Old Greenwich, Connecticut Weather Forecast Discussion

987
FXUS61 KOKX 201749
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
149 PM EDT Sat Sep 20 2025
.SYNOPSIS...
High pressure over the area tonight will slide off the New
England coast on Sunday, but remain in control through Monday
night. A warm front lifts north into Tuesday, followed by a
cold front on Wednesday. High pressure then tries to build in
for the rest of the week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Early autumn surface high pressure will remain over New
England tonight. This will set the stage for a cool overnight
with good radiational cooling conditions, especially the first
half of the night. There is a weak mid and upper level shortwave
that approaches underneath the large ridge over the northeast
late tonight. This will likely bring increasing mid and high
clouds, especially towards day break. Not expecting this to
impact low temperatures too much since the air mass preceding
the clouds is dry and winds should diminish after sunset.
Adjusted NBM deterministic lows down a few degrees across the
interior. Otherwise, lows are forecast to fall into the into the
mid to upper 40s inland and low to mid 50s elsewhere. The NYC
metro will likely only fall into the upper 50s.
Patchy fog is possible late tonight and early Sunday, mainly for
the interior and river valleys.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Dry conditions will continue through Monday night.
Mid and high clouds associated with the aforementioned
shortwave Sunday morning should clear Sunday afternoon. The
surface high will shift off the New England coast as western
Atlantic ridging sets up well ahead of broad troughing over the
central states. Winds will become easterly on Sunday leading to
temperatures a few degrees below average with highs in the upper
60s and low 70s. Mostly clear skies along with surface ridging,
weak winds, and dry air should lead to another cool night. Lows
Sunday night look to fall into the mid/upper 40s inland and
lower to middle 50s closer to the coast. Patchy river valley fog
is once again possible early Monday morning.
Surface ridging will remain in place Monday and Monday night
despite the surface high off the New England coast. The air
mass will begin to moderate allowing temperatures to return to
normal levels in the lower to middle 70s. The surface ridging
begins to weaken Sunday night as upper level heights start
falling. A frontal system gradually slides eastward, but should
remain well to our west Monday night. The only change to
sensible weather will be increasing clouds, including potential
for some stratus near the coast late Monday Night/early Tuesday.
Temperatures will also be milder with lows in the mid 50s to
low 60s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
NBM was closely followed through the period.
Key Points:
* The highest probability of shower activity looks to take place
  late Tuesday, and once again late Wednesday and Wednesday night.
* Uncertainty increases late in the week. The various global
  guidance camps maintain differences in the progression of both the
  northern and southern branches of the jet stream. This results in
  differences in sensible wx, especially from Thursday night through
  Friday night.
Temperatures are expected to average near to slightly above normal
through the period. Temperature uncertainty through the period will
center largely around cloud cover during the daytime hours,
especially late in the period.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
High pressure continues to build in from the northwest today
before settling just to the north tonight into Sunday morning.
VFR.
ESE winds this afternoon gradually diminish, becoming light and
variable for some outlying terminals overnight. An E to ESE wind
Sunday morning will shift to the SE by late morning at around 10 kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
There remains uncertainty around the frequency of gusts through late
morning.
.OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY...
Sunday - Monday: VFR.
Monday night: VFR to start, with MVFR ceilings possible late.
Tuesday: MVFR possible with chance of showers in the afternoon and
evening. A thunderstorm is also possible.
Wednesday: MVFR possible with a chance of showers.
Thursday: Mainly VFR. MVFR or lower possible in isolated showers.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
Winds and seas have subsided below SCA levels on the ocean
west of Moriches Inlet this afternoon. Conditions are expected
to remain below SCA levels on all waters through Sunday night.
Long period SE swells will arrive on Monday, but seas should
remain below 5 ft through Monday night. A weak pressure gradient
on Monday and Monday night will lead to winds well below 25 kt.
SE swells could lead to a period of more widespread 5 ft seas on
the ocean by early Tuesday, and possibly prevailing at 4-5 ft
for Wednesday and Thursday.
&&
.HYDROLOGY...
There are no hydrologic concerns through late next week.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk of rip currents along local Atlantic
facing beaches through Sunday with 3 to 4 ft swells from the
east at 6 sec and a 10 to 15 kt NE/E flow. The risk likely
increases to high on Monday with longer period 4-5 ft swells.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...99
AVIATION...JP
MARINE...DS
HYDROLOGY...DS
TIDES/COASTAL FLOODING...

NWS OKX Office Area Forecast Discussion