Area Forecast Discussion
Issued by NWS Upton, NY

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486
FXUS61 KOKX 291518
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1118 AM EDT SUN MAY 29 2016

.SYNOPSIS...
Westward extension of a Bermuda high pressure persists through
today. The high weakens and moves further into the Atlantic
tonight into Monday. A cold front will move across the area Monday
night into Tuesday. High pressure returns through the end of the
week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Based on latest satellite imagery and latest guidance, have opted
for more sunshine today. This only results in some minor changes
to other forecast elements. Have also backed off on convective
chances this afternoon with ridging aloft and lack of a surface
trigger. Convective temps will be close inland. In addition,
temps are forecast to be a bit cooler and there is some drier air
aloft over the Mid Atlantic states working northward this
afternoon that could be an additional limiting factor. Any
convection looks to be isolated and of the pulse variety with
moderate to high capes inland but weak shear.

With westward extension of Bermuda high pressure over the region
and deep upper ridge over the area, feel conditions today will be
similar to those observed on Saturday. Have went above guidance
with high temperatures away from the immediate coast. Flow
initially starts out southwesterly, but will become southerly in
the afternoon. This should cap temperatures at the immediate coast
in the upper 70s to near 80 degrees, and conditions could even be
a bit cooler over the Forks of Long Island and SE CT. Highs from
the city north and west will be in the upper 80s and lower 90s.
While the flow becomes southerly in the afternoon, locations north
and west of the city will warm quickly and should still obtain
forecast highs.

There is a moderate risk of rip current development at Atlantic
facing beaches today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Main focus this period is on potential heavy rain event late
tonight through Monday.

Heights continue to fall aloft this evening and southwest flow will
be on the increase. Tropical moisture will quickly advect northward
as the the flow taps into moisture from Bonnie across the Carolinas.
Precipitable water values are progged to be near 2 late tonight into
Monday. These values are close to the highest observed for May 30
per SPC Sounding Climatology across the area. This coupled with
shortwave energy approaching from the west and the region being
located in the right entrance region of an upper jet to the north
sets the stage for heavy rainfall.

Models continue to show spread on rainfall amounts late tonight
through Monday. SREF plumes show several members with rainfall
under a half inch and some members approaching 1.5 inches with the
mean right around 1 inch. Meanwhile, the GEFS plumes show a
clustering between 1 to 1.5 inches of rainfall especially east of
the Hudson River. There is a fairly high confidence that bands of
heavy rain will develop late tonight across western zones and then
move to the east through the day on Monday. There could be
training of cells as larger bands of rain move to the east, so
locally heavy rainfall is possible. There continues to be
potential for minor urban and small stream flooding and it would
not be out of the question for localized flash flooding. However,
confidence is low on where this may occur so have will not issue a
watch at this time. This is in collaboration with all neighboring
offices and will continue to mention potential in the HWO.

Instability is lacking during this event so will only show a
mention for isolated thunder. Rain tapers off from west to east
across the area in the afternoon and evening. Cannot rule out a
few showers behind the main plume of moisture as a cold front
moves across the area so will show slight chance pops overnight.

Temperatures on Monday will much cooler than recent days as abundant
clouds and precipitation will hold readings in the 70s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Models continue to slowly come into better agreement with the
overall 500 hPa pattern across North America, although timing and
amplitude differences still become apparent by the middle of the
week which is impacting the progression of a cold front late in
the week.

Approaching shortwave trough flattens as it moves across Tuesday
morning. Interestingly, the 00z ECMWF keeps a stronger trough and
helps pull more tropical moisture towards southern portions of the
region Tuesday morning. This solution appears to be an outlier at
time, but will hold onto slight chance pops near Long Island as do
not want to completely discount the idea that a few showers
develop with the passage of the flattening trough. Cold front
moves offshore on Tuesday and ridging begins to build aloft later
Tuesday into Tuesday night. This ridge dominates the weather
through Thursday with surface high pressure moving across New
England Wednesday into Thursday. The 00z ECMWF tries to bring
some remnants of Bonnie towards the area on Thursday, but
currently feel this is overdone with ridging aloft and subsidence
at the surface from high pressure just to our northeast.

A cold front approaches on Friday and will slowly move east into
Saturday. Not much instability noted in model soundings so will
just advertise a chance of showers with the front.

Above normal temperatures return on Tuesday and Wednesday before
an onshore flow will bring temperatures down to near normal levels
for the end of the week.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
The region will remain under the influence of a westward extension
of the Bermuda High today. A trough of low pressure builds into
the Lower Hudson Valley Tonight.

Most likely VFR through this afternoon. There is quite a bit of
uncertainty on whether low clouds (IFR or lower) move in late this
afternoon/this evening at Long Island/Coastal CT terminals and
KJFK. This could happen as early as 23-00z KGON and 1-2z
KJFK/KISP/KBDR. For now time with onset of moderate showers at
each terminal...except start at 4z at KGON.

Showers should move into area terminals from SW to NE tonight
with conditions deteriorating down to MVFR/IFR as the showers move
in.

SW-S flow under 10 kt gives way to seabreezes (around 10-15kt) at
all but KSWF this afternoon. Could see isolated gusts to around
20 kt at coastal terminals...maybe even 25 kt at KJFK. Winds
become light and variable throughout this evening.

.OUTLOOK FOR 12Z Monday through Thursday...
.Monday...MVFR or lower likely. Showers/thunderstorms could
produce locally heavy rainfall.
.Monday night-Tuesday night...Becoming VFR Monday Night.
.Wednesday-Wednesday night...VFR.
.Thursday...Low chance of MVFR or lower. E-SE winds g15-20kt
possible.

&&

.MARINE...
Forecast on track over the forecast waters.

A weak to moderate pressure gradient over the region through
Thursday will keep sustained winds to 15 kt or less over the waters
around Long Island.

There is quite a bit of uncertainty on how much residual swell from
Tropical Cyclone Bonnie will impact the coastal ocean waters early
next week. As a result, seas to around 5 ft cannot be ruled out
mainly in the Monday-Tuesday time frame on the coastal ocean waters.
However, the confidence in this occurring is too low to warrant
mentioning in the forecast at this time.  Outside of this
potential, seas should remain below Small Craft levels through
Thursday as well.

&&

.HYDROLOGY...
No widespread precipitation is expected today.

For tonight through Monday Evening...a widespread 1 to 1.5 inches
of rain is forecast. Locally higher amounts are also possible.
This rain could lead to minor urban and small stream flooding and
there is chance for localized flash flooding as well.

&&

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

&&

$$
SYNOPSIS...DS
NEAR TERM...DS/DW
SHORT TERM...DS
LONG TERM...DS
AVIATION...Maloit/JM
MARINE...Maloit
HYDROLOGY...DS



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