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Area forecast discussion 
National Weather Service New York New York
643 am EDT Wednesday may 6 2015

Synopsis...
a slow moving cold front south of Long Island will continue to sag
south of the region today...allowing high pressure to build in for
Thursday. A frontal boundary will back into the region from the
northeast on Friday...then lift out on Saturday. High pressure
over the Atlantic then remains in control through the rest of the
weekend. Low pressure off the southeast coast will track slowly
along the middle Atlantic coast into early next week...then track out
to sea as a cold front approaches from the west.

&&

Near term /until 6 PM this evening/...
forecast is generally on track. Radar imagery looks worse than
reality due to a very dry subcloud layer (20 degree dewpoint
depressions at the sfc). Left probability of precipitation at high chance as a result with
scattered showers. Hourly T/dew point needed adjusting as temperatures are higher than
forecast and dewpoints are lower. No other adjustments needed.

The 00z models are basically dry for today. However...satellite and
radar indicate bands of showers rotating into the region from the
west...the remnants of Midwest convection. The 00z okx sounding had a
precipitable water of 1... the additional moisture advection should allow for
at least some pockets of measurable precipitation across the southwestern 2/3 of
the County Warning Area. The limiting factor will be the developing NE flow behind
the cold front just S of Li...where the 00z chh sounding just upstream
had a precipitable water of 0.83. Gyx was even lower at 0.23. As a result...probability of precipitation
were capped at scattered coverage for today...with decreasing chances from
NE to SW in the afternoon...ending by this evening. The cloud shield will
likewise erode...but with infrared showing the middle cloud belt still
stretching from Lake Ontario westward to Lake Michigan...have forecast a
mainly overcast day. Temperatures a blend of the guidance...with the warmest
readings across the interior valleys.

&&

Short term /6 PM this evening through 6 PM Thursday/...
upper ridge builds in with decreasing moisture and increasing
subsidence. There is a hint of convective initiation in all the
00z models Thursday afternoon...but it appears to be terrain induced...and
with the weak steering flow do not expect any of the precipitation to reach
the County Warning Area at this time. The end result is a dry forecast. Temperatures a blend of
guidance tonight...and a blend of the mosg25 and namdng5 for
Thursday...where the weak gradient flow should allow for extensive and
early sea breeze development yielding much cooler temperatures along the
coasts.

&&

Long term /Thursday night through Tuesday/...
model guidance looks to start off in good agreement with an
amplified ridge over the northestern Continental U.S. And eastern Canada. They start to
diverge fairly quickly as the GFS moves the ridge offshore and
breaks it down quicker than the ec. Since this is a known bias of
the GFS...have sided with the ec solution which has support from the
CMC. As a result...have kept the weekend dry...which may also
continue into Monday...although there is uncertainty with a low
pressure system tracking along the eastern Seaboard early next week
as well as how far S a frontal boundary drops down from the north. Have
decided not to make huge changes Monday through Wednesday...but we may not
see a widespread rainfall until an upper trough and surface cold frontal
passage Tuesday/Tuesday night.

There is also the signal for several days of fog and stratus at
night and into the morning beginning Friday night (could have patchy
fog in some isolated spots Thursday night) with several days of southerly flow in
place. Have added this to the forecast Sat and sun for now.

Temperatures are expected to be above normal levels through the period.

&&

Aviation /12z Wednesday through Sunday/...
a cold front south of Long Island will move further south today as
high pressure builds over the terminals.

VFR through the taf period.

Shower activity moving towards the terminals from the west will
affect kswf early this morning. There still is some uncertainty
if these showers will make it further east. For now...have
included vcsh after 12z for all but kgon. If showers occur...VFR
conds are still expected.

Winds this morning will be out of the NE with speeds around 10
knots. Winds veer to the east and then southeast this afternoon into the early
evening hours. Winds diminish tonight and become light and
variable.

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: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

Klga fcster comments: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

Kewr fcster comments: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

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

Kteb fcster comments: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

Khpn fcster comments: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

Kisp fcster comments: timing of wind shift this afternoon to the
southeast may be off by +/- and hour or two.

Outlook for 06z Thursday through Sunday...
Wednesday night-Friday...VFR.
Saturday-Sunday...potential for IFR or lower in stratus and/or fog
at night and the morning. Otherwise VFR.

&&

Marine...
winds and seas will remain blw Small Craft Advisory levels through Thursday as hi pressure builds
in from the northwest.

For Thursday night through Monday...winds are expected to remain below advsy
criteria through the period...although could gust around 20 knots Sun
afternoon/evening with a tightening pressure gradient. Seas could reach
marginal Small Craft Advisory levels on the ocean waters Sun night into Monday as
swells from low pressure off the middle Atlantic coast develop.
Otherwise...sub-advsy conds are expected.

&&

Hydrology...
a few hundredths of an inch of precipitation are possible today.
Thereafter...no precipitation is expected through the weekend.

&&

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

&&

$$
Synopsis...jmc/24
near term...jmc
short term...jmc
long term...24
aviation...ds
marine...jmc/24
hydrology...jmc/24

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