Area Forecast Discussion
Issued by NWS Upton, NY

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290
FXUS61 KOKX 161710
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
110 PM EDT Thu Aug 16 2018

.SYNOPSIS...
Weak high pressure remains south of the area today as a
backdoor front approaches tonight and lifts back to the north
Friday. A cold frontal passage will move across the area on
Saturday. High pressure builds across the area Monday. A
frontal system may bring active weather late Tuesday and
Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Made minor adjustments to temperatures and dewpoints with the
afternoon update to reflect current weather conditions.
Otherwise, forecast still on track.

Ridge in place today and associated subsidence will result in
partly to mostly sunny conditions. Westerly wind flow will allow
for warm to hot temperatures across the entire region, even
coastal locations will warm well into the 80s to near 90.

The westerly flow however will mix out dew points, keeping
humidity levels down somewhat. As such, will maintain the heat
advisory for the metropolitan area where temperatures remain
warmer in the lower to middle 90s.

Any isolated showers or thunderstorms should remain to our
west.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Upper ridge slides to the east as upstream shortwave slowly
approaches this time frame. At the sfc, a backdoor cold front
should sag south across portions of the area, mainly SE CT and
perhaps the twin forks of Long Island. Partly cloudy skies are
anticipated, and temperatures will remain quite warm. Lows will
range from the upper 60s to the upper 70s in NYC.

On Friday, clouds will be on the increase, and shower and
thunderstorm chances will increase, mainly from west to east.
Although a few thunderstorms may develop just north of the area
along the weakening back door front that washes out, or lifts
to the north as a warm front.

Feel the bulk of the thunderstorm activity holds off until late
in the day, mainly across western locations. With increasing
clouds, temps warm, but not quite as high, peaking around 90.
However, increasing southerly flow ahead of a prefrontal trough
will allow dew points to rise into the 70s. This will create
heat indices in the lower to mid 90s across the advisory area.
Will thus maintain the heat advisory for the same locations.

There will likely be a moderate risk for rip currents on Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
A cluster of tstms associated with a prefrontal trof are expected
to roll across the area Fri ngt. It looks like the main challenge
will be whether the forcing from ongoing convection along with the
trof will be sufficient to keep the tstms robust as they encounter
increasing cin. The NAM suggests the answer is yes, and based on the
model`s recent track record with tstms recently, this soln has been
accepted. Some svr activity cannot be ruled out with strong sly bl
flow, llvl veering and cape over 2000. Progged lcls are blw 1000 ft
as well. There should be a window Sat mrng with no activity before
the next round of tstms with the fropa. Amount of convective debris
will have an impact on destabilization, so if there is much less
convection Fri ngt than expected, the svr threat could be a bit
better on Sat. For now it is too far out to really have a solid
handle on the environment, and without that it is pure speculation.
Winds become nely behind the front late Sat, and dry wx is then
ushered in for Sun and Mon. High temps both days slightly blw avg.
The modeling shows some sct-isold shwrs on the periphery of the
high, but with the cwa progged to remain right in the sfc ridge
axis, the fcst has been kept dry. Any change in this setup could
result in some sct aftn shwrs across the area. The next sys gets
here for the middle of the week. After a surge of warm air, a much
cooler airmass flows in behind a substantial cold front. 540
thicknesses are showing up on the maps with this one, although
whether they end up in nrn Quebec or nrn ME remains a question.
Chance pops have been included in the fcst. The NBM was generally
followed for temps thru the long term.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...
Weak high pressure over the region slowly slides east today.

VFR conditions through the TAF period.

W-SW winds 5-10 kt with coastal sea breezes developing by
afternoon at KJFK/KISP/KBDR/KGON. Trickiest forecast aspects
look to be timing of sea breeze arrival at KLGA late day, which
could occur a couple of hours later than forecast with a 180-190
degree direction (true) possible.

     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: Timing of southerly seabreeze may be +/- 1-2
hours from forecast.

The afternoon KJFK haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KLGA TAF Comments: Timing of seabreeze may be 1-2 hours later than
forecast with direction possibly 180-190 degrees true.

The afternoon KLGA haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KEWR TAF Comments: Gusts may diminish 1-2 hours earlier than
forecast.

The afternoon KEWR haze potential forecast is GREEN, which implies
slant range visibility P6SM outside of cloud.

KTEB TAF Comments: Gusts may diminish 1-2 hours earlier than
forecast.

KHPN TAF Comments: No unscheduled amendments.

KISP TAF Comments: Timing of seabreeze may be +/- 1-2 hours from
forecast.

.OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY...
.Fri...MVFR or lower conditions possible in showers/tstms mainly
late day/evening, but sct activity could occur near the NYC metros
as early as 17Z-19Z. S winds 10-15G20kt in the afternoon, except
gusty/erratic in/near tstms. Stronger sustained winds KJFK.
.Sat...MVFR or lower conds at times in any showers/tstms. W flow
becoming NE Sat eve.
.Sun...Chance of MVFR cigs in the morning.
.Mon...VFR.

&&

.MARINE...
High pressure remains south of the waters today. Westerly to sw
wind flow prevails, and seas remain 3 ft or less on the ocean
waters.

A backdoor front approaches tonight, but weakens or retreats to
the north Friday. Relatively light winds tonight will turn to
the south, and increase later in the day Friday ahead of a
frontal boundary. Seas build late in the day.

Winds and seas will likely hit sca lvls with strong sly flow on the
ocean Fri ngt, before subsiding just blw criteria on Sat. Elsewhere,
winds and seas look to remain blw criteria. Increasing ne flow on
Sun may result in sca cond, especially on the ocean. Winds and seas
all areas blw sca lvls Mon and Tue with high pres.

&&

.HYDROLOGY...
Dry conditions are anticipated through tonight.

Heavy tstms late Fri and Fri ngt could result in areas of minor
flooding. No hydrologic impacts are anticipated Sat-Wed.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Heat Advisory until 6 PM EDT Friday for NYZ071>075-176>179.
NJ...Heat Advisory until 6 PM EDT Friday for NJZ006-104-106>108.
MARINE...None.

&&

$$
SYNOPSIS...JMC/PW
NEAR TERM...JMC/Fig/PW
SHORT TERM...PW
LONG TERM...JMC
AVIATION...MD/24
MARINE...JMC/PW
HYDROLOGY...JMC/PW
EQUIPMENT...



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