Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 191941
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
341 PM EDT Fri Apr 19 2019

.SYNOPSIS...
Low pressure slowly approaches tonight and Saturday from the
west. This slow moving system does not exit until the beginning
of next week. A cold frontal passage is expected during the
middle of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Longwave trough closes off, then cutoff low over southern states
makes slow progress northeast tonight. Deep surface low pressure
over the southern Appalachians moves northeast, but weakens slightly
overnight. Deep southerly flow, strong WAA and elevated instability
will set the stage for increasing coverage of showers, with thunder
possible as well.

Very warm air advects northward and patchy fog is possible
tonight in spite of strong south winds. Temperatures will fall
slightly this evening, then remain nearly steady overnight. Will
maintain the Flash Flood Watch. Convection should result in
local higher amounts, whereas other locations could see under an
inch.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Stacked low makes very slow progress east, and sfc low will weaken
quite a bit per model consensus during this time frame.

Convection over the area in the morning is expected to make eastward
progress during the day and into the night. Spotty showers remain a
possibility behind the main area of showers behind the higher
coverage in the afternoon and at night.

Do expect thunder chances in the morning with the main area of
convection. A midlevel dry slot will quickly move across the
area suppressing convection to the west closer to the upper low
center.

With clouds in place, low level inversion should preclude widespread
readings in the 70s, unless more sunshine is realized in the
afternoon. Did lean toward the higher end of guidance just in
case, but strong southerly flow will keep eastern areas
(particularly srn CT and LI) much cooler.

South winds weaken late in the day and at night, and temps should
remain quite mild in the 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Early in the period the upper level portion of the storm that
impacts the region in the near and short term portion of the
forecast will be over the region. Looking for a general shower
chance to begin the period with a closed upper level feature which
is progged to gradually fill, weaken, and lift out by Monday night.
Until then thought it best to keep general shower chance across much
of the CWA. With the upper level low over the area and some
instability present cannot rule out an isolated thunderstorm later
in the day on Monday, especially with any breaks of sun. In the wake
of the departing upper level system a brief period of soft ridging
will attempt to work in for late Monday night and into the day on
Tuesday. The thinking for Tuesday is to keep the region generally
dry with good agreement among the global models on timing.

The next system is progged to approach during Tuesday night and
early Wednesday. There could be enough energy aloft and enough low
level moisture to at least bring a period of chance showers to the
region for Tuesday night into Wednesday morning. There may be enough
instability depending on timing / time of day on Wednesday that a
thunderstorm or thundershower cannot be ruled out. Most of the
modeling has been consistent with the timing of this feature, with
the German ICON model having a few runs with precip hanging in for a
part of Thursday. This is at odds for the most part with the other
global deterministic models and mass fields, therefore will keep
Thursday dry for now with high pressure building in. WPC discussion
does however point out uncertainty next week with individual
shortwaves tracking across the Midwest into the Northeast. This has
lead to variability among the various global ensemble suites. So
confidence is lower than desired for later next week.  For now have
leaned towards high pressure being in control by late Wednesday or
Wednesday night through much of Friday as the NAEFS 500 mb forecast
suggests an increase in progression with the northern branch.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
A slow moving low pressure system will impact the airspace through
the weekend.

Mainly VFR through the early evening, with occasional MVFR cigs
possible. Brief/occasional showers may also temporarily lower
ceilings/visibilities. Conditions then deteriorate further tonight
to IFR-MVFR as steadier rain arrives after the evening push. The
heaviest rain is expected towards daybreak, with embedded
thunderstorms possible for the morning push. The line will slowly
move east of the terminals into the early afternoon. It is possible
isolated thunderstorms develop again in the afternoon, but in
general as the heavier rain departs, conditions should improve with
only occasional light rain across the area.

Winds will remain an issue through the TAF period, generally
sustained from the south around 15-20kt, and higher gusts more
likely this evening, and then again tomorrow as the heavier rain
departs. There will be a prolonged period of LLWS for all sites
except KSWF, but more common for KLGA/KJFK and eastward.

Refer to the New York Center Weather Service Unit products for more
information about compression and route impacts due to thunderstorms
at www.weather.gov/zny.

  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: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

KLGA TAF Comments: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

KEWR TAF Comments: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

KTEB TAF Comments: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

KHPN TAF Comments: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

KISP TAF Comments: Timing of flight category changes may by off by
an hour or two. Winds may occasionally be stronger than forecast.

.OUTLOOK FOR 18Z SATURDAY THROUGH TUESDAY...
.Saturday...MVFR or lower in occasional showers. LLWS ending. Winds
decrease into Saturday night.
.Sunday...MVFR or lower in a chance of showers.
.Monday...MVFR or lower in a chance of showers.
.Tuesday...VFR. Slight chance of showers late in the afternoon.
.Wednesday...MVFR or lower possible in showers.

&&

.MARINE...
Strong southerly winds will continue tonight, 20-30 kt, ahead of low
pressure. These winds will slowly diminish Saturday, likely falling
below 25 kt threshold for SCA during the afternoon. These southerly
winds diminish further at night as the pressure gradient relaxes,
with weakening low pressure to the west.

Ocean seas will remain rough through Saturday night, so SCA will
remain up through that time.

Southerly flow diminishes Saturday night into Sunday as low pressure
weakens as it approaches the waters. With the diminished flow with
low pressure over the coastal waters a period of patchy fog may
occur for late Saturday night into early Sunday morning. Seas will
remain up on the ocean waters due to a south to southeasterly swell,
therefore SCA conditions will continue through the weekend and into
early next week on the ocean waters. Meanwhile, sub SCA conditions
are expected for the non-ocean waters through the early part of next
week. Sub SCA conditions may finally return by Tuesday afternoon on
the ocean waters as seas subside below 5 ft.

&&

.HYDROLOGY...
Rain totals tonight and Saturday should range from a half an
inch in spots, to locally 2 inches, with the best chance for
higher QPF east of NYC into Srn CT and LI. Due to high
precipitable waters, deep southerly flow, and lift, the flood
watch remains in effect.

Otherwise, no hydrologic impacts are expected for the second
half of the weekend into the end of next week.

&&

.TIDES/COASTAL FLOODING...
The evening/night high tide cycle is the astronomically higher
of the two. Minor tidal flooding is possible on the usually
most vulnerable south shore bays of Queens and Nassau Counties
during this time. Elsewhere, a statement has been issued for
localized coastal flooding. This is for western LI Sound, except
NYC and LI, and the lower NY Harbor.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) remains off
the air.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Flash Flood Watch from 2 AM EDT Saturday through Saturday
     evening for CTZ006>008-010>012.
     Flash Flood Watch from 2 AM EDT Saturday through Saturday
     afternoon for CTZ005-009.
NY...Flash Flood Watch from 2 AM EDT Saturday through Saturday
     evening for NYZ078>081.
     Flash Flood Watch from 2 AM EDT Saturday through Saturday
     afternoon for NYZ067>075-176>179.
     Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for
     NYZ178-179.
NJ...Flash Flood Watch from 2 AM EDT Saturday through Saturday
     afternoon for NJZ002-004-006-103>108.
MARINE...Small Craft Advisory until noon EDT Saturday for ANZ330-335-
     338-340-345.
     Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355.

&&

$$
SYNOPSIS...JE/PW
NEAR TERM...PW
SHORT TERM...PW
LONG TERM...JE
AVIATION...MD
MARINE...JE/PW
HYDROLOGY...JE/PW
TIDES/COASTAL FLOODING...PW
EQUIPMENT...


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