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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KOKX 220011
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
811 PM EDT Sun Apr 21 2019

.SYNOPSIS...
Low pressure gradually develops off the Middle Atlantic coast
tonight. The low then tracks north towards Cape Cod on Monday into
Monday night. Weak high pressure briefly builds south of the area on
Tuesday. A cold front will move through early on Wednesday. A
warm front and its associated low pressure will move into the
region Friday, followed by a cold front Friday night into early
Saturday. High pressure builds in during next weekend.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
For this update have added some patchy fog to the coast, and
some interior places in CT especially as there will be a window
of areas of clearing, and with still a somewhat moist ground
and lightening winds progged during tonight felt that at least
patchy fog wording needed to be added. The question will be of
course the extent of cloud cover, and high clouds through this
evening especially. Perhaps this will play a role in limiting
fog. The NAM guidance is hinting at some low stratus as well.
Overall decided to decrease cloud cover for the first half of
tonight for much of the area, then the clouds increase a bit
late tonight. This lead me to lean more towards areas of patchy
fog through at least 8z or so. Used a NBM and GLAMP blend for
the most part with winds, temps, and dews for this evening as it
appeared to match obs well.

Broad upper low extending from the Appalachians down to the
Carolinas this evening will consolidate along the North Carolina and
Virginia coast by Monday morning. Weak surface low to our west will
also shift towards the south and off the coast tonight closer to the
reorganization of the upper low.

Any lingering showers will diminish this evening with the
expectation of a dry night. Dew points are progged to fall into the
40s tonight as some drier low level air works across the region.
Cloud cover is a bit tricky tonight as there could be lingering
stratocumulus and some high clouds. Have gone with a mostly cloudy
night. If the stratocumulus is less extensive, then cloud cover
may need to be lowered.

Lows will generally be in the 40s with some lower 50s in the NYC
metro.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
The main focus on Monday will be low pressure associated with the
aforementioned upper low. The upper low should pivot to a location
just southeast of Long Island by afternoon with a surface low
tracking near the 40/70 benchmark. Confidence in the forecast is
still not too high given the time frame and this is because there
remains a good amount of spread on how far north and west rain bands
from the low will reach in the afternoon. Some of the guidance is
still differing in the whether or not the surface low remains broad
or consolidated. Despite the lower forecast confidence, the highest
likelihood for showers in the afternoon and evening lies across Long
Island and southern Connecticut. Any showers should hold off until
late morning and then spread north in the afternoon.

Some high resolution guidance is also hinting at a broken band of
showers developing across the higher terrain to our north and
shifting south around the low in the evening. Will continue to
carry chance PoPs for the rest of the area to account for this
potential. Any instability present in the forecast soundings lies
below the freezing level, so do not anticipate lightning generation
and have left thunder out of the forecast.

High temperatures in the 60s are forecast for most locations with
readings near 70 possible in the NYC metro. Temperatures are coolest
across eastern Long Island and southeast Connecticut where the
higher chances of rain exist.

The upper low and surface low will gradually shift south and east of
Cape Cod Monday night. Showers may continue for the first half of
the night across eastern Long Island and southeast Connecticut. Some
drier air should work its way in as the system moves away for the
second half of the night with some clearing expected. Lows will be
in the upper 40s and lower 50s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
By Tuesday morning the upper level system that has been plaguing the
region will lift to the northeast with ridging building in, albeit
briefly. Tuesday should feature a good deal of sunshine with
temperatures getting above normal. Inland locations further west
should get well into the 70s, with an afternoon sea breeze cooling
down eastern and coastal sections. A good temperature spread should
develop during Tuesday afternoon with thermal differential due to
sea breeze development.

The next shortwave and frontal boundary then approaches for Tuesday
night into early Wednesday. Overall system is not overly impressive.
There may be a rumble or two of thunder across western sections
Tuesday night with the leading edge of showers as SPC has western
sections in a general t-storm risk. Not overly impressed with the
instability indices, therefore went with slight t-storm chance in
far western area Tuesday night, otherwise a light QPF event looks to
take shape with amounts probably around a tenth of an inch of so.
PWs only around an inch or so based on NAEFS ensemble guidance. The
front gets east of the region and washes out a bit by Wednesday
afternoon and drier air gets ushered into the region. Decided to
keep some POPs in through Wednesday morning as there is not complete
deterministic model agreement on the exact timing in which the front
completely clears the region.

Dry weather then follows as weak high pressure builds in for
Wednesday night into Thursday. Clouds should then increase quickly
by late in the day Thursday into Thursday night as a warm front and
its associated low pressure off to the west and southwest draws
closer. This system may have a bit more to work with with
respect some lower latitude moisture. This system has the
potential to bring a half inch to an inch of rain for late
Thursday night into Friday. The global models are then in
excellent agreement with respect to the timing of the system
exiting to the east Friday night. This should allow high
pressure to build in to begin next weekend, with high pressure
in control through the entire weekend.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Weak low pressure moves across tonight and then southeast of
Long Island on Monday.

Mainly VFR conditions are expected during the TAF period.
However, there will be potential for IFR stratus and fog late
tonight into Monday morning, especially for eastern coastal
terminals. The fog may become a higher possibility for those
locations that have initially less clouds such as KHPN, KBDR,
and KISP. KGON despite initially higher clouds has more low
level moisture so fog will be a possibility there as well.
Otherwise, more showers are forecast to develop Monday afternoon
with a chance for MVFR.

The winds will become light and variable near 5kt or less
tonight before becoming more northerly on Monday and increasing
to around 10 kt in the afternoon with some possible gusts up to
20 kt.

.OUTLOOK FOR 18Z MONDAY THROUGH THURSDAY...
.Monday night...Possible MVFR in showers early, then VFR.
.Tuesday...Mainly VFR. Chance of showers and MVFR at night.
Isolated thunderstorms near KSWF Tuesday night.
.Wednesday...Morning showers/possible MVFR, then becoming VFR.
.Thursday...VFR.

&&

.MARINE...
Rough seas will continue on the ocean waters through Monday night
due to a south to southeasterly swell. Have extended the SCA for
hazardous seas through this time period. Winds on all waters will
stay below SCA levels through Monday night as there will be a
relatively weak pressure gradient. Low pressure does pass nearby
Monday evening, but winds do not look to get above 20 kt.

Rough seas will continue on the ocean waters through Tuesday morning
due to a southeasterly swell. Seas on the ocean will range from 4 to
6 ft. Seas on the ocean will come down slightly Tuesday afternoon
and Tuesday night, with marginal SCA conditions expected into
Wednesday with seas generally at 4 to 5 ft. Seas will subside more
on the ocean Wednesday night into Thursday as high pressure builds
over the coastal waters with sub SCA conditions continuing on the
ocean through Friday with seas around 3 ft. Sub SCA conditions will
take place across all non-ocean waters through the period.

&&

.HYDROLOGY...
No hydrologic impacts are expected through Tuesday afternoon.

Any precipitation will be light Tuesday night into early Wednesday,
followed by precipitation on the order of a half inch to an inch
Thursday night into Friday with no hydrologic impacts expected
at this time.

&&

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

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Tuesday
     for ANZ350-353-355.

&&

$$
SYNOPSIS...JE/DS
NEAR TERM...JE/DS
SHORT TERM...DS
LONG TERM...JE
AVIATION...JM
MARINE...JE/DS
HYDROLOGY...JE/DS
EQUIPMENT...