Marine Weather and Tide Forecast for Greenport, NY

KEY MESSAGES
1) A strong frontal system brings showers late tonight into Friday morning and a second round of showers/isolated thunderstorms primarily during Friday evening. Strong to severe thunderstorms are possible with a squall line that is forecast to move through.

2) The coolest air mass of the season so far moves in this weekend along with Gusty NW winds Friday night into Saturday.

DISCUSSION

KEY MESSAGE 1

Showers and thunderstorm move through late tonight into early Friday morning in association with an approaching warm front. Thereafter, the region will be warm sectored with an approaching cold front to the west, deepening low pressure over northern New England/southeastern Canada, and a positively tilted upper level trough approaching from the west. After the passage of the warm front and ahead of the approaching cold front, winds shift to the SW and increase somewhat during the afternoon, bringing a surge of low level moisture, with dew points rising well into the 60s. Low level convergence along the cold front will allow for the development of low topped showers and thunderstorms that approach the western portion of the forecast area as a well defined squall line (as per most meso scale models) by late afternoon and early evening hours (anywhere from 5 pm to 7 pm, give or take an hour). With ample moisture in place, increasing low level convergence, and MLCAPE in the 500 to 1000 J/kg range, strong to potentially severe thunderstorms are possible, mainly for western portions of the area (NE NJ and Lower Hudson Valley). As the line approaches the coast, weakening is expected. However, even in these locations an isolated strong to severe thunderstorm cannot be ruled out. The Storm Prediction Center has placed much of the forecast area in a slight risk for severe thunderstorms.

The cold front and weakening squall line should push offshore between 9 pm and 11 pm, but post frontal rain looks to develop thereafter, keeping the chance for showers in the forecast for Long Island and southern CT through most of Friday night, with lesser chances as you head N and W.


KEY MESSAGE 2

The coolest air mass of the season so far moves in this weekend along with Gusty NW winds later Friday night into Saturday.

As mixing increases in the column immediately behind the cold front look for strong, gusty winds behind the front which may last right through a good portion of the afternoon. Also, behind the front the coolest weather of the fall is likely for the first half of the weekend. Daytime highs Saturday will be in the lower and middle 50s with a gusty NNW wind. Widespread 30s and lower 40s are expected for lows Saturday night. Some temperature moderation is likely towards late in the day on Sunday with daytime temperatures recovering a little into the upper half of the 50s with much lighter winds.

AVIATION /20Z THURSDAY THROUGH TUESDAY/
High pressure retreats to the east tonight, while a frontal system approaches from the west. The associated warm front will pass through Friday morning into early afternoon, followed by a cold frontal passage during the late afternoon into early evening hours.

VFR until late tonight, then showers will overspread the area from west to east after 06Z with ceilings lowering from MVFR to IFR. Following the warm frontal passage, expect gradual improvement with VFR conditions developing for the NYC and Lower Hudson Valley terminals around 18Z. Eastern terminals should follow a short time later, except for KGON which could take much of the day.

NE winds 5-10 kt will shift to the SE this afternoon into this evening. Speeds increase late tonight to around 10 kt at some coastal sites. Winds will then veer to the SW as the warm front passes with the potential for gusts to around 20kt.

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

Timing of lowering flight categories overnight into Friday morning could vary by 1-2 hours. Same with the improvement late morning into the afternoon.

A few strong to severe thunderstorms are possible after 21Z Friday with the approach of a cold front.

Chance of MVFR in showers overnight Friday (following the cold frontal passage).

OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY

Friday Afternoon: Improvement to VFR for the eastern terminals should occur by 21Z, but could take until around or shortly after 00Z Sat for KGON. SW winds G20-25kt in the afternoon. A fine line of showers/embedded thunderstorms approaches from the NW in the later afternoon into early evening hours. A few G40-50kt possible with the line.

Friday night: Showers and possibly a thunderstorm in the evening, with mainly MVFR conditions, then VFR. Cold frontal passage followed by W-NW winds G25kt.

Guidance is also trending toward a round of post-frontal showers Friday night into Saturday morning. Chance of MVFR with these showers.

Saturday: Mainly VFR. NW winds G25-30kt, diminishing in the evening.

Sunday-Tuesday: VFR.

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

MARINE
The pressure gradient decreases overnight with sub advisory conditions prevailing. However, conditions ramp up during Friday morning with small craft conditions quickly developing in a southerly flow, especially for the afternoon when the winds turn more SW ahead of an approaching cold front. The cold front passes through across the waters late Friday night with the winds becoming W, then NW during Saturday morning. Gales over the ocean waters are looking less likely for Friday into Friday night, and have converted Gale Watches to Small Craft Advisories for this period. Gale Watches remain in effect Saturday as there remains some uncertainty with the winds during this time frame, but continues to look less likely at this time.

For the non-ocean waters, SCA conditions across the eastern and central sound, Peconic and Gardiner's Bays, while the western sound and harbor look to not reach SCA.

By Friday night, SCA conditions expected all non-ocean waters lasting through the day Saturday and possibly into the first half of Saturday night, before subsiding to below SCA conditions.

Small craft conditions will likely linger for much of Saturday night on the ocean waters before sub advisory conditions return during Sunday morning. With high pressure building across the waters Sunday and settling nearby into early next week sub advisory conditions are expected to prevail.

OKX WATCHES/WARNINGS/ADVISORIES
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 11 AM to 6 PM EDT Friday for ANZ331.
Small Craft Advisory from 8 AM to 6 PM EDT Friday for ANZ332- 340-345.
Small Craft Advisory from 8 AM Friday to 6 AM EDT Saturday for ANZ350-353.
Gale Watch from Saturday morning through Saturday afternoon for ANZ350-353-355-380-383-385.
Small Craft Advisory from 11 AM Friday to 6 AM EDT Saturday for ANZ355.