Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 290025
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
825 PM EDT Fri Apr 28 2017

.SYNOPSIS...
A series of weak fronts cross the region tonight into Saturday
night. High pressure will return briefly for Sunday. A warm
front will then approach from the south Sunday night, and lift
into or through the area on Monday, followed by a cold front
from the west Monday night into early Tuesday morning. Weak high
pressure will return for the rest of Tuesday into Wednesday. A
low pressure system will then approach on Thursday, and pass
nearby on Friday. Weak high pressure then builds in through
Wednesday. A frontal system approaches from the southwest
Thursday and moves along the coast through late week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Minor adjustments were made to the forecast database to reflect
the observed trends. Clouds were increased but exhibit these
are mainly cirrus. Lower and thicker clouds are expected later
tonight as the chances for showers and thunderstorms increase
ahead of the warm front. With coherent Showalter index forecast
agreement between different models with slightly negative
values, elevated instability is conveyed, and hence the
potential will be there for thunderstorms. The coherent
mesoscale reflectivity fields show higher reflectivity
forecast in the 09-12Z timeframe in the region. The forecast
precipitable waters increase to near 1.6 to 1.7 inches briefly
early Saturday morning with the convection so brief locally
heavy rain will be possible especially with any thunderstorms.

Through this evening high pressure will remain across the region
as Bermuda high pressure remains in the western Atlantic. This
keep a south to southwest flow across the area with increasing
dew points tonight. A warm front will be developing after 03Z
from low pressure across the central plains. There will be
increasing lift and instability mainly aloft late tonight and
into Saturday morning. In addition a weak vort will travel along
the developing warm front. This is expected to trigger showers
and a chance, or scattered embedded thunderstorms late tonight,
after 08Z.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
The front will remain in the area into early Saturday morning
and then dissipate as the Bermuda high builds back into the
area, leaving a warm and humid, summer like airmass in place.
Also, the vort moves quickly east of the region by 15Z, may be
sooner as depicted in some short term guidance. Afterward expect
area to remain dry, although both the NAM and GFS hint at some
precipitation heading close to the area late Saturday afternoon.
More likely is that maybe scattered showers develop on the
periphery of the high late in the day. Despite rain and clouds
early in the day, high temperatures expected to be close to
Friday highs, a couple of degrees lower, as sunshine develops
and with mixing to 900-850 MB. The boundary, cold front then
gets push south late Saturday night as high pressure builds to
the north.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Remarkably consistent trend to the long term, so changes to the
previous forecast have been minor at most, except perhaps for Sunday
into Monday. Temps have trended a little cooler for Sunday after the
back door cold frontal passage, with highs from the upper 50s to mid
60s, warmest west of the Hudson. Precip with the approaching warm
front looks to be on the light side, but do expect widespread low
clouds to develop, also some patchy fog late Sunday night into
Monday morning just ahead of the warm front. Depending on the
strength of a lobe of high pressure off to the east and the
potential for a weak wave of low pressure to develop along the
front, it may take some time for the front to lift north of the
area, especially across Long Island and southern CT, so there will
be a wide range of potential high temps on Monday. High temp
forecast is close to the 00Z ECMWF ensemble mean MOS, with 60s
across southern CT and most of Long Island, and 70s west of there.
That said, the high end ensemble numbers suggest lower 80s are
possible west of the Hudson, and widespread 70s farther east, if the
front lifts through by afternoon.

At any rate, a cold front should move through Monday night into
early Tuesday morning with showers and a few thunderstorms, followed
by dry wx for the rest of Tue into Wed, with temps running above
average especially on Tue, with upper 60s to mid 70s, then mid and
upper 60s on Wed.

As noted a couple of days back, chances for rain will increase late
this week as flow aloft becomes zonal at first, then more amplified
via a developing upper trough in the Central states. The resulting
deep layer SW flow in its advance should result in surface
cyclogenesis along a baroclinic zone over the southern Plains and
lower Mississippi Valley, with this low then moving up the coast
toward the area and tapping into Gulf and Atlantic moisture. This
has some potential to be a heavy rain maker on Friday if the
synoptic scale ingredients are in sync, but it is still too early to
know for certain.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
A weak cold front settles over the area tonight...with a wave of
pressure moving through early Saturday morning. The cold front
slowly sags south of the region late Saturday.

