NYC Office Forecast Discussion

000
FXUS61 KOKX 211342
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
942 AM EDT Thu Mar 21 2019

.SYNOPSIS...
Low pressure will approach from the south through Thursday, and
pass through late Thursday night, then intensify as it moves
slowly northeast toward the Canadian Maritimes Friday into
Saturday. High pressure builds to the south and west Saturday
night through Sunday. The high will give way to a cold front on
Monday. High pressure returns Tuesday into Wednesday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast generally on track early this morning. Rain is
beginning to overspread southern and central NJ, and this should
continue working north through the morning. Any returns on radar
east of the city have been light and have shown a general
weakening trend as they encounter stronger surface ridging.

Otherwise, two shortwaves will phase this morning leading to
the development off low pressure along the Mid Atlantic coast.
An axis of moisture convergence emerging north from the low and
a developing SE flow will yield good frontogenesis in the low
and mid levels with the enhanced lift waiting until the mid
level energy begins to work in tandem with the lower level warm
air advection. After collaboration with surrounding offices have
decided to hold off on any Flood Watch, with the concern here
mainly for far western areas, like Rockland County with lower
FFG values, and Northeastern New Jersey counties also with lower
FFG. The thinking right now is that the duration of moderate to
potentially heavy rain will not be long enough in duration
because of the fast movement of the system. The day shift will
have to monitor however, as there is higher res guidance that
does concentrate a slug of moderate to heavy rain either over,
or just west of our western most sections. If any heavier
thundershowers develop then flooding cannot ruled out, but the
thinking now is due to a lack of confidence in enough of a
heavier rainfall duration that any flooding will likely more of
the nuisance and poor drainage variety.

The latest guidance does hold off on any appreciable rain for
eastern and northeastern sections until after 21z or so. This is
when the impacts from a strong LLJ may be felt which will aid
lift and could very well produce some heavier rain bands, with
possible embedded thunder into the early evening for LI and CT.
Thinking a good half inch to an inch of QPF for the eastern
half of the area, with areas west of NYC getting a solid an inch
to inch and a half. There is very good agreement amongst the
global and high res models with respect to the QPF drivers,
placement of dynamics and best thermal advection. This leads to
relatively good agreement with the rainfall amounts.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
The storm system will get further north by late Friday night,
especially after 9z, and this is when the rain will taper off
from southwest to northeast. A tongue of drier air will wrap in
quickly behind the departing low during the mid morning on
Friday. The winds will pick up more noticeably towards the late
morning, and especially during the afternoon. Downsloping flow
may allow temperatures to hover around 50 momentarily into the
early afternoon, but then the CAA will get going and
temperatures will trail off late in the day and into Friday
evening. An strong spoke of upper level energy will dive into
the departing storm system and give it another jolt. At this
point the storm will be too far north to impact the region in
terms of any meaningful precipitation, but the storm will
intensify rapidly in the Gulf of Maine late on Friday and this
will lead to increasing winds due to an increasing pressure
gradient developing over the region.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
An anomalous upper low with 500 mb height anomalies 2 to 3 standard
deviations below normal moves across the northeast Friday night. The
upper low will lift towards the Canadian Maritimes on Saturday. The
main surface low pressure, around 980 mb, is progged to be near
Maine Friday night. The surface gets captured by the deep upper low
Saturday morning as the system slowly moves the Canadian Maritimes.
As the upper low moves across the region Friday night, a few showers
cannot be ruled out. Temperature profiles north and west of the city
support the possibility of a few snow showers. The other story will
be strengthening NW winds Friday night into Saturday as the pressure
gradient tightens between the departing low and building high
pressure to the west. Expect sustained winds 15 to 25 mph with gusts
30 to 40 mph late Friday night. Sustained winds may increase a bit
Saturday morning to 20-30 mph and gusts could reach 40-45 mph,
especially at the coast. Thinking the winds should stay under
advisory levels at most locations. Forecast winds in the mixed
layer per NAM and GFS BUFKIT profiles are strongest Saturday
morning, with weakening winds in the afternoon. This should
translate to weaker sustained winds and gusts 30-35 mph in the
afternoon.

The pressure gradient continues to weaken Saturday night into Sunday
as surface high builds to our south and west. Upper ridging attempts
to build across the Ohio Valley, but the height field gets suppressed
from another upper low diving south out of southeast Canada. This
upper low ultimately stays well to our north and east, but will send
a shortwave and its attendant cold front towards the region on
Monday. Models have come into somewhat better agreement on a wave of
low pressure developing on the front Monday evening as it moves off
the New England coast.  The front brings with it a chance of showers
Monday afternoon and evening. There is also support aloft from a
strong upper jet across northern New England. Have increased PoPs to
high chance for now.

The front moves offshore Monday night with the upper trough axis
following on Tuesday. There is good agreement for sprawling high
pressure to settle over the eastern States for the middle week with
ridging building aloft.

