Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 210752

Area Forecast Discussion
National Weather Service New York NY
352 AM EDT Sat Apr 21 2018

High pressure builds in from the west through the weekend, and
remains over the region into Monday. A coastal low will affect
the region the middle of next week, possibly lingering into late


Deep closed low continues to lift north of New Foundland, with mean
troughing continuing over the NE US in its wake. At the surface,
high pressure builds into the region from the west. Although a weak
backside shortwave will have a surface trough moving through the
region in the afternoon/evening.

Continued W/NW flow today, but weaker than Friday. A gradual
moderation in airmass and deep mixing should allow temps to rise
into the mid to upper 50s. Late day seabreeze possible along
the immediate south coasts. Mostly sunny skies expected, just
few-sct afternoon CU across NE portions of the region with
late day shortwave/trough passage. Otherwise just a few wisps
of cirrus.


Tranquil period with mean troughing in control of the NE US
through the weekend, then giving way to shortwave ridging Sunday
night into Monday. At the surface, high pressure will continue
to build in from the west Sunday and overhead on Monday.
Although, a weak front will move through the region late Sunday
in response to one final kicker shortwave moving through the

A couple of clear and chilly nights tonight and Sunday Night.
Areas of frost expected across outlying areas with good
radiational cooling into the upper 20s to lower 30s. Elsewhere
lows generally in upper 30s to lower 40s, and slightly milder
NYC/Nj metro.

Otherwise, mostly sunny, tranquil and seasonable Spring
conditions Sunday and Monday. Highs generally in the upper 50s
to lower 60s on Sunday, with cooler temps along the south coasts
with afternoon sea breeze development. A bit warmer conditions
likely Monday (lower to mid 60s) , especially NYC/NJ metro and
interior, with continued moderation of airmass and developing
return flow. Along the coast, temps will likely hold in the
upper 50s to lower 60s with return flow and sea breezes
developing in the afternoon.


Upper air pattern will very much resemble early springtime as an
upper low over the Mississippi Valley this weekend slowly works east
on the heels of the departing trough over the Northeast. Models in
good agreement with this energy and associated low pressure system
lifting northward towards the region Tuesday into Wednesday in
response to northern stream shortwave energy moving into the upper
Midwest and Great Lakes. Overrunning rains are likely to develop
across the area Tuesday night and continue through Wednesday,
possibly Wed night.

Thereafter, models diverge in the amplification of this shortwave
energy over the the Upper Midwest and Great Lakes region during the
midweek period. This is further complicated by differences in
the amplification the next northern stream shortwave diving
into the Great Lakes and Mississippi River Valley for late week.
The evolution of these two troughs will determine the details
for the next low pressure system/s affecting the region Thu
thru Sat. A chance of showers remain in the forecast during this
time to denote the potential.

So uncertainty in the guidance for the end of the week continues,
however, the global models continue to point to some degree of
troughing reestablishing itself across the Northeast for next

As for temperatures, much of the period will feature seasonable
temperatures with the exception of Wednesday, where onshore flow
will keep highs several degrees below normal.


High pressure will build in through the TAF period going into early
Sunday. VFR conditions are expected. Winds will be near 10 kt or
less through much of the TAF period mainly from W to NW direction.

The winds will initially be NW going into early today and then back
to a more westerly direction during the afternoon with some SW flow
as a sea breeze for some terminals. Also for this afternoon into
early evening, there will be some wind gusts to 15-20 kt. The timing
and duration of any sea breezes is uncertain with wind direction
possibly varying about 20-40 degrees comparing observed to forecast
for this afternoon. The timing of the SW flow could also be 2-3
hours off from forecast.

.Late tonight through Tuesday...VFR.
.Tuesday night through Wednesday...MVFR or lower conditions
increasingly likely with rain.


Tranquil conditions expected this weekend through next Tuesday with
high pressure in control and a weak pressure gradient.

Low pressure moving up the eastern seaboard Tuesday into
Wednesday will result in increasing winds and building seas with
SCA conditions likely to return by Wednesday morning.


Dry conditions are expected through Tuesday, with area rivers
and streams gradually receding.

A widespread rainfall is expected for the middle of next week
with the possibility of moderate to heavy rain. Predictability
is low on rainfall amounts and hydrologic impacts at this time.


NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air.




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