Marine Weather and Tide Forecast for Groton, CT

NEAR TERM /THROUGH SATURDAY/
A confluent flow between the northern and southern branches of the polar jet will be featured across the Northeast. This will allow high pressure to build across eastern Canada and into the Northeast. To the south across the northern Mid Atlantic states, a frontal wave will move offshore late tonight into Saturday, passing south of the area. The latter of which will bring showers areawide tonight and a possible thunderstorm,but mainly after midnight into Saturday morning. There will be some elevated instability, but mainly across the southern half of the forecast area. With PW values approaching 2 inches, any embedded convection could produce brief heavy rainfall. Otherwise, the system is rather disjointed and will transition to some light rain by Saturday afternoon. High pressure and drying conditions will work in from the north as high pressure builds behind the departing low.

Expected rainfall amounts late tonight into Saturday will be between 0.25 and 0.50 inches. Stayed close to an NBM/WPC consenus. Right now, not buying into some of the higher amounts shown by the 12Z Canadian and ECMWF. 13Z NBM 50th percentile is 0.3 to 0.4", with the mean a bit higher (skewed toward higher amounts). However, probability of greater than 0.75" is only 15-25%.

Overnight lows will be in the upper 50s to lowers 60s, which is nearly normal. However. due to the cloud cover, northeast flow, and rain, highs on Saturday will likely not climb out of the 60s. This is more than 10 degrees below normal.

SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/
High pressure noses in from the northeast Saturday night into Sunday with only a slight chance of light rain during this time.
Model time height cross sections during this time show dry mid levels with moisture confined to the low levels, mainly below 700mb. In fact, while the forecast remains mostly cloudy during this time, it could very well remain dry through Father's Day and temperatures may be on the upper end of the guidance.

For the time, expect lows in 50s Saturday night and highs in the 60s for Sunday. This is on the cool side.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
A relatively zonal upper flow is anticipated through Wednesday night before it amplifies with a trough axis approaching Thursday night and passing through on Friday. This leads to weak surface high pressure over the region with a stalled boundary to our south. This boundary then becomes a warm front and advances north by Thursday with weak ridging aloft. A cold front then follows during Thursday night or possibly on Friday.

Highest chance of rainfall within the long term appears to be with the cold front passage, but there's uncertainty surrounding how probable it will be due to timing differences for the passage among the global models. A passage during the daytime Friday would probably bring a higher threat overall with a greater chance of heavy downpours as instability would be higher during the daytime.
12z LREF leans toward the faster side of the guidance envelope with the h5 trough axis and attendant cold front. The cold front is therefore more likely to pass through during Thursday night, mitigating the potential for severe weather and flooding impacts.
With that said, trends need to be watched so see if the frontal passage becomes more likely during the daytime on Thursday, or at the least, a prefrontal trough acting as a focus for convection.

NBM was used for temperatures through the long term period.
Thursday's high temperatures however may eventually need to be raised by at least 5 degrees given the progged h8 temperatures, but with the aforementioned convective uncertainty, have not adjusted from the NBM at this time. Heat impacts may factor in for some locations if it ends up being hotter than currently forecast, particularly away from the coast.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
A cold front will remain stalled south of the region as an area of low pressure develops and approaches along the front. The low exits towards the tail end of the TAF period.

VFR conditions expected through this evening and a portion of the overnight. MVFR is expected to hold off for the first half of the night, with higher chances late in the overnight mainly towards and after 08-09z and carrying into Saturday morning. Chances for showers increase late tonight, becoming likely early Saturday morning. The chances for IFR increase into Saturday morning, except for northern most terminals where MVFR is expected to prevail. SHowers are expected to become much more widely scattered by 20Z so there may be some improvements back up to MVFR briefly into the late afternoon with IFR becoming possible again after 00Z Sunday.

E to SE winds this evening around 10 kts, followed by the winds going more easterly tonight. The winds then become more northeasterly Saturday. The winds decrease to near 5 to 8 kts tonight into early Saturday but will be variable in direction for some terminals outside of NYC. The winds increase closer to 10 kt at most terminals during by midday.

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

Amendments may be needed later tonight into Saturday morning for changing flight categories.

OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY

Saturday night: Lowering chances of showers. MVFR to IFR possible.

Sunday: Chance of showers. Slight chance of a thunderstorm afternoon into early evening. MVFR to IFR possible at times. Otherwise VFR.

Monday: Chance of showers. MVFR to IFR possible at times. Otherwise VFR.

Tuesday: Mainly VFR.

Wednesday: Mostly VFR, with the chance of a period of sub-VFR.

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

MARINE
Sub advisory conditions are anticipated for all waters through the first half of the weekend. Ocean seas generally hold at 2 to 4 ft with a relaxed pressure gradient and a light onshore flow.
Marginal SCA seas are possible for the central and eastern ocean zones late Saturday night into Sunday morning.

Sub-advisory conditions should otherwise continue through Wednesday.

HYDROLOGY
No hydrologic impacts expected through early next week.

Next chance for impacts would be Thursday into Thursday night with any thunderstorms that manage to develop in a moist airmass in place. There's high uncertainty this far out in time regarding the probability, timing and magnitude of any impacts with this.

TIDES/COASTAL FLOODING
The rip current risk is low for the rest of today with a light easterly flow and limited swell. There is a moderate rip current risk on Saturday with an east to southeast swell.

OKX WATCHES/WARNINGS/ADVISORIES
CT...None.
NY...None.
NJ...Air Quality Alert until 11 PM EDT this evening for NJZ002-004- 006-103>108.
MARINE...None.