Area Forecast Discussion
Issued by NWS Upton, NY

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018
FXUS61 KOKX 170108
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
908 PM EDT Wed Oct 16 2019

.SYNOPSIS...
Rapidly deepening low pressure lifts north across the area this
evening and then tracks slowly across New England late tonight
through Thursday. High pressure will build into the region Friday,
remaining through the weekend. Another frontal system affects
the area Monday night through Tuesday, followed by high
pressure for the mid week.

&&

.NEAR TERM /THROUGH THURSDAY/...
Low pressure currently over southern New Jersey will continue to
rapidly intensify as it ejects off the coast. Steady heavy rain
has transitioned to more in the way of showers, with the back
edge of the precipitation already moving through central New
Jersey. Therefore, have lowered POPs across the area, as well as
QPF amounts somewhat, given the faster progression of the
system. There still remains a slight chance for thunder,
especially eastern sections.

This system will feature a coupling upper jet structure, as a
frontal wave undergoes explosive coastal development this
evening into the overnight. Models are in good agreement with
the overall evolution and track with subtle timing and intensity
issues. The southern branch jet energy pivoting off the Mid
Atlantic coast this evening takes the upper trough negative and
eventually closes off a new upper low across New England by
morning.

Moderate to heavy frontal band rains will work across the area
for the first half of tonight and then transition to comma head
rains as the low wraps up. This will result in widespread
rainfall amounts of 1 to 2.5 inches, but possibly as high as 3
inches in banded rain to the north and west of the low track.
The low has continued to trend north and west the last couple of
days, with the operational suite now in close agreement of a
track across western sections of Long Island and Connecticut.
This would keep the axis of heaviest rainfall across the Lower
Hudson Valley, SW CT, and northeast NJ. Still though, the
frontal band, subtrop moisture, and anomalous upper jet (3 to 4
SD), all point to heavy rain both with the warm conveyor belt
ahead of the deepening low and in the wraparound.

Gridded FFG values for NE NJ are 2 to 2 1/2 inches. Thus, a
flash flood watch remains in effect for NE NJ. Elsewhere, there
is a lower probability of flash flooding for urban, poor
drainage, and low lying areas.

Comma head rains may linger across northern portions of the
Lower Hudson Valley and interior southwest CT several hours
longer.

Additionally, a robust LLJ on the front end and back side of
the low this evening may briefly produce 40 to 50 kt gusts. The
best chance may be on the back side of the low with a sting jet
signature. A prolonged wind advisory level event then follows
for the remainder of the night into Thursday with frequent gusts
up to 40 kt. Thus, a wind advisory is in effect for the entire
area.

Cold advection and cyclonic flow will keep plenty of clouds
around on Thursday. There will also be some scattered low-top
showers with steep low-level lapse rates.

Overnight lows will range from the upper 40s to lower 50s,
generally a few degrees above normal. Highs on Thursday will
below normal behind the low with the cold advection, ranging
from the mid 50s to around 60.

&&

.SHORT TERM /THURSDAY NIGHT/...
Low pressure over northern New England will gradually weaken as
it lifts up into the Canadian Maritimes. As a result, winds
will gradually subside through the night, but still gusting 20
to 30 mph. Lows will generally be in the 40s, fairly homogeneous
with the airmass remaining well mixed.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Low pressure continues to move away from the area, moving into the
Canadian maritimes, while high pressure builds into the area on
Friday. There will continue be a strong pressure gradient between
the low and incoming high, so conditions will still be rather
breezy, with winds diminishing in the afternoon. Gusts of 25 to 30
mph are possible.

A northwest flow will keep temperatures near or just below normal
across the area on Friday, with highs in the upper 50s to around 60.
Similar temperatures are expected on Saturday.

Mainly dry conditions expected with high pressure moving overhead
and offshore over the weekend. The one concern is that the GFS is
developing an area of low pressure off the coast of the Carolinas,
then heading northeast. Although this is an outlier, there is enough
uncertainty to have low end slight chance POPs across most of the
tri-state. The forecast area will be on the northern fringe of this
possible storm, also warranting slight chance POPs.

This coastal low is reflected in the ECMWF and Canadian, however, it
makes little headway over the southeast U.S., but the retreating
high noses back into the area, keeping the area mostly dry through
Sunday night. The ECMWF does bring in some precipitation on the
northern fringe Sunday night, so although dry right now, slight
chance POPs are possible Sunday night.

