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fxus61 kokx 270939 
afdokx

Area forecast discussion
National Weather Service New York New York
539 am EDT Tue Jun 27 2017

Synopsis...
a cold frontal passage occurs tonight. A Bermuda high sets up
Wednesday night. Then a frontal system passes north of the
region Thursday through Friday night. A cold front approaches
Saturday and moves across Sunday into Sunday night. The front
may linger south of the region early next week with otherwise
weak high pressure returning.

&&

Near term /through tonight/...
upr lvl low shows up on stlt E of Detroit this mrng. The system
will continue to track ewd today, then drift newd tngt. The
associated cool front tracking across Ohio will reach the cwa tngt
and pass offshore by sunrise Wed. All of the models are in good
agreement with this soln.

Radar indicates shwrs and tstms still firing from sern PA to New Jersey.
Water vapor suggests the dynamics are sufficient for this to
continue thru the mrng and expand into the swrn portion of the
fcst area thru 12z. The NAM, GFS and European model (ecmwf) all support this
scenario.

After the first round of shwrs and embedded tstms this mrng,
lapse rates steepen as the h5 trof axis approaches, and with a
120kt jet streak passing thru, isold-sct shwrs and tstms are
fcst today before ending this eve as subsidence develops.

The nearly dry adiabatic lapse rates up to h85 indicate a
potential downburst scenario with the deepest convection. In
addition, around 1500 j/kg of SBCAPE progged by the NAM is
balanced by a brn around 35 and an el blw 30k ft could allow for
mini supercells. This would produce a hail threat, particularly
with any dry air intrusion abv h7 which the NAM predicts.

The limiting factor for tstm development this aftn, especially
the srn half of the cwa, is the amount of subsidence in the wake
of convection this mrng which could suppress later development.

Mainly clr in the wake of the upr trof tngt similar to the
current stlt over the Midwest.

Temps were a blend of guidance which was in good agreement.

There is a MDT risk for rip current development today.

&&

Short term /Wednesday/...
despite very steep low lvl lapse rates, subsidence should keep
the area dry. There could be some flat cumulus, however with
condensation pres deficits around 40, even this may be
difficult, especially away from any terrain enhancement. Despite
the cool airmass aloft, deep mixing will allow for highs to be
only a few degrees blw average. A blend of guidance was used for
this.

&&

Long term /Wednesday night through Monday/...
the jet lifts north of the region and stays north of the region
midweek going through much of the weekend. It starts to move farther
south into the region Sunday afternoon into Sunday night, before
lifting back north of the region early next week.

The mid and upper level flow transitions to more of a zonal flow mid
into late week and then transitions to more of a ridging pattern
going into the weekend. Shortwave approaches for second half of
weekend, presenting more of a trough pattern and SW flow aloft,
before returning to a quasi-zonal flow early next week.

High pressure moves off into the western Atlantic, building
Wednesday night, and then slowly drifting farther out to sea through
Thursday night. Meanwhile, a warm front moves north of the Great
Lakes and into northern New England Thursday into Thursday night.
There is a trailing cold front to the west that looks to weaken
Thursday night before moving northward as a warm front Friday into
Friday night. A cold front from the west approaches Saturday and
moves across Sunday into Sunday night. Possibly this could get
delayed as shown by the ECMWF, hence the longer time window
stated for its passage.

The frontal boundary of the weakening cold front Thursday night into
Friday is forecast to be close enough to warrant a chance of a
shower or thunderstorm. The chance continues into Friday night. The
next chance of showers and thunderstorms will be this weekend.
Another chance but only slight chance of showers and thunderstorms
is forecast for early next week with frontal boundary possibly
lingering not too far away to the south of the region.

Temperatures start off near normal Wednesday night and Thursday but
then trend warmer for the rest of the forecast period. It will be
getting warmer and more humid. The temperatures will average about 3-
5 degrees above normal.

&&

Aviation /10z Tuesday through Saturday/...
mainly VFR through the taf period. A trough of low pressure
passes across the terminals late this afternoon and evening.

Light winds should continue to back to the west by 12z at city
terminals, then gradually become southerly at 10 kt or less.
Winds veer to the SW by late afternoon and evening, 10-15 kt,
then to the west-west-northwest overnight around 10 kt.

Showers early this morning with brief reduced visibility to MVFR,
10-11z over NYC terminals, and 10-13z Long Island and southern
Connecticut terminals. A shower/thunderstorm is also possible
this afternoon.

... Metro enhanced aviation weather support...

Detailed information, including hourly taf wind component forecasts,
can be found at: http:/www.Weather.Gov/zny/n90

Kjfk taf comments: brief MVFR visibilities in showers through
11z. Winds should back to the west around 12z, and then to the S
around 15z. An occasional gust 18-20 kt possible in the
afternoon.

Klga taf comments: brief MVFR visibilities in showers through
11z. Winds should back to the west around 12z, and then to the S
around 15z. An occasional gust 18-20 kt possible in the
afternoon.

Kewr taf comments: brief MVFR visibilities in showers through
11z. Wind direction should gradually back to the
west-west-northwest by 12z, then to the south-southwest-SW through the afternoon.

The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kteb taf comments: brief MVFR visibilities in showers through
11z. Gusts this afternoon may end up occasional.

Khpn taf comments: brief MVFR visibilities in showers through
11z. An occasional gust 16-19 kt possible this
afternoon.

Kisp taf comments: brief MVFR visibilities in showers through
11z-13z. An occasional gust 16-19 kt possible this
afternoon.

Outlook for 06z Wednesday through Saturday...
Tuesday night-Wednesday...VFR.
Thursday...VFR. Chance of a late day shower/thunderstorm.
Friday and Saturday...MVFR or lower possible in showers and
thunderstorms.

&&

Marine...
winds and seas are progged to remain blw sca lvls thru Wed.

Sub Small Craft Advisory conditions are expected Wednesday night. Then Small Craft Advisory becomes
more probable Thursday through Friday night for the ocean with seas
reaching between 5-7 ft for much of the time. Wind gusts reach 25-30
kt much of the timeframe as well. Also during Thursday and Thursday
night, widespread for just about all waters, higher wind gusts near
25kt are forecast, with hence probable Small Craft Advisory conditions for all
waters. Ocean seas are forecast to linger in Small Craft Advisory range Saturday with
waves near 5 ft particularly east of Fire Island Inlet. Much of the
remainder of the weekend will have sub Small Craft Advisory conditions forecast.

&&

Hydrology...
no hydrologic impacts expected through the beginning of next
week.

&&

Tides/coastal flooding...
astronomical tides are still running high with a low chance of
any minor coastal flooding across the South Shore back bays of
Nassau County with the high tide cycle tngt. The water levels
would only be expected to touch the minor benchmarks at just a
couple of gages at most so no statement has been issued.

&&

Equipment...
observations from kfrg (farmingdale, ny) are not available.
Observations from khpn (white plains ny) and khvn (new Haven ct)
are being disseminated through backup methods. All is due to
an FAA communication line outage. Return to service time is
unknown.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...none.

&&

$$
Synopsis...jmc/jm
near term...jmc
short term...jmc
long term...jm

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