000
FXUS61 KOKX 211434
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1034 AM EDT Thu Sep 21 2023
.SYNOPSIS...
High pressure continues to gradually build in from the west
today, then lifts to the north and east tonight into Friday
ahead of low pressure developing off the Southeast coast. This
area of low pressure will slowly work northward and impact the
area over the weekend, and possibly into early next week. Behind
it, high pressure reasserts itself as it builds south out of
Canada.
&&
.NEAR TERM /THROUGH TONIGHT/...
Forecast is on track this morning with some minor adjustments to
better capture recent observations. Previous discussion
follows.
Today remains largely a carbon copy of Wednesday. Surface high
pressure centered over upstate NY will build and shift northeastward
during the day. Dry conditions with dewpoints in the low to mid 50s
will prevail as weak northerly flow becomes northeast through the
day, as the high continues to move northeast.
Another decent radiational cooling night in store, as winds weaken
along with clear skies, with lows in the mid to upper 50s for urban
and coastal areas, and upper 40s across eastern Long Island and the
interior. Have followed a MAV/MET MOS blend for lows given the
typically better handle on these scenarios than the NBM.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
For Friday and onward, confidence continues to increase that a
coastal low pressure system with a southeast US origin will impact
the area.
There continues to be some model differences in the evolution of
this system, though there is agreement, generally, on the overall
pattern. A surface low deepens off the Carolina coast on Friday as
it heads northeast into the area this weekend. While there remains
some differences mainly now in just the track of this feature, a
general consensus that the surface low will track near the local
area seems more apparent with the latest runs. Thus, it appears more
likely that a wet, windy weekend is in store across the Tri State.
The ridging in that was in place over the northeast during the week
pushes further offshore by Friday evening. At the same time, a slow
moving upper/mid level low originating over the Carolinas pushes
slowly north and is somewhat impeded by the ridging in place over
the northeast. The deterministic guidance in general has shifted the
track of the surface low back to the west, notably the 00Z EC,
heading through eastern NC and VA by Saturday afternoon, and
northward through DelMarVa by early Sunday.
Increased easterly flow and precipitation onset looks to begin
locally by early to mid morning on Saturday, with most guidance
continuing to indicate an inverted trough feature associated with
the main sfc low. It`s the precip associated with this feature that
looks to give us a period of heavier rainfall Saturday morning into
Saturday afternoon, with higher amounts across Long Island and
coastal CT. The Global ensemble (GEFS, CMCE, ECE) means continue to
paint a widespread 1-2.25" Saturday into Sunday for the area. NBM
v4.1 probabilities of >2" over the 24 hours ending 12Z Sunday remain
similar to previous cycles, with a widespread 20-30% across Long
Island and CT. However, the NBM v4.1 probabilities of >1" in any 6
hour period still remains low, with only about 10% for the 6 hour
period ending 18Z Saturday for example, as a signal for periods of
heavier rainfall. Details should come into better view today with
additional high resolution/convective allowing guidance sources
available for that time horizon which will help better diagnose the
potential for locally heavy rainfall especially Saturday morning.
Depending on the surface features, flow could allow sustained winds
15-25 mph, occasionally gusting over 35 mph, especially along the
coast on Saturday.
As the surface low slowly works northeastward on Sunday, clouds and
showers will continue throughout the day.
Temperatures will remain on the cool side both Saturday and
Sunday given the cloud cover and rain, with highs in the 60s.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Did not make any too many significant changes in the long term and
stuck fairly close to the official forecast/NBM.
While forecast guidance comes into better agreement with the overall
pattern to end the weekend, there remain subtle differences to the
exact placement of the low and the timing of its exit. Overall,
thinking is the coastal low will remain in the vicinity of our local
area on Sunday. Will continue to carry chance POPs Sunday and early
Sunday night, with POPs gradually diminishing late Sunday night.
By Monday, the weakening low is forecast to slide offshore. Some
gradual drying out is likely Monday into Tuesday, with onshore flow
continuing as Canadian high pressure noses south, holding
temperatures down a bit below normal values through mid next week.
Another chance of rain comes Wednesday into Thursday, however
chances remain rather low at this point.
&&
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
High pressure remains over the terminals through the TAF period
with VFR conditions.
A north flow 5-10kt continues for the remainder of the morning
as winds slowly shift to more NE by afternoon at or around 10kt.
Some coastal terminals may have sea breeze influence late
afternoon that may allow winds to become more easterly. Can not
rule out a short period after 20z, where winds try to turn more
southerly at some of the coastal terminals. Have included this
in a tempo group. Winds become light and variable once again
tonight.
....NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments possible for wind direction changes at KJFK this
afternoon.
OUTLOOK FOR 15Z FRIDAY THROUGH MONDAY...
Friday: VFR.
Saturday and Sunday: MVFR or lower likely in rain. E gusts 20-30
kt, possibly up to 35 kt, strongest at coastal terminals to the
east. Strongest winds at this time look to be on Saturday.
Monday: Mainly VFR. MVFR possible in showers.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n900-- End Changed Discussion --
&&
.MARINE...
Gale Watch has been issues for the ocean waters for Saturday
into Saturday night.
Sub-SCA winds and waves are generally forecast through Friday. Ocean
seas will build to around 4ft today, and may for time touch 5 ft
in a long period ESE swells originating from Hurricane Nigel.
Marginal SCA conditions Friday afternoon as winds pick up, with
SCA conditions likely on all waters Saturday into Sunday as a
coastal low passes through the region. Gales are possible on the
ocean waters Saturday into early Sunday.
Winds may then remain above 25 kt on all waters through Sunday
afternoon before lowering. Elevated seas above 5 ft likely linger on
the ocean into Monday. Thereafter, sub SCA conditions expected on
all waters.
&&
.HYDROLOGY...
A widespread rainfall event appears likely this weekend, with 1-2
inches of rain possible in some areas. WPC has placed NYC and Long
Island in a marginal risk of excessive rainfall for Saturday.
Hydrologic impacts such as nuisance flooding will be possible
with locally heavy downpours, though confidence in rainfall
rates exceeding flash flood guidance remains low at this time.
No hydrologic impacts are expected thereafter.
&&
.TIDES/COASTAL FLOODING...
There is a high rip current risk for all Atlantic facing
beaches on Thursday and Friday with 3 to 4 ft swells and 12 to
14 sec periods. This should lead to elevated surf heights as
high as 6 feet, as well as the risk for dangerous rip current
development.
Rough surf, dangerous rip currents, and beach erosion are all
possible this weekend as the coastal storm meanders nearby.
In addition, multiple tidal cycles of minor coastal flooding
starting with Saturday afternoon/evening`s high tide,
potentially continuing into early next week, will be possible.
Localized moderate cannot be ruled out across the south shore
back bays of western LI.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Risk for Rip Currents through Friday evening for NYZ075-080-
081-178-179.
NJ...None.
MARINE...Gale Watch from Saturday morning through late Saturday night
for ANZ350-353-355.
&&
$$
SYNOPSIS...BC/DBR
NEAR TERM...DBR/DW
SHORT TERM...DBR
LONG TERM...BC
AVIATION...BR
MARINE...BC/DBR
HYDROLOGY...BC/DBR
TIDES/COASTAL FLOODING...