this point, so there may be a convective element with
this as well - adding to the threat of a heavy downpour. Have added
a slight chance of thunder to the forecast. Given current flash
flood guidance, what was observed during the rain event couple of
days ago, and expected rain amounts, anticipating primarily minor
flooding impacts wherever flooding occurs. However, will go with a
flood watch over NE NJ and Rockland County where rain amounts could
be the highest and where conditions are most sensitive. See the
hydrology section below for more details. The steady rain will
likely end by daybreak Sunday in most spots. With an upper
low/cyclonic flow aloft lagging behind the surface low and
sufficient mid-level present, afternoon showers will be possible.
Snow showers could mix in late in the day NW of the city as freezing
level heights lower.
As for winds during this period, it still appears that the entire
area remains below advisory level thresholds before winds increase
further Sunday night. 925mb winds of 65-75kt anticipated over the
eastern zones late Saturday night, but with a strong low level
inversion, not so confident that 40kt+ gusts would mix down to the
surface even in heavier downpours. If this were to occur, it would
mostly likely happen over Long Island and SE CT. Then after a lull
in the winds with the low center passing through, winds pick up out
of the west late morning Sunday into the afternoon. Deep mixing with
winds at the top of the mixed layer perhaps getting into the 40-50kt
range over the western zones towards the end of the day might be
able to produce a gust or two to advisory levels. Being at the end
of the 4th period, it`s still too early for any advisory
consideration, and better chances for 40kt+ winds to occur start
Sunday night.
High temperatures for both Saturday and Sunday mostly in the upper
40s to around 50.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
By the start of the Sunday night period, the strong surface low that
will bring unsettled weather earlier in the weekend will be centered
over northern New England and slowly departing the area. By that
time, the area will be mostly dry, with just some lingering slight
chances of snow or snow/rain showers as the upper low moves
overhead, mainly for the northern half of the area. No accumulation
is expected.
As the strong surface low pulls away, high pressure starts to build
in from the west and the pressure gradient increases. Strong winds
are possible across the whole area on Monday. Deep mixing can be
seen in model soundings, with both the 12z NAM and GFS showing 45 to
50 kt at the top of the mixed layer. Forecast winds and wind gusts
have bumped up slightly, with much of the area right around Wind
Advisory criteria (sustained 31-39 mph, gusts 46-57 mph) late Monday
morning through the early evening.
The rest of the week will feature mainly quiet and dry conditions,
with a warming trend. A ridge builds over the eastern CONUS aloft as
high pressure remains in control at the surface. Highs Tuesday will
be in the 50s and by Friday they will be in the mid 50s to upper
60s. A frontal system does approach late week and could bring
unsettled weather to the area. For now, stuck close to the NBM
during that time period as there is quite a bit of spread among the
deterministic guidance. This gives slight chance PoPs Friday morning
increasing to chance PoPs by the afternoon. This would be an all
plain rain event.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
High pressure continues to move offshore with low pressure
approaching from the south and west late Saturday.
With the development of stratus overnight going into early Saturday,
MVFR conditions will become more widespread. Rain ahead of the
low starts Saturday mid to late afternoon west to east. IFR will
be possible at times Saturday, becoming more likely at night.
Rain Saturday night could become heavy at times. There is a
slight chance of thunderstorms for late evening.
Winds will become generally SE near 5-8 kt overnight. Winds
become more easterly Saturday and remain generally near 5-10 kt
for Saturday morning before picking up during the afternoon.
Winds increase to 10-15 kt range in the afternoon and then to
15-20 kt going into early evening. Gusts will become more likely
Saturday afternoon up to 20 kt, but around 25 kt going into
early evening. LLWS arrives towards late evening with SE winds
near 45-50 kt for most coastal terminals.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments likely to refine timing of MVFR, IFR and the rain
which could be a few hours off compared to TAF. There could be
fluctuation between MVFR and IFR throughout the day on Saturday.
OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY...
Late Saturday night: MVFR to IFR with rain. Localized Sub-IFR
possible at times. SE winds near 15-20 kt with gusts 25-30 kt,
becoming more northerly to westerly late into early Sunday AM
10-15 kt with gusts near 20 kt. LLWS SE winds 45-50 kt at 2kft
overnight. A slight chance of thunderstorms.
Sunday: MVFR early, then VFR by afternoon, except at KGON which
could be IFR early, then become MVFR later in the morning and
VFR by afternoon. SW winds 15-20G25kt early, becoming W
20-25G30-35 kt by afternoon. Rain showers possible, especially
near KGON and KSWF.
