000
FXUS61 KOKX 161547
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1147 AM EDT Fri Jun 16 2023
.SYNOPSIS...
A frontal system and associated low pressure pivots through today
and tonight, then stalls just to the northeast for the first half of
the weekend. Low pressure heads east Sunday as high pressure
builds in from the northwest through Monday night. Weak low
pressure remains south of the area Tuesday through Thursday with
high pressure anchored north of the region.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Made several changes with this update, mainly with POPs after
accounting for current trends with convection compared to
different CAMs reflectivity forecasts and also with
temperatures. Preferred the HRRR with regards to convection
forecast. Main change late afternoon into evening shifting the
likely to categorical POPs to across Long Island and Southern CT
and then decreasing the POPs to chance to the west. Next change
just having likely POPs out east across Twin Forks of Long
Island and SE CT tonight and mainly chance POPs for the rest of
the area for tonight.
Upper level trough approaches the region through this afternoon
with height falls increasing, increasing synoptic lift. The
trough axis moves across tonight with continued height falls. At
the surface, SE to S winds increase ahead of an approaching
area of low pressure from the DelMarva. The winds gradually
become lighter and more northerly tonight as the low passes
south of Long Island.
Bulk shear 0-6km above the ground increases to 35-40 kt but
instability will be limited. The forcing and instability will
increase the coverage of showers and thunderstorms, especially
across the southern half of the forecast region, Northeast NJ,
NYC, Long Island mid afternoon into early evening. Timing for
NYC, NE NJ appears to be mainly mid to late afternoon and for
Long Island late afternoon into early evening. Farther north,
thunderstorms could exhibit less coverage due to less
instability.
Some thunderstorms could be strong with gusty winds and small
hail with most severe thunderstorm activity potential south of
the forecast region.
The convection starts early this afternoon west of NYC but will
initially be sparse coverage and then increase in coverage as a
line moves in from the west towards the middle of this
afternoon. CAMs vary with their depiction of the coverage of
convection. Some such as the HRRR and NSSL WRF weaken convection
and do not have much convective coverage this afternoon across
the forecast region while other CAMs show a greater coverage of
convection in the area, mainly along NYC and Western Long
Island.
It appears the convective development is following where the
instability is greatest which will be south of Long Island through
this afternoon. Within the local region, instability will be more
limited, with surface CAPE less than 1000 J/kg. The instability is
lower farther north across much of the local forecast region because
of increasing clouds expected to spread eastward from a larger area
of showers currently moving across Eastern PA into Upstate NY. Also,
models are indicating a maxima of low level Theta-E near the
convective initiation area and translates this area of higher
low level Theta-E into Northern NJ and NYC by late this
afternoon and then further northeast across a greater part of
the forecast region for early this evening. Will make the chance
of thunderstorms, or scattered coverage of thunderstorms,
follow the progression of this forecast low level Theta-E.
Otherwise, max temperatures this afternoon will be mainly near
75 to 80 degrees with less vast range for lows tonight, upper
50s to lower 60s. Also, late tonight with lulls in rain shower
activity and moisture laden grounds as well as light winds, have
forecast patchy fog as well.-- End Changed Discussion --
&&
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
The upper level low will then pause and set up just to the northeast
off the area on Saturday. With a cold pool aloft along with cyclonic
curvature in the lower to mid levels the risk of showers and a few
thunderstorms will remain in place. The best forcing will lift just
north and northeast of the area. Thus look for a mostly cloudy and
unsettled day with periodic showers and a thunderstorm or two
rotating through. A few storms may bring heavy rainfall as WPC
has place the eastern 2/3rds of the area in a marginal risk of
excessive rainfall. Temperatures will continue to run below
average due to lots of cloud cover and a developing cooler NW
flow. Most daytime max temperatures will run in the upper 60s to
middle 70s.
