Groton, Connecticut 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

559
FXUS61 KOKX 191454
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1054 AM EDT Sat Jul 19 2025

.SYNOPSIS...
High pressure shifts offshore this morning. A warm front then
looks to pass through sometime late tonight into Sunday morning.
A cold front will follow Sunday evening. High pressure then
dominates through Wednesday. A cold front slowly approaches late
Thursday through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure centered just north of the area will move
offshore by late morning/early afternoon. A frontal boundary
currently draped over the Delmarva then starts to gradually
return north as a warm front. Aloft, a mostly zonal flow
transitions to some lowering heights ahead of a shortwave.

After a calm and cool morning, temperatures looks to rise into
the low to mid 80s. With high pressure shifting offshore, a
return flow sets up and brings a steady increase in moisture to
the area ahead of the warm front.

With the increasing moisture and lift ahead of the approaching
shortwave some showers are possible starting this afternoon.
Confidence is not too high in this and lowered PoPs from the NBM for
the afternoon, especially given proximity of the high.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The aforementioned warm front looks to move through sometime
tonight into early Sunday morning. Confidence in showers and
thunderstorms increases during this period, especially for the
eastern half of the area. Given the potential for pwats around
2 inches, any activity should be able to produce heavy
downpours. See Hydrology section below. It is worth noting that
in latest guidance there is some hints that the warm front does
not push all the way through the area and may skirt by the
southern half briefly before pushing east/northeast. This could
have potential impacts on moisture and convective activity.

There may then be a dry period the rest of Sunday morning into
Sunday afternoon. Before the severe thunderstorm threat, hot
and humid conditions are expected with highs now forecast to be
in the upper 80s to lower 90s and dewpoints in the lower 70s.
The NBM temperatures have trended up a bit and this combination
is giving more widespread 95 to 99 heat index values and a
couple areas right around 100. Given this is only one day of
these conditions, no Heat Advisory is expected at this time,
however, if temperatures and humidity trend up again, an
Advisory can not be completely ruled out if the one day
criteria of widespread 100 heat index is reached.

Attention then turns to potential severe thunderstorm activity
with an approaching cold front. Ahead of the front, the area
looks to be able to destabilize to 1500-2000 J/kg of MLCAPE. The
cold front appears decently strong for this time of year with a
sharp moisture gradient. 0-6km bulk shear will also be about 30
to 35 kts. This combination could result in scattered severe
thunderstorms Sunday evening. The SPC has introduced a slight
risk for our area. The main concern is wind, given no
significant directional shear through the layer. Large hail can
also not be completely ruled out, especially in any discrete
cells that form before an eventual potential cluster/broken
line forms. Forecast storm motion looks somewhat perpendicular
to the front which may allow the earlier activity to be more
discrete, so the hail threat favors more north and west of NYC.

High pressure builds in behind the cold front Sunday night and
leads to quiet conditions through Monday night.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
***KEY POINT***

* Heat and humidity return for the end of next week.

An extended period of quiet weather is expected during the long
term forecast as an upper ridge building into Thursday, and
then weakening as another shortwave trough moves into eastern
Canada and the northeast late Thursday into Friday. At the
surface high pressure dominates into Thursday. A weak surface
trough develops inland Wednesday afternoon with a slight chance
of precipitation. A stronger surface trough develops for late
Thursday into Thursday night with high pressure weakening and
shifting south and east. And there will be higher, and more
widespread, chances for precipitation. Temperatures will be near
seasonal normals through Tuesday night, then the heat will
build with temperatures above normal Wednesday into the end of
the week. Humidity levels will also be increasing beginning
Wednesday as a return flow setup up later Wednesday with high
pressure moving east of the area. For Thursday and Friday with
the combination of heat, with highs in the upper 80s to mid 90s,
and humidity, with dew points in the lower 70s, there is the
potential for a heat advisory for Thursday and Friday with a 2
day period of heat indices reaching 95 to 103 across much of the
area.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
High pressure moves offshore this afternoon, giving way to a
warm front approaching from the south this evening. The warm
front is forecast to pass over Long Island through late tonight
into Sunday morning. A cold front approaches Sun afternoon,
crossing Sun evening.

VFR through evening push, although a brief shower is possible
this afternoon. Increasing likelihood of MVFR cigs for most
terminals overnight (aft 03z). Scattered showers and
isolated thunderstorms overnight into Sun am push, highest
confidence is for the coastal terminals east of NYC/Nj metro.

Light N/NE or variable winds become southerly at 5-10kt this
afternoon into evening, then light SW or variable late tonight
into Sun AM push.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Spotty showers possible for Sat aft/eve push. Low and sparse
coverage of tsra after 03z through Sun AM push. MVFR conds
likely after 03z thru Sun AM push.

Timing of MVFR and TSRA may be off by 1-2 hours and need to
refined.

S winds to 15 kt likely for KJFK, possible for KLGA, btwn 20z
and 24z with coastal jet this afternoon.

.OUTLOOK FOR 12Z SUNDAY THROUGH WEDNESDAY...

Sunday: MVFR AM, improving to VFR late morning. MVFR or lower
conds and W/NW winds gust in excess of 30kt in any
showers/thunderstorms along and ahead of an approaching cold
during the late afternoon/early evening hours. SW winds 10g15kt
Sun aft/evening.

Sunday night through Wednesday: VFR.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90

&&

.MARINE...
Winds and waves look to stay below Small Craft Advisory criteria
through next week with a weak pressure gradient in place.
However, there is potential for severe thunderstorms Sunday
evening. Locally stronger wind gusts and higher waves are
possible in any thunderstorm.

&&

.HYDROLOGY...
Widespread hydrologic impacts are not anticipated through this
weekend. However, with potential precipitable waters values
around 2 inches, any thunderstorms could produce brief/locally
heavy rain rainfall. Higher overall chances of thunderstorms
would be Sunday afternoon, but storms would be moving quickly
enough to mitigate a flash flooding threat.

There are no hydrologic impacts expected from Sunday night through
next week with dry weather much of the time.

&&

.TIDES/COASTAL FLOODING...
The rip current risk for Saturday and Sunday is low at all the
ocean beaches with 2-ft southerly wind waves at 4 to 6-sec
period and S winds mostly 10 kt or less.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

SYNOPSIS...MET/JT
NEAR TERM...JT
SHORT TERM...JT
LONG TERM...MET
AVIATION...NV
MARINE...NV
HYDROLOGY...MET/JT
TIDES/COASTAL FLOODING...