A more potent system may impact the area Monday into Tuesday, with a
period of moderate to briefly heavy rain. It is too far out to pin
down any details at this time.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
***HIGH IMPACT RAIN AND WIND EVENT INTO THURSDAY***

Intensifying low pressure over central NJ will pass through
tonight. Mostly IFR conds north/east of the low, E-SE winds
G30-40kt along the coast, and LLWS with SE winds 50-60 kt at
FL015-020 will give way overnight to VFR conds and NW then W
flow G30-35kt, though MVFR cigs may persist 1-2 hr after rain
ends (04Z-05Z NYC metros).

BKN VFR cigs and W winds G35-40kt possible Thursday late AM and
afternoon, along with chance of a shower with brief MVFR conds
mainly NE of the NYC metros.

.OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...
.Thursday night...BKN VFR cigs. WNW winds G25-30kt in the
evening, then 20-25kt overnight.
.Friday...VFR. NW winds G20-25kt.
.Saturday...VFR.
.Sunday and Monday...Mainly VFR.

&&

.MARINE...
A rapidly developing coastal low will track across the waters
this evening and up into New England tonight. This will result
in a prolonged period of gales. There could even be a brief
period of storm force gusts just ahead of and behind the low
this evening. Winds are forecast to drop below Gale to SCA late
Thursday night.

SCAs should continue into Friday as gusts of 25 to 30 kt are
possible across all waters on Friday as a strong pressure gradient
will be present due to the departing coastal storm and building high
to the west. Winds diminish Friday afternoon into Friday evening. 5
to 7 ft waves on Friday on the ocean waters also diminish, coming
below 5 ft Friday night.

Winds and seas remain below SCA through Monday with high pressure in
control. A complex frontal system approaches Monday, with an
increased east to southeasterly flow developing. This will allow
waves to build on the ocean to 5 to 8 ft over the ocean waters
Monday night. Gusts of 25 to 30 kt are also possible Monday night.

&&

.HYDROLOGY...
A quick shot of heavy rainfall this evening into early Thursday
morning will produce rainfall amounts of 2 to 3 inches, with
localized swaths of 2-4 inches possible. The bulk of the
rainfall is expected in a 6-8 hr period.

Urban, poor drainage, and low lying flooding is expected. There is a
low probability of flash flooding along a few of the fast responding
small rivers and streams in NE NJ and the Lower Hudson Valley if the
higher rainfall amounts are realized.

Additionally, localized flash flooding will also be an issue for
coastal roads if heaviest rain coincides with the Wed night high
tides.

&&

.TIDES/COASTAL FLOODING...
Gale force, borderline storm force, E/SE winds this evening
will have surge rapidly increasing to 2 1/2 to 3 1/2 ft above
astronomical tides this evening.

These elevated water levels with breaking waves of 3 to 5 ft
will present a heightened threat of widespread moderate coastal
flooding (inundation of 2-3 ft above ground level) for SW CT
and S Westchester. Flooding of some roadways and vulnerable
structures behind protective dunes and seawalls is likely.

Elsewhere minor to locally moderate coastal flooding (inundation
of 1-2 ft above ground level) is expected for LI, Queens,
Bronx, and SE CT.

Along the Atlantic ocean beach front, high surf should peak at
8-12 ft this evening, which will result in significant beach
erosion and areas of erosion to dune structures during the times
of high tide tonight, with some flooding of shoreline roadways
and vulnerable structures.

Additionally, if the heaviest rain coincides with the high tide
tonight, more widespread flooding could be experienced than would
normally be expected.

With gusty westerly and mainly offshore flow on Thursday, for the
next high tide cycle for Thursday morning, no coastal flooding is
expected.

&&

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

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory until 6 PM EDT Thursday for CTZ005>012.
     Coastal Flood Warning from midnight tonight to 4 AM EDT
     Thursday for CTZ009-010.
     Coastal Flood Advisory until 2 AM EDT Thursday for CTZ011-012.
NY...Wind Advisory until 6 PM EDT Thursday for NYZ067>075-078>081-
     176>179.
     Coastal Flood Advisory until 4 AM EDT Thursday for NYZ073-
     078>081-176-177.
     Coastal Flood Warning from midnight tonight to 4 AM EDT
     Thursday for NYZ071.
     Coastal Flood Advisory until 2 AM EDT Thursday for NYZ178-179.
NJ...Wind Advisory until 6 PM EDT Thursday for NJZ002-004-006-
     103>108.
     Flash Flood Watch until 4 AM EDT Thursday for NJZ002-004-006-
     103>108.
MARINE...Gale Warning until midnight EDT Thursday night for ANZ330-335-
     338-340-345-350-353-355.

&&

$$
SYNOPSIS...JP/DW
NEAR TERM...JP/DW
SHORT TERM...DW
LONG TERM...JP
AVIATION...Goodman
MARINE...JP/DW
HYDROLOGY...JP/DW
TIDES/COASTAL FLOODING...
EQUIPMENT...



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