Marine Weather and Tide Forecast for Shelter Island, NY

NEAR TERM /THROUGH TONIGHT/
Some adjustments made, primarily rainfall amounts through mid- afternoon based on observations and trends. The forecast is otherwise mainly on track.

As the coastal low develops this morning look for the steady rain to continue until about midday or so for the eastern half of the region. The primary low begins to fill in with an occluded front slowly pushing towards the area. The 700 mb lobe of low pressure forms over the eastern half of the area during the day so this should begin to shut off the Carlson conveyor belt of Atlantic moisture as warm advection decreases into the afternoon. Late in the day the 700 mb low consolidates and starts to get further north. This eventually completely shuts off the more organized wet weather, although mainly lighter showers will pivot through into tonight with the upper level portion of the system lingering. With the sfc reflection getting a bit further east and north the winds are expected to go to more of a northerly component and be more out of the northeast this afternoon, followed by more of a true northerly flow tonight. With the cloud cover and more of a NE flow regime look for temperatures to run well below average. Temperatures have been continued to be lowered from previous forecast cycles and are likely to not get out of the upper 40s inland to the NW, and the lower half of the 50s elsewhere across the region and closer to the coast. As the coastal low develops the winds should increase further, especially closer to the coast where gusts get to around 30 to 35 mph in some spots. Event rainfall totals should end up averaging 1 to 2 inches across the region, with the highest totals across the eastern third of the area in closer proximity to the strongest mid level warm advection and warm tongue from the LLJ. For more details with respect to the rain and any hydrologic response please refer to the hydrology section.

Cyclonic flow continues into tonight, however the best forcing gets north of the area and into New England with deepening of the coastal system, especially in the mid levels. By mid to late evening the winds should begin to decrease as the wind direction becomes more out of true north, then more NW late. Look for periods of light shower activity with any additional rainfall to be on the light side with the highest RH in the lowest 10kft as the system becomes vertically stacked. Mainly cloudy skies persist with temperatures averaging below average with lows mainly in the 40s region wide.

SHORT TERM /FRIDAY THROUGH SATURDAY/
The cool weather regime continues as the upper level low more or less temporarily stalls over Northern New England and Upstate NY Friday into Friday night. Cyclonic flow continues in the column with a good deal of cloud cover remaining. Somewhat drier air begins to work in down lower in the column on a W flow. This should get temperatures a bit warmer, but still running below average with a good deal of cloud cover with mainly upper 50s and lower 60s for max temperatures. Another spoke of mid and upper level energy pivots through into the afternoon and this looks to yield another round of at least some scattered shower activity. The activity is likely to linger into Friday night as well with the relatively higher chance of showers further N and NW. Minimum temperatures Friday night will mainly range from the middle 40s inland to the north, to around 50 or in the lower 50s for the metro and coast.

For Saturday the upper level low slowly pushes northeast into Maine and Nova Scotia. A deep WNW flow will reside in the column keeping the region primarily dry with only the slightest chance of a shower or a few sprinkles mainly across northern most sections as the cold pool aloft lingers with mainly broken cloud coverage. With the upper level low slowly lifting out and more of a land component to the wind temperatures may be able to get a few degrees warmer, but still average below normal as max temperatures should get into the lower and middle 60s. This would still be around 10 degrees below normal for this time of the year.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
**Key Points**

* Dry conditions for the area Sunday and Monday, with shower chances returning by late Monday and Tuesday.

* Slightly below normal temperates expected generally, with Memorial Day the warmest of the period; near normal.

Decent model agreement on a slow-moving, closed mid-level low east of the area over New England to start the period. The local area thus resides under a deep cyclonic/NW flow aloft, with a few weak shortwaves rounding the base of the closed low through Tuesday.
Ridging aloft then build over the area on Tuesday, while another deep low approaches from the Great Lakes region by midweek.

Have kept the forecast dry for Sunday with the cold pool aloft and fairly dry airmass, but can't rule out an afternoon shower especially with some shortwave energy passing over the area in the afternoon (model guidance consensus still hinting at this possibility) along with more favorable mid level lapse rates. This looks most likely for the interior, LoHud and Southern CT. At a minimum, an increase in cloud cover Sunday afternoon looks likely for the whole area, with below normal high temperatures in the mid to upper 60s.