Sunday night: MVFR possible. Rain and snow showers possible Sunday
night for KHPN, KSWF and CT terminals. Otherwise, VFR. W winds 15-
20G25-30kt.
Monday: VFR. NW winds 20-25 kt with gusts near 35-40 kt.
Monday night: VFR. NW winds near 20 kt in the evening
with gusts up to 25-30 kt, eventually decreasing to 10-15 kt
with gusts 20-25kt late.
Tuesday: VFR. NW winds 10-15G20kt.
Tuesday night and Wednesday: VFR.
Detailed information, including hourly TAF wind component
forecasts, can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
Expecting ocean waves to hover around 4-5 feet through tonight due
to swell. There could be an extended period during later tonight
into Saturday morning where prevailing wave heights are below 5ft,
however not enough confidence to shorten the SCA at this time,
especially with the expectation of seas building back up during
Saturday afternoon as onshore winds increase. A gale watch has been
extended in time and is now up for all waters Saturday night through
Sunday night as a strengthening low pressure system passes through
during Saturday night and after a lull Sunday morning, westerly
winds ramp up Saturday afternoon and night as the pressure gradient
tightens.
Gale conditions will likely continue on all waters Monday
through the first half of Monday night. Gusts look to peak
Monday afternoon, with widespread 40 kt gusts, and 40 to 45 on
the ocean waters. Waves will be 9 to 11 feet on the ocean waters
Sunday night through the first half of Monday night, before
lowering. Waves also look to reach 5 ft across the LI Sound.
Gusts lower Monday night, but could remain around Small Craft
Advisory criteria through Tuesday. Thereafter, winds and waves
look to remain below SCA criteria, with the next potential being
with a frontal system at the end of next week.
&&
.HYDROLOGY...
Around an inch to 2 inches of rain is expected to fall Saturday
afternoon through Saturday night. The higher amounts are expected to
be north and west of NYC. There will be the chance of flash
flooding, primarily nearby smaller rivers and streams across NE NJ
into Rockland County due to antecedent wet soils and the anticipated
rain totals. The heaviest rainfall is expected late Saturday evening
into the early morning hours of Sunday. Otherwise, mainly minor/poor
drainage flooding will be possible Saturday night.
There are no hydrologic concerns Sunday night through next week.
&&
.TIDES/COASTAL FLOODING...
Water levels will be on the increase going into this weekend.
Statements and advisories are up for the high tide cycles
through Sat morning as water levels approach or exceed minor
thresholds.
Coastal flood watches remain for Sat night for the western Sound,
and for Sat night into Sunday morning for the south shore of Long
Island and Jamaica Bay. SE winds ramping up to gale force Sat
evening should result in tide departures of about 2.5 to 3 ft in
the western Sound and along the south shore of western Long Island
Sat evening per 2:1 blend of NYHOPS 50th and 95th percentile,
with water levels likely reaching moderate thresholds in the watch
area, with widespread minor flooding elsewhere.
As winds shift SW-W Sunday morning higher water levels, with
surge up to 2.5 ft on top of higher astronomical tides, should
lead to another round of minor to moderate flooding. Higher
surge is likely to be pushed eastward into the Great South Bay
and Jamaica Bay as has occurred with a few other events this
winter, with moderate flooding expected there, and at least
minor flooding elsewhere. Blend of Stevens NYHOPS 50th/95th
percentiles and the PETSS 50th percentile (leaning toward PETSS
numbers where higher along the Great South Bay) captures this
scenario.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...Coastal Flood Advisory from 9 AM this morning to noon EST
today for CTZ009.
Coastal Flood Watch from this evening through late tonight for
CTZ009.
NY...Coastal Flood Advisory from 9 AM this morning to noon EST
today for NYZ071.
Coastal Flood Watch from this evening through late tonight for
NYZ071-073-078-176-177.
Flood Watch from this evening through Sunday morning for
NYZ069.
Coastal Flood Watch from this evening through Sunday afternoon
for NYZ080-178-179.
Coastal Flood Watch from Sunday morning through Sunday
afternoon for NYZ081.
Coastal Flood Advisory from 5 AM to 9 AM EST this morning for
NYZ179.
NJ...Flood Watch from this evening through Sunday morning for
NJZ002-004-006-103>108.
MARINE...Gale Watch from this evening through late Sunday night for
ANZ331-332-335-338-340-345-350-353-355.
Small Craft Advisory until 6 PM EST this evening for ANZ350-
353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...JC/JT
NEAR TERM...JC/JM/JT
SHORT TERM...JC
LONG TERM...JT
AVIATION...JM
MARINE...JC/JT
HYDROLOGY...JC/JT
TIDES/COASTAL FLOODING...BG