Area Forecast Discussion
Issued by NWS Upton, NY

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899
FXUS61 KOKX 221458
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1058 AM EDT Mon May 22 2017

.SYNOPSIS...
High pressure moves east of the New England coast today ahead
of a cold front approaching from the west. The front moves
through tonight followed by brief high pressure for tomorrow
ahead of an area of low pressure that will pass to the south
Tuesday night. Another low and frontal system approaches
Wednesday and Thursday, and passes to the east late in the week
and into the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Updated probabilities through tonight as indications are the
shortwave will slide a little farther to the south late this
morning and into this evening. Also with the low level jet just
south and across the east end of Long Island removed the mention
of the widespread moderate rainfall. However a brief period of
moderate rainfall is still possible across Long Island.

Sounding are saturated through this afternoon, with little to
no CAPE both surface based and elevated, so have removed the
mention of thunder.

Outside of the afternoon, model sounding profiles generally
lean more towards a stratus/drizzle profile which should help to
reduce overall rainfall amounts.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
By evening, rainfall will gradually decrease from west to east.
There may be a brief period of fog as moisture remains beneath
the inversion until the cold front moves through leading to
drier conditions overnight. Low temperatures will be closer to
climatological normals due to cloud cover and initially strong
winds that will gradually decrease through the morning.

Although a short wave is progged to move through the region
Tuesday afternoon, forecast upper divergence appears supportive
of a more southerly track of a developing surface low, which
should limit overall rainfall totals across the area. Much of
the day may remain dry through the day. Temperatures will be
warmer due to offshore flow, with highs closer to or slightly
below climatological normals.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Still note some differences in upper level pattern, with regard to
handling large midwest trough that eventually ejects to the east,
kicked by upstream low. This trough/closed low passes overhead by
Friday, then moves east next weekend. Weak ridge builds behind.

For the Tuesday night-Wednesday time frame, shortwave embedded in
broad southwest flow passes Tuesday night into early Wednesday.
A wave of low pressure at the surface passes to the south, and the
local area could get clipped with rain, with best chance along the
coast, and less of a chance as you head north and west. NWP suite is
now tracking this low similarly. Dry air in the lower levels, along
with best lift to the south may preclude much in the way of rain for
our area.

Once that wave passes, dry weather should return briefly, although
cannot rule out an isolated shower Wednesday. Then, the next chance
arrives Thursday as the upper trough tracks east, approaching the
area. Surface low and front approach, and showers will be likely
Thursday into Thursday night based on latest model timing. Warm
front likely remains just south of the area Thursday, with sfc low
and occluded front passing Thursday night. Weak instability noted,
so will maintain thunder mention.

Depending on how this trough evolves, there could be lingering
instability showers/thunderstorms Friday as the system moves across
the northeast.

Much uncertainty next weekend, but dry weather should prevail
Saturday for the most part, with Sunday less clear due to model
differences in timing of next upstream shortwave/sfc warm front.
ECMWF still the more progressive model with this feature Sunday.

Daytime highs will be near or just below normal mid week, then warm
a few degrees closer to normal levels late in the week into next
weekend.

At night, lows will run around 5 degrees above normal late in the
week and through the weekend.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
A weak frontal system will move across the area the next 24
hours.

Ceilings will gradually lower to IFR into early this afternoon
and then remain through most of tonight. There is uncertainty
with the timing of lowering conditions as well with the rain.

SE winds 5-10 kt gradually increase, generally 8 to 13 kt.
Occasional gusts up 15-18 kt possible today.

     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: Onset of IFR conditions could vary by several
hours. Winds may back more easterly.

KLGA TAF Comments: Onset of IFR conditions could vary by several
hours. Winds may remains more east.

KEWR TAF Comments: Onset of IFR conditions could vary by several
hours. Winds may back to the E/NE in the late afternoon.

The afternoon KEWR haze potential forecast is YELLOW, which
implies slant range visibility 4-6SM outside of cloud.

KTEB TAF Comments: Onset of IFR conditions could vary by several
hours. Winds may back to the E/NE in the late afternoon.

KHPN TAF Comments: Onset of IFR conditions could vary by several
hours.

KISP TAF Comments: Onset of IFR conditions could vary by several
hours. Winds may remain more easterly.

.OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY...
.TUESDAY...Becoming VFR in the morning. Possible late day rain
near the coast.
.WEDNESDAY...VFR.
.THURSDAY...Possible IFR conditions in rain. Slight chance of
thunderstorms Thursday evening.
.FRIDAY...MVFR or lower possible in showers.

&&

.MARINE...
East to southeast winds were a few knots below current forecast
and as a result seas were also about a foot below forecast
values. Made adjustments to both the winds and seas into this
afternoon.

A warm front approaches today, followed by a cold or occluded
front tonight. SE winds should remain below 25 kt or SCA
thresholds. These winds shift to the S, then shift all the way
around to the NW or N late tonight.

A wave of low pressure passes south of the waters Tuesday night into
Wednesday. Then a warm front approaches Wednesday night and
Thursday. Low pressure tracks across the waters Thursday night and
moves east by Friday.

Shifting winds are anticipated through the period in this somewhat
active pattern, but speeds should remain below SCA thresholds.

Seas on the other hand may remain elevated across the ocean waters
on the backside of the first low Wednesday, and again behind the
second stronger low Friday. Otherwise, seas remain rather tranquil
through the mid to late week period.

&&

.HYDROLOGY...
Rainfall accumulations of a 1/4 to 3/4 of an inch, with locally
up to an inch possible, especially across the southern forecast
area, today through Tuesday morning.

Unsettled weather is expected mid to late week, but no
hydrologic impacts are anticipated at this time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...MD
NEAR TERM...MET
SHORT TERM...MD
LONG TERM...PW
AVIATION...IRD
MARINE...MD/MET/PW
HYDROLOGY...MD/PW



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