Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 220557
Area Forecast Discussion
National Weather Service New York NY
157 AM EDT Sat Apr 22 2017
Low pressure over southern Canada will continue to move east
overnight, dragging an occluded front across the area. High
pressure then slowly builds in from the west on Saturday before
building across the area on Sunday and then offshore on Monday.
A wave of low pressure will move off the Southeast coast Monday,
and track slowly north through midweek. High pressure will
build back in for the end of the week.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Visibilities have lowered to around 1 SM with patchy areas under
1 SM, however, do not expect visibilities to drop to a quarter
of a mile or less, so no dense fog advisory for the coastal
areas. There were areas of drizzle and expected to be possible
through 08Z, so added to the forecast.
As the primary low continues to move east across southern
Canada, it will drag an occluded front across the area
overnight. A weak low along a warm front passes south of Long
Island overnight. This has resulted in light northerly winds,
which seems to have kept visibilities from falling as much as
With plenty of low level moisture and light winds, patchy to
areas of fog, locally dense, is still possible overnight. High
res models still indicate that fog/visibilities improve by
daybreak as slightly drier air begins to work into the region.
Temperatures will a few degrees, into the mid 40s to around 50,
several degrees above normal.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
With high pressure gradually building into the region from the
west, Saturday should remain dry. Rain should stay just south
during the day. Northwest flow will allow for some mid-level
drying during the day, leading to at least periods of sunshine.
Temperatures will rise into the low 60s, near normal for this
time of year, before falling into the mid 40s at night.
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A split upper flow across the Eastern U.S. will feature a
departing shortwave trough across the Northeast at the onset of
the period, with an anomalously far south closed low moving
into the southeast. The latter of which will likely bring some
inclement weather to the area for the first half of next week.
High pressure will initially be in place Sunday into Monday
with some uncertainty to the northern extent of the rain shield
during this time. A confluent upper flow will reside across the
area at the start of the period, with a deep layered W/SW flow
converging with the northern branch of the polar jet. Initial
thinking is this should keep the area under subsidence and
drying, but any shift in this zone could bring light rain/clouds
in sooner. The best timing for a steady rain appears to be
Monday night through Tuesday night as the upper low moves
offshore and warm, moist air overruns the region. This mainly
appears to be an overrunning rain event. Up to an inch rainfall
seems to be a reasonable possibility at this time.
High pressure follows Wednesday night into Thursday with model
differences on the amplitude of a deepening western trough and
the ridging east of the Mississippi River Valley. A weakening
cold front works across the area on Thursday per the GFS and
GGEM, while the ECMWF dissipates it to the west. Leaned toward
the ECMWF at this time, but these details are far too early to
As for temperatures, near seasonable levels through mid week, if
not a bit cooler during the daytime due to cloud cover and rain.
A significant warmup is possible for the end of the week with
warming heights aloft.
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --A wave of low pressure along a nearly stationary frontal
boundary tracks south of the terminals through this afternoon.
High pressure builds in from the west late today into tonight.
IFR/LIFR conditions are expected to continue through around 09z
with with eastern terminals holding a few hours longer.
Conditions then improve to MVFR before gradually improving
to VFR around 15z at city terminals and around 17-18z at KISP,
KBDR, and KGON. Timing of improving conditions in the TAFs may
be off by 1-2 hours. There is also a possibility MVFR
conditions hold longer into the day than currently forecast.
There is a chance of light rain after daybreak through early
afternoon mainly at coastal terminals, but confidence is not
high enough at this time to include in TAF and visibilities
should remain VFR.
Light N-NNE winds early this morning will gradually back to the
NW today. Speeds should remain around 10 kt or less. Winds will
stay to the right of 310 magnetic at city terminals. NW winds
.OUTLOOK FOR 06z SUNDAY THROUGH WEDNESDAY...
.Monday...VFR during the day. Chance MVFR in rain at night.
.Tuesday...Chance IFR in rain. NE gusts 20-25 KT near coast
.Wednesday...MVFR possible early, becoming VFR.
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Ocean seas have increased, mainly in an easterly swell, with
buoys 44025 and 44017 near and just over 5 FT. This should be
short lived however. Will hold off on SCA issuance as conditions
improve with weakening winds.
A Dense Fog Advisory remains in effect across much of the
eastern waters as fog and low visibilities persist. Western LI
Sound was included in the advisory earlier. Fog should become
more patchy in nature early Saturday morning before finally
clearing by daybreak.
Winds back and lighten to the N/NE overnight.
A generally weak pressure gradient will result in winds 15 kt or
less late tonight through Saturday night as high pressure
builds into the region.
High pressure over the waters will result in sub-sca conditions
Sun into Mon. A low pressure system moving off the southeast
coast Monday will track slowly north through midweek. A
prolonged and increasing easterly flow will set up from Monday
night into Wednesday. There may be a period of gusts approaching
small craft levels on the ocean waters Tuesday and Tuesday
night. However, with the easterly flow, ocean seas are expected
to build to small craft levels by late Monday night and remain
into Wednesday. As the low tracks through the forecast waters
and weakens Wednesday winds will remain below small craft
levels, but seas will be slow to subside below small craft.
Up to an inch rainfall seems to be a reasonable possibility
Monday night into Wednesday. No hydrologic impacts are
anticipated at this time.
MARINE...Dense Fog Advisory until 4 AM EDT early this morning for