000
FXUS61 KOKX 061659
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1259 PM EDT Thu Jul 6 2023
.SYNOPSIS...
High pressure will remain in control for another day. A weak
cold front approaches on Friday and stalls over or near the area
through the weekend. Weak low pressure may then move through
the region early next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Fog has been slow to dissipate over the immediate coast on the
South Fork of Long Island, but is slowly drifting east. High
temperatures have been lowered there as sunshine is still
expected, but after a slow start it will be hard to achieve the
previous forecast highs.
A few showers and thunderstorms popped up in the Lower Hudson
Valley and western Connecticut at 16z with the the help of a
moisture southerly flow lifting over terrain, but have since
dissipated. Chances remain low north and west of the NYC this
afternoon. Mid-level Lapse rates of less than 6C, weak shear,
and no real forcing will make for a difficult time to overcome a
mid level cap.
A shortwave ridge aloft will remain in control for one more day
before working east of the area by this evening. Associated
surface high pressure will be centered well offshore. This will
maintain a weak southerly flow across the region with very warm,
humid conditions to continue.
Based on highs Wednesday, have weighed in the warmer NBM 50th
percentile. The NBM deterministic has generally been close to
the 25th percentile. This will result in highs once again
in the upper 80s/lower 90s, except for the cooler south shore
and twin forks of LI.-- End Changed Discussion --
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
A digging upper trough across east central Canada into the upper
Midwest and Great Lakes states will allow for the airmass to
gradually destabilize heading into the weekend. A weak cold
front will approach late Friday into Saturday increasing chances
for showers/thunderstorms, but mainly north and west of the NYC
metro. In addition, an onshore flow will keep coastal areas
relatively stable, while inland locations will continue to
feature poor mid level lapse rates and weak shear. Thus, not
looking for any strong and/or severe convection during this
time. However, PWAT values get up to around 2 inches with a
weak steering flow Friday evening along and ahead of the
approaching cold front. WPC has placed the Lower Hudson Valley
and NE NJ in a marginal risk for excessive rainfall during this
time, meaning the flash flood is expected to be localized at
this time.
Coastal locations will also have the potential for low clouds
and fog each night. However, with water temperatures in the
lower to mid 70s at the offshore buoys, confidence on advection
fog is not high. Warm season fog outside of cooler water
sources (marine, river valleys, lakes, etc,) can be a challenge
at this time of year. Dew points will be around 70, so will
need to be aware of the potential.
Highs will be a bit cooler Fri and Sat with the onshore flow and
approach of the upper trough, mainly in the mid to upper 80s.
Overnights lows will struggle to get below 70.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
No significant changes to the long term. Generally followed the NBM.
The long term appears somewhat unsettled through the weekend as mean
mid and upper level troughing and attendant shortwaves impact the
area into early next week. Ensemble means advertise a closed upper
low over central Ontario slowly working east and weakening into mid
next week. This feature will send a series of shortwaves and frontal
systems through the region during the period providing chances of
locally heavy precipitation and thunderstorms each day. As has been
the case locally of late, it does not look like any one day will be
a complete "washout" precipitation-wise.
Deep southwesterly flow aloft continues this weekend. The Canadian
upper low looks to edge to the southeast on Sunday and another
frontal system thus approaches. The forcing aloft looks a bit better
than on Saturday with a shortwave rounding the base of the low.
BUFKIT soundings showing PWATs increasing to nearly or just over 2"
(which is near the max value for date per SPC sounding climo) by
Sunday afternoon, which would raise the heavy rainfall potential
with any showers/thunderstorms that do develop. NBM probabilities of
>1" in 6 hours is still relatively low, 5-15%, with the highest
values across the Lower Hudson Valley and SW CT, though the trend is
up a bit from previous NBM cycles. WPC has thus placed the
northwestern portions of the area in slight risk of excessive
rainfall on Sunday.
The frontal system then looks to slowly move south of the area late
Sunday into Monday. A weak surface low may then move northeast along
the frontal boundary Monday into Tuesday, keeping precipitation
chances in the forecast.
Given the pattern, high temperates will remain near or slightly
below normal for the period in the low to mid 80s.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Weak high pressure remains in place today.
VFR today. Sub-VFR conditions should develop under low stratus
and patchy fog tonight and into Friday morning. Slight chance
of showers and thunderstorms to the north and west of NYC
terminals in the afternoon and early evening. Probability not
high enough to include in TAFs, but best chance is for KSWF.
Light southerly to variable winds increase to 10 kt before
becoming light and variable again tonight into Friday.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Offshore fog should stay at the immediate coast. Timing of
lowering categories tonight may be off by a few hours.
OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
Friday-Saturday: Early MVFR/IFR Friday morning, otherwise mainly
VFR. Chance of showers. Chance of thunderstorms for NYC terminals
and to the north and west in the afternoon into early evening
Friday. Chance of thunderstorms for all terminals in the afternoon
into early evening Saturday.
Sunday and Monday: MVFR possible with a chance of showers. A chance
of thunderstorms, mainly afternoon into early evening.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Potential for areas of fog, especially for the eastern nearshore
and ocean waters in the coming nights will have to be watched.
Otherwise, conditions will remain below SCA levels through the
upcoming weekend due to a weak pressure gradient.
&&
.HYDROLOGY...
No widespread hydrologic issues are expected. However, there is
a localized flash flood threat Friday late afternoon/evening
across the Lower Hudson Valley and NE NJ as a weak cold front
approaches from the west.
A localized threat of nuisance/poor draining flooding is
possible on Sunday, mainly north and west of NYC, with any
stronger or slow moving thunderstorms.
&&
.TIDES/COASTAL FLOODING...
For today and Friday, there is a low risk of rip current
development for all ocean beaches. However, latest wavewatch
guidance does show a 2 ft 9-10s SE swell moving in late Friday
that could increase the rip current risk to moderate.
In terms of coastal flooding, astronomical tides associated with a
full moon will gradually lower through the week. Generally,
localized minor coastal flood impacts are on tap again for
tonight`s high tide cycle for southern Westchester, southern
Fairfield, southern Queens, and areas adjacent to Lower NY
Harbor, with more widespread minor flooding (up to 1 ft of
inundation) for Southern Nassau. The threat is expected to
diminish moving into Friday.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT
Friday for NYZ179.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DW/MW
NEAR TERM...JT/DW
SHORT TERM...DW
LONG TERM...DBR/MW
AVIATION...IRD
MARINE...DW/MW
HYDROLOGY...DW/MW
TIDES/COASTAL FLOODING...