Temperatures will be below normal in the 40s on Saturday, but then
will moderate into the 50s on Sunday and Monday. Temperatures drop
back below normal Tuesday into Wednesday.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Low pressure approaches from the south today and passes overhead
late tonight.

Easterly winds increase thru this afternoon. Speeds increase to
14-20 kt late today and this evening with gusts 20-25 kt. These
easterly winds back around to the NE/N overnight. Low level
wind shear is expected this evening for most coastal terminals
as a 40 to 50 kt jet moves into the area at 1-2 kft.

Ceilings could bounce between 2-3 kft to 3-4 kft today.
However, eastern terminals KISP and especially KGON could remain
rain free and VFR through most of the afternoon.

Rain becomes steadier thru the day, slowly expanding east late
this aftn and eve. MVFR ceilings lower to IFR late in the day
or this evening. These lowering conditions persist tonight, with
LIFR possible in spots.

     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 are likely for cigs and vis.

The afternoon KJFK haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KLGA TAF Comments: Amendments are likely for cigs and vis.

The afternoon KLGA haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KEWR TAF Comments: Amendments are likely for cigs and vis.

The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Amendments are likely for cigs and vis.

KHPN TAF Comments: Amendments are likely for cigs and vis.

KISP TAF Comments: Mainly VFR today with the bulk of the rain moving
in late this afternoon or evening. Patchy stratus lowering ceilings
at times is possible.

.OUTLOOK FOR 12Z THURSDAY THROUGH MONDAY...
.Friday...Becoming VFR. Chance of rain/snow showers inland and
rain showers near coast. W-NW G25-30kt.
.Saturday...VFR. NW G25-35kt
.Sunday...VFR.
.Monday...Mainly VFR, chance MVFR in rain showers late.

&&

.MARINE...
Winds and waves will then increase today in response to an
approaching area of low pressure, likely reaching SCA criteria on
the ocean waters this afternoon, and then on the other waters by
day`s end, therefore SCA will remain up accordingly. There may
be an extended period on the non-ocean waters late Thursday
night into Friday morning where winds aren`t meeting advisory
criteria as the low pressure center passes through the waters.
The winds are then expected to ramp back up at some point on the
back side of the storm, therefore have kept the SCA going
through the day on Friday for the ocean. For the ocean, seas
should remain elevated late Thursday night, so should still meet
advisory criteria right through Friday.

Winds increase Friday night into Saturday as the pressure gradient
steepens between the departing low to the north and high pressure
building to the west. Winds increase to gales Friday night on all
waters and will continue into Saturday afternoon. Have issued a gale
watch for this time period. Winds gradually weaken Saturday night to
small craft levels and then to 20 kt or less on Sunday. Sub-small
craft winds continue Sunday night into Monday before potentially
increasing a bit Monday night behind a cold front. Ocean seas will
remain elevated well above 5 ft through Saturday night. There may
even be 5 ft seas on the Long Island Sound late Friday night into
Saturday. Seas subside below 5 ft on Sunday and then gradually build
late Monday into Monday night.

&&

.HYDROLOGY...
An inch to an inch and a half of rain is expected Thursday into
early Friday morning across western sections, with a half inch
to an inch of rain expected across eastern sections. This could
result in some minor poor drainage flooding, more so over
northeast NJ and southern portions of Rockland County.

No hydrologic impacts anticipated Friday night through early next
week.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be rather high over the next couple of days
due to the full moon. Easterly winds today and tonight will pile
water along our western shores. Water levels may come close to minor
coastal flood benchmarks this morning along the vulnerable locations
in the western Long Island Back Bays. Issued a coastal flood
statement earlier for this mornings high tide.

More widespread minor flooding is expected with high tide cycle
tonight as easterly winds increase. This includes western Long
Island Sound, with localized moderate flooding possible at some
western Long Island Back Bay spots. Minor coastal flooding is also
likely across the lower NY Harbor.

A few locations may reach minor coastal flooding thresholds Friday
morning, but this will be localized if it occurs.

&&

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

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Friday for CTZ009-010.
NY...Coastal Flood Advisory from 11 PM this evening to 2 AM EDT
     Friday for NYZ071-073-078-177.
     Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for
     NYZ074-075-178-179.
NJ...Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for
     NJZ006-106-108.
MARINE...Gale Watch from Friday evening through Saturday afternoon for
     ANZ330-335-338-340-345-350-353-355.
     Small Craft Advisory from 5 PM this afternoon to 6 AM EDT
     Friday for ANZ330-335-338-340-345.
     Small Craft Advisory until 6 PM EDT Friday for ANZ350-353-355.

&&

$$
SYNOPSIS...JE/DS
NEAR TERM...JE/DS
SHORT TERM...JE
LONG TERM...DS
AVIATION...12/PW
MARINE...JE/DS
HYDROLOGY...JE/DS
TIDES/COASTAL FLOODING...
EQUIPMENT...

NWS OKX Office Area Forecast Discussion