For Saturday night as the upper level low begins to slowly progress
further northeast some clearing looks to gradually work in from the
southwest. Therefore closer to and after midnight some clearing may
set in from the SW. A brisk NW flow on the backside of the low
should keep it brisk with minimum temperatures mainly in the middle
and upper 50s across the interior, and lower 60s along much of the
coast and the NYC metro.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Ensemble means continue to depict mean troughing over the eastern
CONUS with a departing closed low to begin the period. Weak ridging
then builds in from the northern plains by the middle of next week
while another upper low meanders over the southeast through the end
of the week. The forecast has trended a bit drier, overall.
Continued near to below normal temperatures to start, but highs will
be on the increase by week`s end. The NBM was followed closely for
this update.
Sprawling high pressure begins to build over the northeast behind
the departing low pressure on Sunday. This high looks to remain
anchored over the region through midweek sliding offshore by the end
of the week. After any lingering clouds/showers across eastern
sections of the area head east early Sunday, drier air advects in
behind the system through the day, and with weak ridging aloft, the
day should be mostly dry. Monday looks to be mostly dry and
seasonable, as well, though a shortwave to the northeast will
provide the chance of an afternoon shower/thunderstorm, mainly for
CT and the Lower Hudson Valley.
The Tuesday - Thursday period looks mainly dry, with a chance of
scattered showers each day. The is region caught between the western
side of the upper low over eastern Canada and the eastern side of
the ridging to the northwest, allowing for some weak shortwaves to
move through the area under the northerly flow. So while widespread
rain/thunder is not expected in this timeframe, diurnally driven
precipitation is possible each afternoon.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
Low pressure approaches and passes near the terminals this
afternoon into Saturday.
Showers and thunderstorms develop this afternoon, 17-23Z from
west to east, with MVFR or lower at times. Heavy rain and gusty
winds are possible with any thunderstorm. Severe Thunderstorms
are possible south the NYC terminals through mid afternoon.
Timing of storms may be off by an hour or two.
Light and variable winds become southerly towards midday. Late
this afternoon, wind directions could get tricky in areas of
showers and storms before turning northeast into Saturday am and
eventually NW by midday Saturday.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Timing of showers and thunderstorms may be off by an hour or
two. Low confidence in developing fog/low stratus this evening
into the overnight.
OUTLOOK FOR 00Z SATURDAY THROUGH TUESDAY...
Friday night: continued threat of MVFR or lower with showers and
tstms.
Sat: VFR to start, then chcs for MVFR or lower in sct aftn shwrs and
tstms.
Sun: Mainly VFR. A slight chc for shwrs and isold tstms.
Mon-Tue: Slight chc of MVFR at times in shwrs. Otherwise VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A south to southeast flow takes shape today in advance of an
approaching frontal system and low pressure. The pressure gradient
will remain relatively weak with all wind gusts remaining below 20 kt
and seas only up to about 3 ft on the ocean today and heading into
the start of the weekend. The winds will switch to the NW during
Saturday and will increase slightly, but will still remain below
small craft criteria.
From Sunday through Tuesday, sub SCA levels are forecast with weak
departing low pressure Sunday, and weak high pressure building in
for Monday into Tuesday.
&&
.HYDROLOGY...
-- Changed Discussion --
WPC has placed the area in a marginal risk of excessive rainfall
for today, and primarily the eastern 2/3rds of the area on
Saturday. At this time a flooding threat from heavy rain
appears to be minimal, with a low threat primarily only for
urban and low lying locations. The threat would increase if
thunderstorm coverage is more widespread than anticipated over
the next 36 hours.
No hydrologic impacts are expected from Sunday through Thursday.-- End Changed Discussion --
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk of rip currents today and a low risk on
Saturday.
Minor coastal flood benchmarks are likely to be reached for the
western south shore back bays of Queens and Nassau for this
evening`s high tide, and potentially for Saturday evening as well.
Tidal departures will run around 1 to 1 1/2 ft, with some locations
having departures closer to 2 ft.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JE/DBR
NEAR TERM...JM
SHORT TERM...JE
LONG TERM...DBR
AVIATION...IRD
MARINE...JE/DBR
HYDROLOGY...JE/DBR
TIDES/COASTAL FLOODING...