Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
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FXUS61 KOKX 290135
Area Forecast Discussion
National Weather Service New York NY
935 PM EDT SAT MAY 28 2016
Bermuda high pressure persists through Sunday. The high weakens
and moves farther out into the Atlantic Sunday Night into Monday.
Meanwhile, a parent low moves from Ontario into Quebec with an
associated cold front approaching. The region stays within the
warm sector Sunday Night into Monday. A cold front is forecast to
cross the area Monday night into Tuesday with Canadian high
pressure building in behind it from the north.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --Forecast on track with only minor adjustments needed this eve.
Convection has diminished with dry weather expected through the
rest of the night.
With Bermuda high pressure still in place, there will be south to
southwest flow along the coast. This will keep a warm and humid
airmass in place. Interior locations will have lighter winds.
Lows will be mild and well into the 60s. A combination of
radiational cooling and onshore flow will lead to some patchy fog
formation for those locations cooling more efficiently where winds
decouple under mainly clear skies.
Used warmer MAV guidance for lows tonight.
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.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
For Sunday Morning, some patchy fog to start out will then dissipate
with diurnal heating. Once again with the Bermuda high in place, the
winds will be out of the south to southwest. Another warm and
humid day is expected. 850mb temperatures are forecast to be
nearly the same to slightly less than Saturday`s values.
In terms of convection, the upper level ridge axis will be sliding
east of the region, allowing for a lowering of heights Sunday
Afternoon into Sunday Evening. This will aid dynamic lift judging by
today and how convection is developing north and west of NYC. For
Sunday Afternoon into Sunday Evening, heights are even lower, about
30-40 meters lower at 500mb. The scattered coverage will extend
farther south and east across NYC into Western Long Island. This
further increases Sunday Night with a continuance of lowering
heights aloft. There will therefore be less subsidence and more lift
as a shortwave approaches riding along the NW edge of the upper
level ridge, the axis of which will be over the open Atlantic.
Instability for thunderstorms will be mostly near where there is
higher CAPE, mainly north and west of NYC so greater chances of
thunderstorms will be there.
Used warmer MET guidance for interior and a blend of MAV/MET for
the coastal areas for highs on Sunday.
The southerly flow continues at the surface, moistening the low
levels further. There will be a potential for heavy rain especially
late Sunday Night through Monday as precipitable waters increase to
near 2 inches as there will be some tropical moisture entrainment
into the region as well. The bulk of the rain as conveyed by
numerical weather prediction QPF fields looks to be 06Z to 18Z
Monday. Rain looks to linger Monday Afternoon but the high
precipitable water axis will be moving across Eastern Long Island
and Southeast Connecticut, keeping more of the relatively heavier
rain potential in those locations with lighter rain to the west.
Outside of any heavier rain, Sunday Night into Monday will have
some patchy fog lingering as well.
Used the warmer MAV guidance for lows on Sunday Night.
Looking at the vertical wind profiles through the atmosphere,
there is a deep layer of south to southwest flow. The jet comes
into play early Monday Morning through much of Monday Afternoon
with a right rear quad between of 50 to 70 kt across the region,
lighter part of the range towards the coast and higher part of the
range inland. This will allow for widespread and potentially heavy
rainfall. The uniformity of flow from low to upper levels will
allow for training of cells as well. Instability will be less and
elevated so for thunderstorms, will just have chance of
These aforementioned factors signal a potential predecessor rain
event but there is uncertainty on where the heavy band of rain sets
up. The confidence at this time of where exactly the heavy rain
occurs is low so chance for flooding is at this time around 30
Used the GMOS for Monday high temperatures.
There is a moderate risk of rip current development at Atlantic
ocean beaches on Sunday.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Models have come into somewhat better agreement with the overall
H5 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 into the
northeast Monday night and appears to keep the remnant low over
the Carolinas from being picked up by the northern branch of the
jet stream. The 12z EC is slower than the GFS moving the cold
front and pcpn out of the area Mon night and even lingers it in
srn zones into Tue morning. Have kept chc pops in during the
eve...but pcpn may linger longer than forecast...especially e of
nyc...if the front is slower to move across or even gets hung up
over the area. In fact...the EC slowly tracks the low up the
eastern seaboard while the GFS keeps it nearly stationary over
the Carolinas through the middle of the week until its finally
picked up by the next trough. While the current forecast is dry
tue through thu...this may change depending on the eventual upper
pattern which does have differences by this time and is leading to
A pre-frontal trough on fri ahead of the approaching upper trough
and associated sfc cold front should trigger shower and tstm
activity mainly from NYC and areas n and w on fri and across the
area into sat as the front moves through.
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
High pressure will remain nearly stationary across the western
Atlantic through Sunday with a thermal trough across the interior
in the afternoon.
Convection has dissipated across the area with no additional
activity forecast overnight. There is a low chance of
afternoon/evening convection Sunday, primarily north and west of
the NYC terminals.
Winds may be variable in and around the NYC terminals early due
to the dissipated convection, otherwise S/SW flow this evening
diminishes to less than 10 kt. KISP and KJFK may experience an
occasional gusts up to 20 kt early as the coastal jet weakens.
Persistence type of forecast Sunday with seabreezes once again
developing with local enhancements in the afternoon.
MVFR fog is possible late tonight at KSWF, with a low chance
across the remainder of the non-NYC terminals.
.OUTLOOK FOR 00Z Monday through Thursday...
.Sunday night-Monday...MVFR or lower likely after midnight.
Showers/thunderstorms could produce locally heavy rainfall.
.Monday night-Tuesday night...Becoming VFR Monday Night.
.Wednesday and Thursday...VFR.
Through Monday, the pressure gradient will be weak and diffuse. This
will allow for winds and seas to stay below sca thresholds.
Have capped seas at 4 ft Mon night into Tue as both wavewatch and
swan appeared high with no real swell component present and a
relatively light sly flow. otherwise...sub-advsy conds are
expected through the remainder of the forecast period.
No significant widespread precipitation is expected through Sunday.
For Sunday Night through Monday Evening...widespread rainfall is
forecast. While rainfall totals are forecast to range from around
1 to 1.5 inches, some locally higher amounts are quite possible
and it will be in these locations where the heavy rain bands set
up, that there will be a chance of flooding. The type of flooding
possible would be that or urban and small stream mainly.