451
FXUS61 KOKX 280602
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
202 AM EDT Wed Aug 28 2024
.SYNOPSIS...
High pressure moves offshore tonight with a cold front sliding
through on Wednesday. High pressure will then build down from the
north Thursday into Friday. A frontal system will affect the area
for the weekend, with Canadian high pressure building in for
early next week.
&&
.NEAR TERM /THROUGH TODAY/...
The forecast is on track with only minor changes needed.
After a clear start, clouds are predicted via NWP to move into
the region later at night, especially for the western half of
the area. The night is expected to be primarily dry, although a
vort induced shortwave (associated with convection across
Central NY/PA could fire up a few showers later at night into
early Wednesday morning across the area. It will be humid and
seasonably warm with not much of a temperature spread across the
region with dew point readings in the upper half of the 60s on
a light S to SW synoptic flow. Night time lows are expected to
range from the upper half of the 60s to the lower 70s.
For Wednesday things have changed from previous forecast
cycles. The CAMs do not look nearly as impressive with respect
to shower and convective activity. After looking at various
forecast cycles there is a warm layer at 5 to 12 kft which
assists in capping things some. It will take more effort to get
parcels to the level of free convection (LFC). Thus the CAMS are
hinting at reflectivity but have difficulty in getting any
meaningful convection to fire across the CWA. One could argue
that the NSSL, and NAM make the best attempt, and perhaps the
HRRR as well. The HRRR on most of its recent runs has suggested
that convection gets going just south of the CWA. After
collaboration with SPC, the region is now in mainly a marginal
risk of severe weather on Wednesday, with is a downgrade
previously from a slight risk. If a couple of storms do form,
they will be capable of some strong gusty winds, but this looks
like a low likelihood relatively speaking from earlier.
Regarding temperatures on Wednesday the cold front appears to
be getting a bit more of a quicker push to the SE. The upper
level disturbance also appears to get sheared in the guidance.
Thus there appears to be more of a westerly component to the
flow towards later morning into the early afternoon. This would
serve to mix out things a bit more and lead to slightly lower
dew point readings. Heat indices will likely range from the mid
to upper 90s, and technically this is a tad below heat advisory
criteria (the one day criteria). But it appears to be close
enough to at least leave the heat advisory up for now and
continue it for the same zones that were issued previously. In
any event, it is going to be hot and humid so keeping with the
same messaging in products.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/...
For Wednesday night the flow quickly goes northerly during the
late evening, and then northeast after 6z. Dew point readings
drop into the middle and upper 50s up north, and the lower and
middle 60s elsewhere, thus it begins to feel more comfortable
going into Thursday morning with low temperatures primarily
getting through the 60s.
A few showers post frontal may attempt to get into western
sections periodically late Wednesday night and during Thursday.
The lower levels dry out quite a lot, but cannot rule out a few
sprinkles of a quick shower mainly for western sections during
this timeframe. Otherwise expect partly to variably cloudy skies
and much more comfortable conditions with temperatures likely
getting to about 5 degrees below average for the day Thursday.
Daytime highs will be in the middle and upper 70s for the most
part.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Good model agreement in weak shortwave troughing over the
northeast US moving east Thu Night into Friday, with shortwave
upper ridging briefly building in Friday into Fri Night. Rest of
forecast period will be influenced by an expanding central
Canadian trough, centered around closed upper low spinning
through northern Ontario/Quebec Friday thru Monday. Troughing
will amplify across the NE Sat thru Mon as a couple of shortwave
troughs slide through the region. Model spread in shortwave
timing increases a bit towards the end of the period, but
overall fairly good agreement.
At the surface, Canadian high pressure centered over northern
New England Thu Night, gradually slides east through Friday
Night. The result will be a maritime Canadian airmass advecting
into the region on persistent ENE flow. Onshore flow under
subsidence/waa inversion aloft may result in stratus development
and a few showers particularly across western areas into Friday
morning, before deep layered ridging strengthens. Temps will
run slightly below seasonable.
