Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 240817

Area Forecast Discussion
National Weather Service New York NY
417 AM 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.


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 today.
With weak surface and mixed layer instability along with a cold
pool associated with the upper low, isolated thunderstorms will
be possible. Have kept a mention through the day, however, believe
the best chances will be this morning through 18Z. Afterward low
level warm advection sets up and caps the area lessening threat of
thunder. Some weak elevated cape is available in the afternoon.


Tonight the upper low continues to fill and becomes an open wave
after 06Z and the northern stream carrys 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


Low pressure moves north toward Cape Cod this afternoon.

Primarily MVFR through this morning. Some IFR possible as well,
primarily east of the city terminals. Improvement to VFR expected
this afternoon. Rain will be steadiest through mid-morning, then
more scattered thereafter. Isolated thunder possible at any time
today, but timing and location not certain enough for inclusion
in TAFs.

Low confidence with wind direction, however speeds should at least
remain below 10 kt.

.OUTLOOK FOR 06Z Wednesday through Saturday...
.Tuesday night-Thursday...VFR.
.Thursday night...Low chance of MVFR in showers.
.Friday-Saturday...MVFR possible in afternoon/evening tstms.


A weak pressure gradient force will be across the waters today
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 today 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 1/3 to 3/4 of an inch are possible today into
this evening with the highest amounts across western Long Island,
southwestern Connecticut, and Northeastern New Jersey. Locally
higher amounts will be possible in isolated thunderstorms.

No concerns for hydrology Wednesday through Monday.




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