000
FXUS61 KOKX 082201
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
601 PM EDT Fri Sep 8 2023
.SYNOPSIS...
A frontal boundary remains north and west of New York City
through the weekend. The front passes east of the area late
Monday. Another frontal system will likely pass by the end of the
week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
-- Changed Discussion --
Temperatures have cooled quite a bit across the region in
response to the showers and thunderstorms. Heat advisory was
cancelled early. Otherwise, slight modifications to POPs for
showers and thunderstorms were made to the forecast database to
better match up with radar reflectivity trends.
High pressure remains centered well offshore with a stationary
frontal boundary to the northwest of much of the region. It is
here, where there is enhanced low level convergence and moisture
pooling, and with a mid to upper level shortwave approaching,
there is more vertical forcing with the positive vorticity
advection.
Main story will be heavy showers and thunderstorms going into
this evening. There have been severe thunderstorms across parts
of the NYC, Northeast NJ and Lower Hudson Valley thus far this
afternoon. The potential for more severe thunderstorms will
continue into this evening across these same locations as well
as Nassau County NY and Southwest CT. There is a severe
thunderstorm watch in effect for these more western parts of the
region until 11PM this evening.
Thereafter, CAMs are showing less coverage of convection for
late evening before potentially another area of convection
moves across overnight. There is some uncertainty with the
timing and coverage of thunderstorms with larger variance in
convection forecast placement within the CAMs. There will be
less forcing and coverage will be more limited for this
convection with some mid level slight ridging behind the
shortwave.
Hence, POPs are mainly in the chance range overnight.
Otherwise, with light southerly winds and abundant cloud
coverage, lows tonight will be mostly in the lower 70s with
dewpoints also in the lower 70s. There will be some fog
development with the nearly saturated low level environment
overnight into early Saturday morning especially for those
locations that received heavier rainfall from earlier. Put in
patchy fog in the forecast.-- End Changed Discussion --
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
Not much change in synoptic pattern but there will be some mid
level ridging during the day Saturday with another trough
approaching Saturday night.
Daytime instability with increasing CAPE will provide an
environment conducive to thunderstorm development but the
strength of the thunderstorms will not be as strong or severe as
the previous day. Locations closest to the frontal boundary, to
the northwest of NYC have a marginal risk for severe
thunderstorms but this forcing will be more from the low levels
where there could be greater instability compared to other parts
of the region.
Overall, in terms of forcing, there will be less shear aloft
which will also lead to slower moving thunderstorms. See
hydrology section for more details. Chances for showers and
thunderstorms increase in the afternoon with areas becoming
likely for showers and thunderstorms near and northwest of NYC,
which are closer to the frontal boundary.
Abundant clouds and the showers and thunderstorms and onshore
flow will result in a relatively cooler but still very humid
day. Highs Saturday are in the low 80s for most locations with
some mid 80s for Northeast NJ. Dewpoints still in the lower 70s
with heat indices forecast in the upper 80s to lower 90s, below
heat advisory criteria.
The showers and thunderstorm chances continue into Saturday
night. Lows forecast will still be very mild in the upper 60s to
lower 70s with dewpoints in the same range. Fog will be possible
once again.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Chances for shwrs Sun and Mon with a humid airmass and energy
embedded in an upr lvl trof. Inland areas favored for pcpn with low
lvl speed convergence in onshore flow. Enough instability per the
NAM for some embedded tstms, so isold tstm coverage has been
included thru Mon.
The boundary is weak but is modeled to come thru Mon ngt. The flow
then quickly becomes onshore again as the winds respond to lowering
pres to the west. A closed h5 low is progged to be tracking thru the
upr Great Lakes at that point, reaching QC on Thu. This will produce
additional chances for pcpn thru the period. The boundary is progged
to clear the area by late in the week drying things out.
For the latest on Lee, please refer to the NHC.
&&
.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
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High pressure remains offshore as a cold front slowly approaches
through this weekend.
Mainly VFR is expected for the remainder of the evening, with
MVFR to IFR developing across eastern Long Island and southeast
CT this evening. Some lingering showers are possible over NYC
metro this evening, but thunderstorms have diminished. Thunderstorms
are still possible across Lower Hudson Vally and southern CT
this evening. A scattered shower or thunderstorm cannot be ruled
out overnight, but coverage too limited to include in TAF at
this time.
Stratus and fog are expected to develop overnight into early
Saturday morning with MVFR to IFR conditions. Some LIFR is
possible at KJFK east across Long Island and up into southeast
Connecticut. Conditions improve back to VFR mid to late morning
into the early afternoon. It should be noted that there are
timing uncertainties with lowering conditions this evening, and
then improvement Saturday morning.
A light south, or light and variable, flow will persist through the
forecast period.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
IFR conditions may develop at KJFK 01-03z, but more likely
overnight. LIFR conditions possible early Saturday morning at
KJFK.
Timing of MVFR-IFR at KLGA, KEWR, and KTEB late tonight/early
Saturday morning may be off by 1-3 hours.
Timing of improving conditions Saturday morning may be off by
1-3 hours.
Amendments likely for thunderstorm timing Saturday afternoon and
evening.
OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY...
Saturday through Sunday: Showers likely and possible thunderstorms
each afternoon and evening, particularly NYC and points N&W on Sat,
possibly more widespread Sunday. MVFR or lower conditions each night
and early morning are likely in stratus and fog.
Monday: Possible early morning MVFR/IFR conditions. Showers and
thunderstorms, more likely across the northern and western areas.
Tuesday: Slight chance of showers with MVFR possible.
Wednesday: Chance of showers and a slight chance of thunderstorms
with MVFR to IFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
With a weak pressure gradient in place, winds and seas will be
well below SCA thresholds through Saturday night.
Winds are progged to remain blw sca lvls Sun-Thu. Swell will build
Wed and beyond with sca seas likely. Seas may build to around 15 ft
by the end of the day Fri.
&&
.HYDROLOGY...
Showers and thunderstorms will have less shear Saturday into
Saturday night, resulting in slower translational speeds. With a
humid environment in place, heavy downpours will remain
possible. With multiple rounds of showers and thunderstorms,
there will be potential for minor flooding with a marginal risk
for flash flooding.
Slow moving shwrs and tstms could produce areas of mainly minor
flooding Sun and Mon. No widespread hydrologic impacts are expected
Tue-Fri.
&&
.TIDES/COASTAL FLOODING...
-- Changed Discussion --
A low risk of rip currents is forecast at the Atlantic Ocean
beaches this weekend with light winds under 10 kts and 2 to 3
ft waves.-- End Changed Discussion --
&&
.CLIMATE...
Daily Record High Minimum Temperatures...
Sep 8
Central Park..76(2015)
LaGuardia.....76(2015)
JFK...........73(1983)
Islip.........76(2015)
Newark........73(1999)
Bridgeport....74(2015)
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...None.
NJ...None.
MARINE...None.-- End Changed Discussion --
&&
$$
SYNOPSIS...JMC/JM
NEAR TERM...JM
SHORT TERM...JM
LONG TERM...JMC
AVIATION...BR/MET/DS
MARINE...JMC/JM
HYDROLOGY...JMC/JM
TIDES/COASTAL FLOODING...JM
CLIMATE...