Weak lead shortwave approaches Sat and crosses Sat night with
associated pre-frontal trough approaching Sat aft/eve, and crossing
Sat Night. Good moisture advection and warm rain process ahead of
the trough (PWATS +2 std), with weak/elevated instability. Combined
with strengthening synoptic lift, this should present the potential
for scattered to numerous showers and isolated tstm threat late
Sat/Sat eve, translating east Sat night. Temps moderating to near
seasonable on Saturday with increase humidity levels.
Main upper trough axis approaches Sun/Sun Night, with pre-frontal
trough sliding east and cold front approaching. Potential for
isolated to scattered showers/thunderstorm activity, but
considerable cloud cover and best moisture/llj axis potentially
moving east, could mute activity. Temps slightly above seasonable
with Tds in upper 60s/lower 70s.
Trough axis slides overhead Monday and east Monday Night, with cold
front passing east Sunday Night into Monday morning. Drying
conditions Monday on NW flow as Canadian high pressure builds from
the NW. Sct-bkn instability cu and a few showers possible,
particularly across interior Mon aft. Temps nears seasonable.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
An approaching cold front overnight will pass through during the
afternoon and early evening hours on Wednesday.
Mainly a VFR forecast. A few showers between 06Z-07Z at KSWF,
but not expecting any restrictions. The cold front is forecast
to move through the area largely dry, but cannot rule out an
isolated thunderstorm. The best chance at this time will be
across the NYC terminals.
Winds will be SW at 10 kt or less overnight, highest at the
coastaL terminals. Winds will then veer through the morning
ahead of the approaching cold front, becoming W to NW during
the late morning into the afternoon, increasing to 10-15kt
G20kt. There is a bit of uncertainty with the timing of the cold
front, especially for the terminals east of NYC, where winds
may remains W/SW for much of the day before becoming NW. Winds
will become more northerly Wednesday evening, diminishing 10 kt
or less.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
There is a low probability of a shower/thunderstorm Wednesday
afternoon and evening, but confidence is too low to include in
TAF at this time.
In addition, the timing of the cold frontal passage could vary
by 1-2 hours, mainly on the later side
OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...
Late Wednesday night: VFR.
Thursday: Mainly VFR. Slight chance of an afternoon/evening
showers/thunderstorm north and west of the NYC terminals.
Friday: VFR.
Saturday: Chance of showers, possible thunderstorms and MVFR or
lower.
Sunday: Mainly VFR. Chance of a shower/thunderstorm, mainly in the
afternoon and evening.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
A SW flow prevails through tonight with ocean seas up to 3 ft.
Ocean seas nudge up a bit closer to 4 ft for the eastern ocean
by Wednesday afternoon with a cold front approaching and moving
through the waters later in the day. There may be a brief period
of small craft gusts Wednesday afternoon for the eastern most
ocean water s. The winds do switch to the W on Wednesday, then
quickly to the NW, N, and NE through Wednesday night.
By early Thursday morning a period of marginal small craft wind
gusts are possible for the southern near shore and ocean waters
via a tightening NE flow. Small craft, or at least marginal
small craft conditions will remain possible for the ocean waters
through much of the day Thursday with gusts 20-25 kt and
easterly wind waves of 4-6 ft seas. Have leaned towards WNA
guidance over NWPS guidance based on historical performance
during warm season E/NE flow events.
Marginal SCA seas likely on the ocean Thursday night with 15g20kt
E/NE winds flow. Winds and seas gradually subside on Friday, with a
weak pressure gradient keeping all waters below SCA criteria Friday
night this weekend.
&&
.HYDROLOGY...
No hydrological impacts are anticipated during Wednesday with any
storms that do form being widely scattered to isolated, and will
also move along quickly. Any hydro impacts towards the weekend
towards Saturday appear minimal at this time.
&&
.TIDES/COASTAL FLOODING...
-- Changed Discussion --
There is a moderate risk of rip currents on Wednesday as southerly
wind waves build to 3 ft, combined with a lingering 1 ft se
swell. Moderate to high rip/longshore current risk (rip current
risk will be enhanced especially along jetties and groins)
Thursday with a strong E to W sweep of 2 to 4 ft surf.-- End Changed Discussion --
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
for NYZ069>075-176>178.
NJ...Heat Advisory from 11 AM this morning to 8 PM EDT this evening
for NJZ004-006-103>108.
MARINE...None.-- End Changed Discussion --
&&
$$
AVIATION...DW