Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 220440
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1140 PM EST Sun Jan 21 2018

.SYNOPSIS...
A warm front will approach the region tonight, slowly working
north through the region late Monday night into Tuesday morning.
A cold front then follows later on Tuesday. High pressure
returns for Wednesday through Friday. The high moves east to
start the weekend ahead of the next cold front.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Only minor updates needed to account for temperature trends
across the pine barrens of Long Island, where initially cool
temperatures are now beginning to rise as thick cloud cover
spreads east.

Temperatures under overcast conditions are holding nearly
steady, or slowly rising. Areas of light rain were breaking out
across northeastern PA into CT, as isentropic lift increases
with the development of a warm frontal boundary.

A warm front approaches from the south tonight and likely
remains just offshore. Ahead of this front, increasing moisture
and lift bring chances of PCPN across the area. The moisture is
somewhat shallow, so a light rain or drizzle is be expected. The
majority of the area will have temperatures above freezing
coinciding with the rain/drizzle chances, however portions of
interior CT and the Lower Hudson Valley could have freezing
temperatures. Temps aloft are too warm for snow and likely too
warm for any chance of sleet, so freezing rain/drizzle could
happen for these northern areas. Coverage and likelihood for
freezing rain is not high enough for any advisory at this time,
and will continue to address this threat with the HWO and SPSs
as needed.

Cloud cover and weak warm advection will result in a non-diurnal
temperature trend for tonight. Rising dewpoints should also produce
at least patchy fog across most of the area.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
The warm front remains just offshore or potentially shifts into some
of the southern zones during Monday. The moisture profile doesn`t
change all that much, so PCPN chances remain through the day. Model
consensus has higher PoPs towards the north and east and with SW
zones potentially dry during the afternoon. Still a threat early on
for freezing rain/drizzle across some northern zones, otherwise
temps warm into the 40s with even some 50s across parts of the city
and NE NJ.

Low pressure heads into the Great Lakes Region with a cold front
advancing into central PA by late Monday night. The warm front
probably remains just south of us or across some of the southern
zones. It will have a better chance of advancing north when a 60-70
kt low level jet pushes in from the south Tuesday morning. The cold
front then passes through during the afternoon.

Moisture deepens as a theta-e ridge shifts in late at night into
Tuesday morning. Strong lift will be available as well with the llj,
cold front, and synoptic lift from a 200-300 mb jet streak. Rain
becomes likely late at night into Tuesday morning and ends for all
but perhaps eastern LI and SE CT by sunset. Can`t completely rule
out a rumble or two of thunder with strong lift and a little CAPE
right ahead of the cold front, but will leave a mention of it out of
the forecast for now. Rain however may still by heavy at times on
Tuesday with the cold front passage. No flooding headlines
anticipated based on guidance and expected rainfall totals.

Despite a low level inversion, a period of 30 to 40 mph gusts
appears likely for LI/SE CT Tue late morning into afternoon ahead of
the cold front as the llj passes through. There`s a low chance for a
few gusts of 40 to 50 mph being mixed down should there be any
convection/heavy rain. No wind headlines at this time given the low
likelihood of a widespread event and it being a 4th period event.

Another day of above-normal temperatures expected for Tuesday, with
near-record warmth for KJFK, KISP and KBDR. Highs generally in the
50s across the region.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Relatively quiet and dry long term period is anticipated as mean
upper trough Wednesday into Thursday gives way to upper ridging
Friday into the first half of the weekend. The flow pattern remains
progressive across the CONUS with the next upper trough and
shortwave approaching for next weekend. Deterministic and ensemble
means are in overall good agreement in the above scenario, with
diverging solutions regarding the trough/cold front next weekend.

Initial shortwave moves offshore Tuesday night which quickly takes
the cold front impacting the region on Tuesday with it as well. This
should help carve out a large upper trough over the eastern Seaboard
later Wednesday into Thursday. The temperatures behind the front
will only fall to near/slightly above seasonable levels Tuesday
night and Wednesday. As the mean upper trough takes shape Wednesday
night into Thursday, a resurgence of colder air is advected
southward with Canadian High pressure building towards the Tri-
State. Temperatures on Wednesday night fall into the teens inland to
the lower 20s closer to the coast. Below normal temperatures in the
lower 30s are forecast for Thursday. Breezy conditions should also
prevail both Wednesday and Thursday as the region will lie between
low pressure to our NE and building high pressure to the west.

