Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 181811
Area Forecast Discussion
National Weather Service New York NY
111 PM EST Wed Jan 18 2017
-- Changed Discussion --Low pressure continues to work farther offshore and gradually
strengthens through tonight. Meanwhile weak high pressure will
build from the west tonight into Thursday, and settle overhead
Thursday night into early Friday. A weakening frontal system will
approach Friday night into Saturday, and then dissipate.
Strengthening low pressure will approach from the southwest from
Sunday into Monday while a gradually strengthening high builds
into the Canadian Maritimes. The low will continue to approach
Monday night into Tuesday while slowly weakening.
-- End Changed Discussion --
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Only minimal changes needed to the forecast to reflect current
temperature/dew point trends.
The 1010 mb surface low is southeast of Long Island as of 17z. As
a mid level low moves into the Mid Atlantic region, weak sfc
troughing and cyclonic flow should linger, maintaining overcast
skies and lingering light rain/drizzle, especially across
central/eastern Long Island where orographic lift of the nearly
saturated air mass will also come into play as sfc flow backs
Highs today should be from the upper 30s well inland, to the
lower/mid 40s elsewhere, per MAV/MET blend which was on the mark
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Low level moisture will remain trapped beneath an inversion, but
as shortwave mid level ridging passes across this evening behind
the mid level low moving out over the Atlantic, there could be a
break in any light rain/drizzle before another mid level
shortwave trough approaches and moves across NY and New England
after midnight. Still the possibility for some spotty light
freezing rain/freezing drizzle well inland as temps drop to the
upper 20s well inland, to the mid 30s across NYC metro and Long
Deep layer high pressure should return on Thu as this next
shortwave trough passes east. After any early to mid morning
clouds and patchy fog, afternoon sunshine and a drying downslope
NW flow should send temps into the lower 50s across NYC metro and
Long Island on Thu, with mid/upper 40s inland.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
In the mid to upper levels, a more amplified pattern is shaping
up starting Thursday night and going into early next week. There
will be intermittent influences from the upper level subtropical
jet, the most prominent being Sunday night through Monday night.
This is when jet stream speeds will be the highest on average.
At the surface, two frontal systems will be featured in the long
term making for the next chances of precipitation. The first being
Friday night into Saturday associated with a weakening frontal
system. These features essentially dissipate Saturday leaving the
region on the western side of a broad weak area of high pressure.
A stronger frontal system approaches late Sunday into early next
week with some more baroclinicity as evidenced from the sharpening
The winds pick up and set up an easterly fetch in response to an
increasing pressure gradient as a strengthening high pressure builds
southward from Southeast Canada and this strong frontal system
approaches from the Southeast U.S. The persistent fetch may lead to
some possible coastal flooding as we approach a new moon which will
be a few days later. Too soon to tell how much surge there will be
though. The high eventually traverses Nova Scotia and settles
southeast of there in the Northern Atlantic, keeping the region in
an easterly flow.
With a cool maritime airmass in place, there will be a low chance
of rain mainly on Friday night associated with the approach of the
first week frontal system. Amounts of rain forecast from this
look to remain under a quarter of an inch. The second stronger
frontal system will have both higher chances of rain plus larger
rainfall amounts due to the longer period of time of rain
forecast. Chances of rain begin mainly Sunday afternoon and will
be highest (mainly between 50-60 percent) on Monday and Monday
night. See hydro section for further details on this event.
Both of the aforementioned systems look to be mainly rainfall with
the setup and positioning of the forecast high and low pressure
areas. Across the interior areas, some mixing with sleet will be
possible late Sunday night into early Monday.
Temperatures during the long term look to remain above normal. Highs
mainly in the 40s except for Saturday and Tuesday when highs are
forecast more into the low 50s on average. Relatively coldest night
forecast is Thursday night when lows are forecast to range from the
mid 20s to mid 30s. Otherwise other nights in the long term are
forecast to have lows mainly in the 30s with NYC not deviating too
much from the 40 degree mark.
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --Offshore low pressure continues to work away from the terminals
through tonight, while high pressure works in from the west.
The theme will be gradual improvement through tonight as
widespread IFR cigs at the onset lift to MVFR this afternoon and
then VFR overnight. Areas of fog possible tonight.
N-NE winds this afternoon will gradually back to the N-NW through
tonight. Speeds around 10 kt or less expected, a bit higher at
the city terminals.
NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90
KJFK TAF Comments: Amendments likely for timing of improving
KLGA TAF Comments: Amendments likely for timing of improving
KEWR TAF Comments: Amendments likely for timing of improving
KTEB TAF Comments: Amendments likely for timing of improving
KHPN TAF Comments: Amendments likely for timing of improving
KISP TAF Comments: Amendments likely for timing of improving
.OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY...
.Friday night...Chance of MVFR or lower in -RA.
.Sunday...Chance of MVFR of lower in -RA, with best chance at
CT/Long Island Terminals.
.Monday...Chance of IFR with heavy rain and strong E-NE winds.
-- End Changed Discussion --
Surface winds have backed to a more north-northeasterly direction
as the low has now moved southeastward of Long Island. Gusts
20-25kt are currently being measured on the ocean waters. Seas are
rising in response, with 5+ ft seas spreading westward to all
ocean waters late today. These SCA conds should continue into Thu
afternoon, with some residual 5-ft seas still possible Thu
SCA conditions are possible on the ocean on Sunday, and for all
waters on Monday, with the approach of the next storm. Gales may
be possible on the ocean Monday afternoon/evening, and ocean seas
could reach 6-11 ft Sunday night into early next week as an
easterly fetch sets up.
For Sunday night into early next week, low pressure could bring a
significant rainfall of 1-2 inches. Some minor flooding may be
MARINE...Small Craft Advisory from 4 PM this afternoon to 6 PM EST
Thursday for ANZ355.
Small Craft Advisory until 6 PM EST Thursday for ANZ350-353.