Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 242349
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
749 PM EDT Fri Mar 24 2017

.SYNOPSIS...
A cold front over southern Canada will drift south through the
Tri-State Region on Saturday. An unsettled weather pattern
continues Sunday into the middle of next week. Cold front to our
south returns to the region Sunday night into Monday and moves
offshore Monday night. Another frontal system approaches on
Tuesday and moves across Tuesday night into Wednesday. High
pressure returns Thursday ahead of the next front on Friday.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Mid and high level clouds will remain through the overnight with
a few breaks from time to time. Temperatures vary drastically
in the SW flow this evening, which is common in the early spring
due to the cold nearshore waters. Parts of the NYC metro are in
the mid and upper 50s, while most locations were in the mid
40s. Temperatures will fall slightly overnight and then level
off. Lows will average 10 to 15 degrees above normal due to the
SW flow and cloud cover.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
A cold front over southern Ontario will track south through the
area by late Saturday morning into the afternoon. The timing is
pretty consistent between the NAM and GFS, so the NAM was used
in the grids. This translates into falling temperatures across
the northern half of the forecast area by afternoon, with the
fall in temperatures later in the day across New Jersey zones.

Water vapor indicates a moisture stream from the subtropical
Pacific into the Southeastern United States. This will allow for
some deeper moisture to penetrate into the region during the day
and through the night. The upper jet will be passing from
southern Canada into Northern New England at this time,
producing some broad lift. With these factors combining, light
rain has been forecast for the area mainly Saturday afternoon
and Saturday night. Easterly component low level flow could
allow for some fog or drizzle development particularly
overnight. Patchy fog has been maintained in the forecast along
with the light rain as a result.

The downscaled NAM was used for temperatures Saturday to account
for the cold frontal passage. A blend of guidance was used
Saturday night.

There is a low chance that temperatures approach freezing late
Saturday night which could result in some pockets of interior
icing. The probability is low at this time, so it has not been
included in this forecast.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Unsettled, progressive weather pattern will persist from Sunday
through the upcoming week. Deterministic models and ensembles are in
general agreement with the synoptic scale, with differences arising
in the timing and amplitude of several shortwaves to move across.

Backdoor front will be well to the south on Sunday with high
pressure building south of out of Quebec. Warm air overrunning the
stable, cool layer at the surface will keep low clouds throughout
the day and the chance for light rain or drizzle.
Upper level ridging will be in place, so there is not much support
for widespread precipitation. Temperatures will be held down in the
lower and middle 40s due to onshore flow and cloudy conditions.

Cutoff low over the central states on Sunday will open and lift
towards the Great Lakes Sunday night and then continue to dampen out
as it moves towards the region on Monday. Upper ridge axis gradually
moves offshore allowing for better lift for more widespread
rainfall. Pops increase to likely for much of the area late Sunday
night into Monday morning with categorical across the north closer
to the shortwave energy and best lift.
Shortwave axis quickly moves east Monday afternoon and evening,
which will take the lingering front to the south and east.

Brief ridging moves across Monday night with another shortwave on
its heels for Tuesday. This is where deterministic runs and
ensembles begin to diverge further as the latest 12z ECMWF flattens
this next shortwave out as it passes whereas the 12z GFS and the
GEFS are more amplified, bringing a weak low pressure across the
region. Have capped pops off in the chance range due to the
uncertainty on the amplitude of this wave. In either case, mostly
cloudy to overcast skies continue.

An amplifying shortwave across southeast Canada sends a shortwave
across New England on Wednesday, but frontal boundary should be well
offshore at this time, so improving conditions are expected. High
pressure than follows on Thursday before another frontal system
approaches for Friday.

Near seasonable temperatures are forecast on Monday with
temperatures returning to above normal levels Tuesday into
Wednesday. Seasonable temperatures are currently expected for the
end of the week.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
A cold front approaches from the north tonight, then presses to
the south Saturday morning. High pressure then builds down from
the north into Saturday evening.


VFR through at least 6z. MVFR conditions develop late
tonight/Saturday morning from N-S across the Tri-State. IFR
conditions develop Saturday afternoon, with patchy LIFR
conditions possible.

S winds at 10 kt or less become SW tonight, then light and
variable throughout by 12z. N then NE winds develop Saturday
afternoon, with speeds around 10 kt at city/Long Island
terminals and less than 10 kt elsewhere.

     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: High confidence of MVFR or lower beginning
midday Saturday. Timing in changes in wind speed and direction,
and ceiling could be off +/- 1-2 hours.

KLGA TAF Comments: High confidence of MVFR or lower beginning
midday Saturday. Timing in changes in wind speed and direction,
and ceiling could be off +/- 1-2 hours.

KEWR TAF Comments: High confidence of MVFR or lower beginning
early Saturday afternoon. Timing in changes in wind speed and
direction, and ceiling could be off +/- 1-2 hours.

KTEB TAF Comments: High confidence of MVFR or lower beginning
midday Saturday. Timing in changes in wind speed and direction
could be off +/- 1-2 hours.

KHPN TAF Comments: High confidence of MVFR or lower beginning
late Saturday morning. Timing in changes in wind speed and
direction, and ceiling could be off +/- 1-2 hours.

KISP TAF Comments: High confidence of MVFR or lower beginning
late Saturday morning. Timing in changes in wind speed and
direction, and ceiling could be off +/- 1-2 hours.

.OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...
.Saturday night-Monday...IFR likely with LIFR or lower
possible.
.Monday night-Tuesday night...MVFR or lower possible.
.Wednesday...becoming VFR. NW winds G15-20kt possible in the
afternoon.

&&

.MARINE...
Southerly flow will continue to gust into the early evening on
the ocean waters. Small Craft Advisory conditions will continue
on the ocean through Saturday despite the diminishing winds. It
is possible conditions remain at Small Craft Advisory levels on
the ocean Saturday night.

Marginal SCA winds are forecast on Sunday on the ocean, but seas
will likely be around 5 ft through the evening. From Sunday night
through Monday night, sub-sca conditions are forecast with an
overall weak pressure gradient. Seas may build to around 5 ft on
Tuesday as a cold front passes through. Otherwise winds and seas
should remain below SCA levels into Wednesday.

&&

.HYDROLOGY...
Less than a quarter inch of rain is expected through Saturday
night. Unsettled conditions Sunday through the middle of next
week will bring periods of rain. However, no hydrologic concerns
are anticipated at this time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ350-353-
     355.

&&

$$

SYNOPSIS...12/DS
NEAR TERM...DW/12
SHORT TERM...12
LONG TERM...DS
AVIATION...Maloit
MARINE...DW/12/DS
HYDROLOGY...12/DS


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