Area Forecast Discussion
Issued by NWS Upton, NY

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966
FXUS61 KOKX 250521
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
121 AM EDT Wed Apr 25 2018

.SYNOPSIS...
Low pressure over the Southeast states will move northeast
toward the area today, then pass over the area tonight, with a
trough of low pressure then crossing the area on Thursday. Weak
high pressure will briefly build in Thursday night, then give
way to another coastal low impacting the area Friday and Friday
night. A cold front will move through Saturday and Saturday
night, followed by high pressure building over the area from
Sunday through Tuesday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Minor changes were made with this update to reflect the latest
trends in observations and guidance. The forecast appears on
track.

Steady rains moving across western locations and will track
to the NE early this morning. The intensity should increase
from light to moderate as well from SW to NE over the area.

Low temps are a blend of GFS/NAM MOS and 2m raw temps, with
lower 50s in NYC metro and western Long Island, and mid/upper
40s elsewhere.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
Combo of a decent shot of Atlantic inflow and elevated
instability ahead of the approaching surface low will lead to
rain, heavy at times, along with chance of thunder as TT
increases to near 50 and Showalter indices decrease to near of
below 0C. This area should lift NE and off the eastern New
England Coast Wed night, leaving the area in a col for most of
the night with light rain and patchy fog developing. NWP
guidance shows some phasing of northern/southern branches of the
jet stream late Wed night, and as this takes place the southern
stream low and mid level shortwave trough should pass through
late Wed night, along with a cold frontal passage associated with
the northern branch of the jet stream and a surface low well to
our north. Elevated convection could be reinvigorated by this
cold front, and so have kept slight chance mention of thunder in
the forecast for Wed night.

Temps will be below seasonal norms but certainly not unusual for
a springtime rain event, with not much diurnal changes. Highs
Wed will be in the 50s, and lows Wed night in the upper 40s and
lower 50s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
During the Thursday through Saturday time frame, features to watch
include departing shortwave over the northeast, southern stream
shortwave traversing across the southeast states ahead of vigorous
northern stream shortwave that moves out of the upper midwest toward
the east coast by Saturday.

Any lingering rain should end early Thu morning with weak
ridging and dry weather returning through Thu night. Meanwhile,
the aforementioned southern stream shortwave will lift
northeast as the downstream trough amplifies, with deep SW flow
setting up. There are some differences aloft, the American
models track the shortwave further west than the EC/CMC/UKMET,
leading to higher rain amounts on Fri. Will need to fine tune
this in the coming days, but for now have increased CHC PoPs a
bit.

During the Saturday night through Monday timeframe, upper
trough pushes east, and there is the potential for additional
showers associated with a weak cold front late Saturday into
Saturday night, although probabilities do not appear to be high
at this time. Greater likelihood would be NW of the area as
trough closes off north of the Great Lakes region.

Upper trough lingers Sunday but gives way to building ridge as sfc
high builds by Monday.

Temperatures remain right around seasonal norms, with Sunday perhaps
a few degrees cooler behind the cold front. Temperatures warm early
next week.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Low pressure approaches from the southwest tonight into
Wednesday, and then moves overhead Wednesday Night.

MVFR conditions continuing to lower to IFR overnight, with
moderate to heavy rain for the morning push. Isolated tstms
possible Wed morning into early afternoon but confidence remains
low, so have kept out of the TAFs. Potential for LIFR or lower
conds in stratus/fog for evening push.

E winds increase to around 15 kt with gusts to 25 kt for coastal
terminals Wed morning. Winds subside in the early afternoon,
becoming light and variable for evening push.

LLWS possible with SE winds at 40-45 kt at 2 kft.

.OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY...
.Wednesday Night...LIFR or lower in stratus/fog possible for
evening push, gradual improvement to VFR late Wed night into
early Thu morning.
.Thursday...VFR.
.Friday-Saturday...VFR. A chance of showers with areas of MVFR
conditions.
.Sunday...VFR. W wind 10-15KT, G20-25KT.

&&

.MARINE...
Minor changes were made with this update to reflect the latest
trends in observations and guidance. The forecast appears on
track.

With the continuance of onshore flow, ocean seas continue to
build to 4-6 ft. Then as the pressure gradient tightens ahead
of the approaching sfc low, expect wind gusts gusts of 25-30 kt
mainly during the first half of the day. Seas on the ocean
waters should remain AOA 5 ft into Sat before subsiding from W
to E as the pressure gradient weakens.

&&

.HYDROLOGY...
A widespread 1.00-1.50" of rain is likely today. Heavy rain at
times could cause minor urban and poor drainage flooding,
especially if the higher end of the expected rainfall range is
realized. Expecting the bulk of the rain to fall this morning,
perhaps lingering into late afternoon across SE CT.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 AM this morning to noon EDT today
     for ANZ330-335-338-340-345.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ350-353-
     355.

&&

$$
SYNOPSIS...Goodman/24
NEAR TERM...Goodman/Maloit/PW
SHORT TERM...Goodman
LONG TERM...24
AVIATION...CB/NV
MARINE...Goodman/24/Maloit
HYDROLOGY...Goodman/24
EQUIPMENT...



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