VFR conditions into this evening. By late tonight, an area of
showers will approach from the west, and should pass through from
8-14Z, west to east. Medium to high confidence in sparse
coverage of tstms...conveyed through a VCTS.

The other concern is potential for IFR/LIFR
stratus/fog...currently lurking offshore...working back into
KJFK/KISP/KGON overnight. Elsewhere MVFR or IFR conditions are
possible in fog and showers late tonight into Sat morning. Once
these showers move through by late Sat morning, VFR conditions
will return.

S winds lighten tonight, and eventually turn toward the W/SW by
late morning Saturday. Westerly gusts to 25-30 kt likely for
KLGA/KEWR/KTEB/KSWF Sat aft. South coastal terminals likely to
see winds backed to the SW...with gusts 20 to 25 kt in the
afternoon. Winds should eventually veer to wnw late Saturday.

     NY Metro Enhanced Aviation Weather Support...

Detailed information...including hourly TAF wind component fcsts
can be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: Medium to high confidence in sparse coverage
of tsra between 08z and 13z. IFR/LIFR stratus/fog possible for
morning push.

KLGA TAF Comments: Medium to high confidence in sparse coverage
of tsra between 08z and 13z. MVFR/IFR stratus/fog possible for
morning push.

KEWR TAF Comments: Medium to high confidence in sparse coverage
of tsra between 08z and 13z. MVFR/IFR stratus/fog possible for
morning push.

KTEB TAF Comments: Medium to high confidence in sparse coverage
of tsra between 08z and 13z. MVFR/IFR stratus/fog possible for
morning push.

KHPN TAF Comments: Medium to high confidence in sparse coverage
of tsra between 08z and 13z. MVFR/IFR stratus/fog possible for
morning push.

KISP TAF Comments: Medium confidence in sparse coverage of tsra
between 09z and 14z. IFR/LIFR stratus/fog possible for morning
push.

.OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...
.Saturday Night-Sunday...VFR...then MVFR cigs possible late
Sunday. Winds veering from NW to E/NE Sat night. E/SE gusts 15
to 20 kt Sun aft.
.Sunday night-Monday...MVFR or lower possible in showers and
fog.
.Monday night...MVFR in showers/possible thunderstorms. LLWS
possible.
.Tuesday-Wednesday...VFR.

&&

.MARINE...
Long period south to southeast swell of around 3-5 feet
continues on the ocean waters. The combination of wind wave and
swell was allowing for seas to fluctuate around 5 feet mainly
on the waters east of Fire Island Inlet. Seas and swell will be
slow to subside this evening into late tonight and could
fluctuate between 4 and 5 feet. The small craft advisory for
hazardous seas remains in effect until 06Z for the waters east
of Fire Island Inlet.

Winds and seas will then be below advisory levels until later
Saturday afternoon as a south to southwest flow strengthens and
seas build once again on the ocean waters. Then seas subside
Saturday evening as winds diminish.

With the current small craft advisory in effect will not issue
one for Saturday at this time.

Increasing easterly flow between a warm front approaching from the
south and high pressure off to the northeast could push ocean seas
up to 5 ft late day Sunday into Sunday evening.

Still high confidence in increasing S-SW flow pushing ocean seas
above 5 ft early next week, most likely by Mon night head of a cold
front, and lasting into at least Tue night if not Wed as moderate
post-frontal WSW flow continues. Could see gusts up to 25 kt there
late Mon night into Tue afternoon, with seas peaking at 5-7 ft Tue
morning.

&&

.HYDROLOGY...
No hydrologic impacts are expected through Thursday.

A low pressure system approaching from the southwest could
offer potential for heavy rain and hydrologic impact on Friday,
but it is too early to know for certain.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory for hazardous seas until 2 AM EDT
     Saturday for ANZ350-353.

&&

$$
SYNOPSIS...Goodman/MET
NEAR TERM...JM/MET
SHORT TERM...MET
LONG TERM...Goodman
AVIATION...NV
MARINE...Goodman/JM/MET
HYDROLOGY...Goodman/MET



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