The high pressure briefly settles over the region on Friday as upper
ridging builds overhead. Below normal temperatures continue with
highs only a few degrees warmer than Thursday.

Much milder conditions quickly return for next weekend. Temperatures
should warm well into the 40s for Saturday and possibly the 50s on
Sunday ahead of the next cold front. Model guidance is slowly
converging on the timing of the front, but this is seven days out so
have elected to hold PoPs in the chance category with a PTYPE of
rain.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Deepening low pressure across the central US tracks northeast
overnight through Monday. A warm front develops and then approaches
from the southwest overnight. The warm front then moves slowly
through the region during Monday with the timing and placement
uncertain. At this time the warm front is timed through the NYC
metro terminals late in the afternoon, around 21Z. The front may
stall in the vicinity of Long Island Sound and the CT coast.

MVFR conditions develop overnight with drizzle, light rain, and fog.
Early Monday morning conditions inland likely lower to IFR as the
warm front moves farther to the north. In the NYC metro area the
warm front may move through late Monday afternoon with VFR
conditions developing. Inland MVFR and possible IFR conditions
remain through the afternoon with a brief improvement possible
early in the evening.

Winds will be light and variable to near calm through most of the
forecast, becoming S to SE less than 10 kt in the NYC metro behind
the warm front.

.OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
.Monday night...VFR NYC metro terminals early, then becoming IFR
toward 06Z. Long Island and northern terminals MVFR to IFR. LLWS
developing toward 12Z. Showers become likely west after 06Z.
.Tuesday...IFR/LIFR in SHRA, isolated TSTM possible. LLWS. S winds
G25-30KT.
.Wednesday...VFR. WNW G20-25KT.
.Thursday-Friday...VFR.

&&

.MARINE...
Winds and seas forecast on track. Updates were made to the
timing of precipitation and fog developing across the forecast
waters tonight. A warm front then approaches tonight and slowly
moves through some of the waters on Monday, keeping winds light
and seas tranquil. As the warm front heads farther north Monday
night into Tuesday, southerly flow will rapidly strengthen,
with at least SCA-level winds on the waters. A strong low-level
jet will lead to the possibility of at least isolated gale-force
winds on Tuesday, despite an inversion that may hinder the
strongest winds from reaching the waters. Seas will rapidly
build in response to the strengthened flow. A gale watch is
therefore in effect for the ocean waters, eastern LI Sound and
the LI Bays. A small craft advisory would probably be needed
elsewhere, but with this a 4th period event, will wait for new
guidance to finalize where SCAs and other gale headlines will be
issued.

There may be a brief drop off in winds on the waters Tuesday
evening as the cold front moves through. SCA gusts will return
quickly into Wednesday morning and then continue into Thursday
as the waters will be situated between low pressure to the north
and high pressure to the west. Winds on the LI Bays, LI Sound,
and NY Harbor may be a bit lower than on the ocean, especially
on Thursday, but could still gust close to 25 kt. Winds diminish
Thursday night into Friday as high pressure builds over the
waters. Highest ocean seas should occur Tuesday night into
Wednesday, before subsiding below 5 ft Wednesday night.

&&

.HYDROLOGY...
Total rain Monday night through Tuesday is expected to range mostly
1/2 to 1 inch, with locally 1 to 2 inches possible. No significant
hydrologic issues are anticipated at this time.

No hydrologic impacts are anticipated Wednesday through early next
weekend.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Gale Watch from Tuesday morning through Tuesday afternoon for
     ANZ330-340-345-350-353-355.

&&

$$
SYNOPSIS...JC/DS
NEAR TERM...JC/MD/DS/19
SHORT TERM...JC
LONG TERM...DS
AVIATION...19
MARINE...JC/DS/19
HYDROLOGY...JC/DS
EQUIPMENT...



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