Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 241750

Area Forecast Discussion
National Weather Service New York NY
150 PM EDT TUE MAY 24 2016

Low pressure south of Cape Cod tracks northeast today and tonight,
moving along the New England coast. High pressure builds in
briefly for late tonight and Wednesday. A cold front moves
through late Wednesday night into Thursday morning and lifts north
as a warm front later in the day Thursday. High pressure remains
situated over the western Atlantic through the first half of the
weekend. A backdoor cold front moves through on late Saturday
night into Sunday.


The forecast is pretty much on track here. There were some slight
adjustments to better match observed trends with regards to
temperatures, dewpoints, and pops for showers. Otherwise though, no
remarkable changes were made to the forecast database.

A weakening low south of Cape Cod tracks slowly northeast through
today. A weak surface trough extends back from the low into the
lower Hudson Valley. Meanwhile an upper closed, and nearly cutoff
low, east southeast of the Delmarva, as seen on the water vapor
loop, drifts north to northeast and begins to fill and get picked
up by the northern stream.

With areas of energy rotating around the low and the surface low,
showers will continue through this morning, eventually becoming
more scattered this afternoon. Instability is very weak this
morning and generally less than 50 J/KG but this will increase
this afternoon to a few hundred J/KG with increased daytime
heating at the surface. Forecast includes isolated thunderstorms
this afternoon.


Tonight the upper low continues to fill and becomes an open wave
after 06Z and the northern stream carries the low into Maine and
Nova Scotia, merging with low pressure over eastern Canada. The
surface low becomes nearly indistinguishable by late tonight, also
merging with a surface low over eastern Canada. By 00Z
precipitation is quickly ending as heights rise from as weak upper
ridging builds to the west. This ridge builds through Wednesday
with dry weather late this evening through Wednesday.

Warmer air continues to move into the region tonight through
Wednesday at the lower and mid levels. A dramatic warmup is
expected across the entire region as a westerly flow allows even
coastal areas to warm to well above seasonal normals.


A weak area of low pressure over the Canadian Maritimes will push a
cold front through the area Wednesday night. This front will then
head quickly back north as a warm front, moving through Thursday

Thereafter, there will be a prolonged period of southerly flow as
surface high pressure settles over the Western Atlantic. At the same
time, ridging aloft will mean rising heights and therefore, warming
temperatures, mainly for areas away from the coast. Closer to the
coast, flow off the cooler ocean waters will keep these areas a few
degrees cooler than inland. With a southerly flow, dewpoints will
also be on the rise. By the weekend, dewpoints could be in the lower
60s, making it slightly uncomfortable for some.

The 00Z ECMWF and the 00Z GFS are in better agreement on the passage
of a back door cold front late Saturday night into Sunday (quicker
than previously forecast). Thereafter, the 2 models differ. The GFS
continues to nose a strong high pressure from southeastern Canada
into the area, while the ECMWF keeps this high off the Atlantic
coast, and is weaker. Though the 00Z ECMWF does nose the high
pressure farther inland than the previous run. The GFS solution
would keep the area dry for the beginning of next week, while the
ECMWF would keep it unsettled. Due to the uncertainty, a blend of
models seems reasonable.

The cold frontal passages Wednesday night looks to come through dry
with limited moisture to work with. There may be some showers and
thunderstorms with the warm frontal passage on Thursday, mainly
inland as the lower temperatures over the coastal areas stabilizes
those areas. A thermal trough sets up over inland areas for Friday
and Saturday, which will mean diurnal showers and thunderstorms for
these areas. Showers and thunderstorms will also be possible with
the backdoor cold front passage late Sunday into Sunday night. This
will not be a continuous rainfall event from Friday through Sunday


Isolated to scattered SHRA/TSRA will pass through the terminals
through this evening. Will carry VCSH/VCTS in the 18Z TAFs through
this evening, but confidence on timing and coverage is low.

Generally a VFR forecast. Conds may briefly lower to MVFR in
SHRA/TSRA. In addition, MVFR VSBY possible in areas of BR late
tonight, mainly away from KNYC terminals.

Winds generally ranging from N to NW at 5-10 KT. Winds become
LGT/VRB this evening and tonight.

     ...NY Metro Enhanced Aviation Weather Support...

Detailed information, including hourly TAF wind component
forecasts, can be found at:

KJFK TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds. Low confidence on sea breeze

KLGA TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds. Low confidence on sea breeze

KEWR TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds.

KTEB TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds.

KHPN TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds. Low confidence on sea breeze

KISP TAF Comments: Occasional SHRA/TSRA possible through this
evening with brief MVFR conds. Low confidence on sea breeze

.OUTLOOK FOR 18Z Wednesday through Sunday...
.Wednesday through Thursday...VFR.
.Thursday night through Friday morning...Occasional MVFR in
showers/thunderstorms possible.
.Friday-Saturday...MVFR possible in afternoon/evening tstms.


A weak pressure gradient force will be across the waters through
Wednesday as a weakening low south of Cape Cod tracks to the
northeast through tonight and high pressure builds in late tonight
and Wednesday.

The only hazard across the forecast waters will be isolated
thunderstorms this afternoon into early this evening. Otherwise
no hazardous conditions are expected.

Winds and waves should remain below SCA criteria for the long term
with light a pressure gradient.


Rainfall amounts of less than 1/4 inch are expected for the rest
of today into this evening. Locally higher amounts will be
possible in isolated thunderstorms.

No concerns for hydrology Wednesday through Monday.




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