000
FXUS61 KOKX 182129
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
529 PM EDT Wed Oct 18 2023
.SYNOPSIS...
High pressure remains in control through Thursday. A frontal
system approaches Thursday night and impacts the region Friday.
A secondary low develops along the Delmarva Friday night and
deepens through Saturday night while tracking to the northeast.
The low departs to the northeast Sunday as high pressure builds
in from the west and settles over the region early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
Minor adjustments have been made to the cloud cover and chance
for precipitation forecasts. Otherwise, the forecast remains on
track. Main forecast challenge for this evening remains to be
the amount of cloud cover. Subsidence inversion remains in place
between 7-10 kft. Moisture continues to be trapped beneath the
inversion and there is some weak instability. This has led to
mostly cloudy conditions throughout the area this afternoon,
which continues this evening. There have also been a few showers
that developed along the convergence of the sea breeze in the
afternoon. Will continue to mention a slight chance for showers
near the eastern coasts through 00z. Model soundings and time-
height cross sections indicate the moisture begins to
decrease/thin overnight. Lingering middle level shortwave energy
also departs to the east tonight, which should help limit lift
for cloud cover. Have slowed down the timing of the diminishing
clouds until mainly after 03z and it could remain mostly cloudy
inland until early Thursday morning.
Otherwise, surface high pressure will remain over the eastern
seaboard tonight. Ridging will begin to build aloft towards day
break Thursday. Lows should fall into the middle 40s inland and
upper 40s and low 50s elsewhere. If cloud cover hangs on longer
than anticipated, lows may need to be nudged upwards a degree
or two.-- End Changed Discussion --
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
A progressive ridge moves across the northeast on Thursday in
response to an amplifying trough over the central states. The
ridge axis along with the associated surface high will push
offshore late Thursday into Thursday as the trough approaches.
Associated with the trough will be a frontal system. Any precip
with the system likely holds off until early Friday morning.
A lingering subsidence inversion looks to remain in place on
Thursday, but forecast soundings indicate less moisture. Mostly
sunny conditions are expected Thursday morning before middle and
high level clouds begin to increase from west to east ahead of the
trough. Highs will be a few degrees above normal for this time of
year in the 60s.
Clouds continue increasing Thursday night. Models indicate a weak
wave of low pressure developing off the Carolinas/Middle Atlantic
late Thursday night. Showers with the wave may begin to approach
Long Island towards day break Friday. Have continued to indicate a
low chance PoP to account for this potential. Lows will be milder
in the lower and middle 50s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Friday starts off with a deep upper/mid-level trough to the west
that continues to deepen as it tracks east over the region into
Sunday. At the surface a low-pressure system tracks over the Great
Lakes on Friday with its associated frontal system. At the same
time, a surface low will likely develop off the east coast or near
us as it tracks northeast, departing on Sunday after a cold frontal
passage Saturday morning/midday.
Impacts from this system are still low confidence as the latest
12Z model guidance have different solutions. The GFS has the
coastal low developing over us and moving northeast while the
NAM has the coastal low developing off of the NC coast and
staying mostly offshore as it tracks up the east coast Friday
into Saturday. The GDPS is somewhere in the middle of these two
solutions. Either way, widespread rainfall is likely on Friday
into early Saturday with much of it being light to moderate, at
times. PWATs look to be 1.1- 1.3" (SPC sounding climatology 90th
percentile is 1.28") for the event with warm air advection from
a strong 20-30kt LLJ at 925mb from SW and SE flow as the
coastal system develops to the south and passes to the NE. The
NAM has a more potent system developing with stronger warm air
advection and MUCAPE 1000-1500 J/kg over the ocean and eastern
areas with stronger frontogenesis as it tracks over the area.
The ECMWF also develops a more potent low and similar track. I
have left the possibility of isolated thunderstorms for eastern
areas late Friday-early Saturday for this possibility. Some
models depict us in the right entrance and/or left exit region
between two jet streaks which should aid in widespread
precipitation. For now, QPF totals early Friday through Saturday
are 0.75-1", limiting any risk for flooding as this will fall
over a prolonged period of time.
A cold front is timed for early/midday Saturday which will bring
in a strong WNW to NW flow with wind gusts 25-30 mph late
Saturday into Sunday. Some eastern areas of Long Island could
gust up to 35 mph. Some lingering light precipitation is still
possible for northern interior areas late Saturday to early
Sunday if the low is slow to depart, but should remain isolated
as the coastal low moves further up New England. A large widened
trough remains aloft on Sunday leaving lingering cloud cover
and allowing cooler air to filter in.
Next week, ridging builds aloft as surface high pressure sets
in with it. As the pressure gradient weakens Monday into
Tuesday, winds will become light, particularly overnight, with
clearing skies. This along with cold air advection continuing,
temperatures could be in the low-40s with mid/low-30s possible
for interior areas. With the recent rain, soil moisture will be
higher, allowing for the development for areas of frost in the
interior. Highs should remain at between 50 and 60 Sunday
through Tuesday.
&&
.AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
High pressure remains overhead through this evening, shifting
offshore Thursday. VFR through the forecast period.
Flow turns southerly into late afternoon with speeds under 10 kt.
Brief MVFR cigs possible at KISP and KGON into early evening with
widely scattered showers. Winds lighten and become more SW this
evening at the NYC terminals, and lgt and vrb at the outlying
terminals. Not out of the question low stratus develops along the
coast toward Thursday morning, though confidence in occurrence is
low. Flow becomes S or SSE on Friday, with speeds around 10 kt.
....NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of wind shifts may be off by an hour or two.
Low chance of brief MVFR cig/vsby at KJFK Fri AM.
OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
Thursday Afternoon: VFR.
Friday through Saturday: MVFR/IFR with showers.
Sunday: MVFR early, becoming VFR. W to NW wind gusts 25-30 kt.
Monday: VFR. Gusty NW flow.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
A weak pressure gradient tonight through Thursday night will
lead to winds and seas below SCA levels.
SCA conditions are to start in the oceans 12Z Saturday with 5 ft
waves building to 8ft by 12Z Sunday. They will then gradually
weaken over the ocean until 12Z Monday. Gusts over the ocean
will also reach 25 kts 18Z Saturday, possibly reaching up to
35kts (marginally within gale criteria) 21Z Sunday. They will
drop below 25 kts after 12Z Monday as the pressure gradient
weakens and high pressure builds.
The window for SCA conditions is shorter for LI sound, bays and
harbors with waves expected to remain below 5 ft. WInds will reach
25-30 kts overnight Saturday and remain in place until early
Monday.
&&
.HYDROLOGY...
Potential for minor flooding Friday into Saturday. Otherwise no
other hydro problems expected.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BR/DS
NEAR TERM...BR/DS
SHORT TERM...DS
LONG TERM...BR
AVIATION...MW
MARINE...BR/DS
HYDROLOGY...BR/DS