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Area forecast discussion 
National Weather Service New York New York
1159 am EDT Wednesday Jul 29 2015

Synopsis...
high pressure will build off the middle Atlantic coast today. A cold
front will then approach from the west tonight into Thursday
morning...and move across Thursday afternoon and night. A series
of weakening cold fronts will approach...the first during Saturday
night...and another Sunday night into early next week...while high
pressure remains over the western Atlantic.

&&

Near term /through tonight/...
a deep layered northern stream ridge continues to build over the
County Warning Area today...with the ridge axis passing over the area tonight.
Subsidence under the ridge will keep things dry through
tonight. Cloud cover will also be at a minimum...other than maybe
some afternoon cumulus...until some high clouds begin to build in
from SW to NE late tonight as the ridge axis moves to the east.

Main story today will be the heat...with highs 90 to 95...except
85 to 90 middle on the immediate South Shore of eastern Long Island
and southeast CT. These temperatures combined with dewpoints mostly in
the middle and upper 60s will yield maximum heat index values in the middle
and upper 90s. Heat advisory continues for NYC.

Lows tonight are an 06z mav/00z met blend.

There is a moderate rip current risk at the ocean beaches.

&&

Short term /Thursday through Thursday night/...
the deep layered northern stream ridge exits to the east Thursday
morning...with a northern stream trough moving in behind it
through Thursday night. Precipitation will generally run ahead of
the trough...and not to far ahead of its associated surface cold
front. Confidence in the occurrence of precipitation has lead to
an increase of probability of precipitation to likely Thursday afternoon and evening.
Along with this...have also put a mention of locally heavy
rainfall in the forecast. Refer to the hydrology section for
details on amounts and any potential impacts.

However...with model guidance still showing some warming in the
layer from around 650-550 mb...have kept the probability of
thunder to chance. Models are fairly consistent in the timing of
the end of precipitation...and so expect it to come to an end from
northwest to southeast Thursday night as the surface cold front exits to the
east.

Generally have 1500-2000 j/kg of surface based cape forecast over
all of the County Warning Area but the Twin Forks and the immediate coast of southeast
CT. With a bulk shear of around 30 knots...favor a combination of
pulse storms and some multi-cellular clusters and/or bowing
segments. With the region forecast to be in the right rear
quadrant of an around 80 knots 250 mb jet...and the passing of a
25-30 knots 950-850 jet near/over the area Thursday
afternoon/evening...there is sufficient forcing to go along with
the cape and shear for strong to possibly severe storms.
Accordingly Storm Prediction Center has expanded the marginal risk of severe
thunderstorms to encompass all but basically southern Suffolk
County. Will make a minor adjustment to this for the severe weather potential statement...and
highlight the severe threat for all but eastern Suffolk
County...noting the lower convective available potential energy there.

Highs on Thursday should be a few degree cooler than those of
today...but with higher dewpoints maximum heat index values should be
only slightly lower than those of today...still reaching the middle
and upper 90s except in the higher elevations and eastern coastal
sections...so the heat advisory will continue for NYC.

Lows Thursday night should still be about 5 degrees above average.

&&

Long term /Friday through Tuesday/...
overall Friday into next week...no significant large scale changes
within the region in the middle to upper levels. The main upper level
jet stays mostly northeast of the region with the 250 mb height
gradient gradually decreasing going into next week. The 500 mb
heights are forecast to generally stay between 576-582 dm much of
the period. The lowest heights will be marked by the the passage
of shortwaves within a longwave trough over the northeast.
These are shown to occur Saturday night into early Sunday as well
as Monday night into Tuesday. The local region will be at the base
of this longwave trough. Much of the positive vorticity advection
will be located north of the region...leaving a void in synoptic
forcing over the local area.

The middle levels will likewise exhibit similar trends at the surface
with overall a weak pressure gradient remaining. The cold fronts
approach Saturday night into early Sunday and early next week with
weak high pressure for other time periods within the long term. The
fronts dissipate without much change of air mass for the region.

