506
FXUS61 KOKX 070202
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
1002 PM EDT Sun Oct 6 2024
.SYNOPSIS...
A cold front passes through the area mainly during the morning
hours Monday. High pressure moves in Monday night. A series of
weak cold fronts moves through the area midweek as an upper
level disturbance slides through the northeast U.S. Meanwhile, a
large Canadian high pressure system builds in west of the area
midweek and south of the area late in the week. Another cold
front may move through the area next weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
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Forecast on track, as vigorous northern stream shortwave over
western Ontario, and associated ULJ streak, will pivot into the
region towards daybreak Monday. High-res model in good agreement
with convective line across central PA/NY tonight weakening and
scattering as it races ahead of main shortwave forcing and into
a more stable airmass east of the Appalachians. As shortwave
approaches towards daybreak, with a 25-30kt llj advecting in a
+1.5-2 STD pwat airmass, marginal instability, and good moisture
convergence ahead/along the distinct cold front, likelihood for
the convective line to better organized across LI/CT Monday AM.
Locally heavy downpours and isolated thunder threat as well
with a marginally unstable sounding profile, also signaled in
the SPC HREF for thunder prob low.
Previous discussion...Cloud cover will increase tonight due to
the warm front and increasing moistening of the atmospheric
column. Overnight lows will be in the mid-50s to low-60s.
Breezier weather also sets in thanks an increasing pressure
gradient. An Ambrose jet may set up as well along the NJ coast
into NYC and western Long Island thanks to the passage of a warm
front and increasing southerly and south-southwesterly flow.
Gusts up to 20 kt will be possible across coastal locations as
the night progresses.
CAMs are in good agreement with the progression and timing of the
cold front tonight into tomorrow morning and its associated showers
and/or isolated thunderstorms.
As for the rain, expecting more precipitation and shower coverage
for the northern/eastern half of the area compared to the
lower/western half of the area. Many different factors are
hinting at decent forcing. Positive vorticity advection aloft
and located somewhat in the left exit region of a weak jet
streak. Other factors to consider include increasing dewpoints
in the low-60s being advected in from a 25-35 kt LLJ ahead of
the front, better forcing with said LLJ, PWATs peaking around
1.4-1.5" (which is around the 90% percentile per SPC`s Sounding
Climatology page, and warm air advection due to the passage of
the warm front.
Overall, impact from the showers should not be too concerning given
the quick progression of the cold front. Clouds clear and dry
weather returns with the passage of the cold front, and as a large
Canadian high builds toward the region Monday night.-- End Changed Discussion --
&&
.SHORT TERM /MONDAY NIGHT/...
Cool, crisp air is expected Monday night following the passage of
the cold front and as a large Canadian high begins to build toward
the region Monday night. With a strong northwest flow, cold air will
be advected in Monday night leading to lows in the mid-50s to mid-
40s.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Good model agreement on northern stream upper low over Quebec on
Tuesday, gradually sliding east into northern New England thru mid
week, before gradually lifting NE of the region Friday into
Saturday. Trend over the last 96 hours has been for the closed low
to remain a bit farther north of the region for the mid week period,
with a alter shorter duration of heart of cold core swinging
through. Thereafter, general agreement on flatter long wave
troughing remaining across the NE US for the weekend, but spread in
shortwave timing details.
Deep WNW flow continues to bring in a fall airmass through mid-week
(coolest of the early fall season so far) as high pressure gradually
builds towards the region, and a series of weak cold fronts/troughs
move through the area Tue Night and Wed Night, bringing heart of
cool airmass Thu. A slower and briefer incursion of cool air than
earlier runs had shown. Mainly dry conditions during this period,
but as southern periphery of upper low moves close with a few
embedded shortwaves rotating through sct (locally bkn) instability
cu likely, and even isolated instability shra/sprinkle activity late
Wed into Thu period as upper trough axis move through.
Highs Tue are likely to run slightly below seasonable in caa, and
down to several degrees below seasonable by Thu (Upper 50s to 60 F
interior, lower 60s to 65F city/coast) as heart of cool airmass
descends on the region. With 850 hpa T trending a bit higher over
last 24 hrs (low single digits), NBM deterministic and cooler NBM
50th percentile blend looks reasonable based on deep low-level
mixing profile.
Mixed low-levels should keep overnight lows Tue Night, Wed Night,
and Thu Night from bottoming out in most areas, but potential for
brief windows for radiational cooling across far outlying areas
which could have T`s dropping into the mid 30s, bringing a low
potential for frost.
NBM T spread increases for Friday into the weekend based on how
quickly upper trough lifts ne and depth of mean troughing, but
overall a moderating trend to seasonable signaled for Fri and then
potentially above the weekend seasonable as upper low (cold core)
likely lifts, height rise, and return flow develops. Timing
difference on potential cold frontal passage, with light rain shower
potential.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
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An approaching cold front will pass through the terminals during
the morning into early afternoon hours Monday.
VFR through the most of the night with MVFR conditions likely
in showers/isolated thunderstorms during the morning into early
afternoon Monday. VFR conditions WILL return about 2-3 hours
following the cold frontal passage.
Winds will be S/SSE around 10 kt at the coast tonight, but
lighter inland. There could even be a few gusts 15-20kt along
the coast due to a strengthening southerly low-level jet. Winds
veer to the NW behind the cold front at 10-15kt with gusts
around 20kt.
NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Gusts overnight may be more occasional. Best chance at KJFK.
Timing of wind shifts and changes in ceiling category may vary
by 1-2 hours.
Isolated thunderstorm possible in the morning. Confidence too
low at this time to mention in TAF.
OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
Monday Night: VFR. Winds NW 10-15g20kt first half of night.
Tuesday: VFR.
Wednesday and Thursday: VFR. Winds W-NW g15-20kt, mainly late
morning into the afternoon.
Friday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --
&&
.MARINE...
SE swells continues build to SCA levels tonight as long period
swells from Hurricane Kirk (see NHC for forecast details) build into
the waters. These long period swells peak at 5 to 6 feet
Monday, gradually subsiding below SCA late Monday night into
Tuesday morning. Also, southerly winds ahead of a cold front
likely briefly gust to near 25 kt on the ocean waters Monday
morning with the winds shifting to northwest with the cold front
passage. Then, Monday night northwest gusts again may near SCA
levels.
Long period swells likely subsiding below SCA Tuesday morning.
Generally sub-SCA W/NW gusts through midweek, with potential for
marginal SCA gusts over the ocean Wed Night into Thu AM in
wake of strongest cold frontal passage.
&&
.HYDROLOGY...
No hydrologic issues are expected throughout the forecast
period.
&&
.TIDES/COASTAL FLOODING...
5 to 7 ft surf is expected to cause scattered areas of beach
flooding and localized dune erosion during times of high tide
Monday morning in response to 5ft long period SE swells from
Hurricane Kirk (see NHC forecasts for forecast details).
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 8 AM EDT Tuesday for ANZ350-353-355.-- End Changed Discussion --
&&
$$
SYNOPSIS...BR/NV
NEAR TERM...BR/NV/DW
SHORT TERM...BR
LONG TERM...NV
AVIATION...DW
MARINE...BR/NV
HYDROLOGY...BR/NV
TIDES/COASTAL FLOODING...