Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 201957

Area Forecast Discussion
National Weather Service New York NY
357 PM EDT Fri Apr 20 2018

High pressure builds in from the west through tonight, then
remains over the region into Monday. A coastal low will likely
affect the region the middle of next week.


An upper longwave trough along the eastern Canadian coast and
extending into the northeast remains through tonight with a
northwest cyclonic flow. Meanwhile surface low pressure along
the Canadian coast tracks northeast as high pressure builds to
the west. The atmosphere will remain dry and cloud-free tonight.
Winds will be diminishing, and likely decouple late tonight.
This will allow for good radiational cooling with clear
conditions. Inland areas will likely see patchy to areas of
frost and included in the weather forecast. However, the Spring
frost/freeze program has not begun across these areas.


The upper trough remains across the northeast through Saturday
night as the center of the surface high builds into the
northeast. The weather will remain quiet and cloud free.
Cyclonic flow and weak cold advection continue through Saturday
night, however, the airmass will be modifying under full sun,
and highs Saturday will be approaching normal levels. Saturday
night will be cloud-free with light winds and again there will
be ideal radiational cool conditions. So, expect areas and
patchy frost inland.


Upper air pattern will very much resemble early springtime
as an upper low over the Mississippi Valley slowly works east
on the heels of a departing northern branch trough over the
Northeast. Ridging both aloft and at the surface builds across
the region to start the week but then gives way to the
aforementioned southern branch close low. The system will lift
northward in response to a northern branch shortwave trough
moving into the upper Midwest and Great Lakes, sending surface
low pressure up the eastern seaboard Tuesday into Wednesday.

Overrunning rains are forecast to develop across the area
Tuesday night and continue into Wednesday night. There are
some differences thereafter though with the global models as
the ECWMF is more progressive with this system and dries things
out for the end of week, while the GFS and GGEM close off the
northern branch trough with unsettled conditions lingering until
a cold frontal passage Friday night. Thus, will maintain a
low chance of showers for the end of the week. The point to be
made here there is clearly uncertainty in the guidance for the
end of the week as northern branch shortwave energy dives
southeast across the Upper Midwest and Great Lakes region.
however, all the global models are pointing to amplification of
the ridge out west and the trough reestablishing itself across
the east by next weekend.

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 builds in from the west tonight through Saturday
morning, before settling over the region into Saturday afternoon
and evening.

VFR through the TAF period.

Winds abate this evening, with speeds decreasing to around 10kt.
City and coastal terminals will lose their gusts shortly after 0z,
with inland terminals a few hours sooner. Winds will range around 10
kts late Saturday morning and afternoon. Wind direction will start
off NW on Saturday, before becoming more westerly towards the early
afternoon for the city terminals and some coastal terminals.

     NY Metro Enhanced Aviation Weather Support...

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

KJFK TAF Comments: Timing in gusts ending may be off by +/- 1 to 2
hours this evening.

KLGA TAF Comments: Timing in gusts ending may be off by +/- 1 to 2
hours this evening.

KEWR TAF Comments: Timing in gusts ending may be off by +/- 1 to 2
hours this evening.

KTEB TAF Comments: Timing in gusts ending may be off by +/- 1
to 2 hours this evening.

KHPN TAF Comments: Timing in gusts ending may be off by +/- 1
to 2 hours this evening.

KISP TAF Comments: Timing in gusts ending may be off by +/- 1
to 2 hours this evening.

.Saturday...VFR. NW-W winds.
.Sunday through Tuesday...VFR.
.Tuesday night through Wednesday...Sub VFR conditions
increasingly likely Tuesday night and into Wednesday.


High pressure continues to build into the waters from the west
with the pressure gradient force gradually weakening. Seas on
the ocean waters have subsided to below SCA levels. Also, winds
and gusts were generally below SCA levels, especially across
the open ocean waters. However, through early this evening
occasional nearshore gusts may reach 25 KT. With frequent gusts
and seas below SCA levels the SCA was cancelled.

High pressure will be across the forecast waters Saturday and
Saturday night with winds and seas remaining below SCA levels.

Tranquil conditions are forecast Sunday through Tuesday as high
pressure builds across the waters. However, 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 early next week.

A widespread rainfall is expected for the middle of next week
with the possibility 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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