Therefore...the probability of precipitation for showers and thunderstorms will in the
slight chance range due to timing at night with less instability and
the aforementioned lack of synoptic forcing for this Saturday night.
The probability of precipitation are also slight chance for early next week due to larger
uncertainty but with some more instability to work with potentially
for any convection during the day.

The air mass will continue to be very warm and humid. Much of the
area has forecast highs of middle 80s to near 90 with forecast lows
middle 60s to lower 70s. The dewpoints are forecast to stay well
within the 60s much of the time period.

&&

Aviation /12z Wednesday through Sunday/...
a weak low pressure trough will remain over the area this
afternoon...while high pressure remains to the west.

VFR. Most terminals winds come from the S/SW this afternoon with
speeds increasing to at least 10 knots for coastal airports. JFK
likely to get up to 15 knots or even stronger with coastal jet for
the late afternoon.

MVFR visibility in fog/haze toward 12z Thursday. Possible rain showers/thunderstorms and rain after
12z Thursday at 30h taf sites.

New York metropolitan enhanced aviation weather support...

Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)

Kjfk fcster comments: wind direction may vary 160-180 in the
afternoon.

Klga fcster comments: wind direction may vary 160-180 in the
afternoon.

Kewr fcster comments: wind direction may vary 150-210 in the
afternoon.

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

Kteb fcster comments: wind direction may vary 160-210 in the
afternoon.

Khpn fcster comments: wind direction may vary 160-200 in the
afternoon.

Kisp fcster comments: no unscheduled amendments expected.

Outlook for 12z Thursday through Sunday...
Thursday...early morning haze with MVFR conditions...then scattered
afternoon/evening thunderstorms with MVFR or lower conditions.
Fri-Sunday...VFR.

Outlook for 12z Thursday through Sunday...
Thursday...early morning haze with MVFR conditions...then scattered
afternoon/evening thunderstorms with MVFR or lower conditions.
Fri-Sunday...VFR.

&&

Marine...
a weak to moderate strength pressure gradient will generally keep
winds at 15 knots or less through Thursday night. However...could
see a combination of the tightening of the pressure gradient
ahead of a cold front and the sea breeze bring winds to 20 knots in
the New York bight region Thursday afternoon/evening. For now it appears
though that any gusts to 25 knots in this region will be occasional
at most. Given this...and current expectation of no significant
swell through Thursday night...expect seas to remain below 5 feet
through Thursday night also.

Sub Small Craft Advisory conditions are forecast on Friday and Friday night with weak
high pressure moving across. The below Small Craft Advisory conditions are forecast
to continue into much of Saturday until some higher seas from
continued southerly fetch will move in late Saturday afternoon
through Sunday. Ocean seas are forecast to reach 5 to 7 feet with this
fetch...so Small Craft Advisory potential will be there.

&&

Hydrology...
dry through tonight.

Around 1/4-1/2 inch of basin average rainfall is possible Thursday and
Thursday night. However...with precipitable waters forecast to
over 2 inches Thursday afternoon and evening...locally heavy
rainfall is possible with any stronger convection. If this
occurs...then minor urban/poor drainage flooding would be
possible.

No significant widespread rain expected Friday through Tuesday.

&&

Climate...
record highs for Wednesday July 29 2015...

Location..........record high/year.........Forecast high
Newark....................100/1949.................96
Bridgeport.................96/2002.................93
Central Park...............99/1949.................96
LaGuardia..................97/1949.................96
Kennedy....................99/2002.................95
Islip......................96/2002.................92

&&

Okx watches/warnings/advisories...
CT...none.
New York...heat advisory until 8 PM EDT Thursday for nyz072>075-176-178.
New Jersey...none.
Marine...none.

&&

$$
Synopsis...maloit/jm
near term...maloit/jm
short term...maloit
long term...jm
aviation...dw
marine...maloit/jm
hydrology...maloit/jm
climate...

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