By Monday the surface flow becomes more westerly/southwesterly, as high pressure/upper ridging builds in. With some waa, expect a warmer day than on Sunday, with mainly dry conditions for the much of the day. Clouds will be on the increase, however, by Monday afternoon/evening as surface low pressure originating over the southeast US heads northeast toward the region. This system will have some moisture to work with given its origin, with mean PWATS from the LREF (NAEFS/GEFS) of around 1" by early Wednesday. Usual model timing differences this far out, so have used the ensemble approach for PoPs and Wx, increasing the precip potential by Tuesday morning and keeping chances in through Wednesday. Given the increased cloud cover and shower activity, temperatures will remain slightly below normal in the mid and upper 60s.

AVIATION /15Z THURSDAY THROUGH MONDAY/
Low end MVFR and IFR cigs continue across the terminals this morning, along with period of rain, some of it moderate to locally heavy at times. Gusts have been slow to develop but are increasing east of NYC. Gusts will be from the ENE 15G20-25kts.
A return to high end MVFR may occur later this afternoon, with a lowering of cigs again early Friday and toward the end of the TAF period.

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

Amendments likely mainly for changes in flight categories.
Gusts may be more occasional than frequent.

OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY

Friday: Chance of showers with MVFR cond at times. N winds 10- 15G20kt E of the NYC metros Thu evening.

Saturday and Sunday: Mainly VFR. NW winds G15-18kt.

Monday: VFR.

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

MARINE
SCA for western waters and Gale Warning for eastern waters continues through this afternoon. Occasional gales possible on the waters where the advisory is currently up, but not enough for an upgrade to a warning. Gale warning may need to be extended by a few hours over the easternmost waters, otherwise winds eventually fall below advisory thresholds through the night tonight. Seas will remain elevated on the ocean with advisory conditions likely through at least Friday morning. Then hovering 4-5 feet into Saturday.

All waters look to be blw SCA lvls Sun and Mon. Seas may then build on the ocean to SCA lvls late Tue.

HYDROLOGY
Rainfall event totals are to average generally 1 to 2 inches, but with higher amounts of over 2 inches possible across eastern Long Island and southeastern CT. This is where more nuisance urban poor drainage related flooding is more likely, but overall flood concerns remain low with the rain expected to fall over a long enough duration. Thereafter there remain no significant hydrologic issues through the remainder of the forecast period.

TIDES/COASTAL FLOODING
A prolonged E-NE flow continues into this afternoon, backing N/NE toward evening. This backing of winds should help limit the magnitude of coastal flooding for most areas, but potentially enhance impacts along Peconic and Gardiners Bay and north shore of LI.

The latest forecaster adjusted Stevens (75th percentile weighting), ETSS, PETSS STOFS guidance blend signals widespread minor coastal flooding for the south shore of Nassau County, the twin forks of LI (localized moderate impacts possible for north facing areas along the bayfront), and along much of LI Sound.

Localized minor coastal flooding likely for NY/NJ harbor where winds will back to the N/NNE earlier. Magnitude of coastal flooding for central and eastern great South Bay, Moriches, and Shinnecock bays will depend on tidal piling trends, but looks to be localized here.

For Fri evening high tide, coastal flooding looks to be more localized for the Fri eve high tide cycle, to southern Nassau and SW CT, in response to offshore flow and subsiding onshore swells.

Potential for localized coastal flooding Sun into early next week with approach of new moon, causing areas to need as little as 1/4ft of tidal departure for minor coastal flooding.

As far as shoreline impacts, along the north shore of the south fork of Long Island, breaking waves of 1 to 3 ft may cause dune erosion and localized washovers, as well as enhance splashover and flooding onto shoreline roads and properties. Along the ocean front and Orient Point, breaking waves of 4 to 6 ft on an east to west sweep will result in beach erosion and beach flooding during the times of high tide. Localized dune erosion is possible. Along the north shore of Long Island, breaking waves of 3 to 4 ft will cause dune erosion, localized washovers, as well as enhance splashover and flooding onto shoreline roads and properties.

CLIMATE
Record minimum maximum (coldest high temperatures) are possible for today, May 22nd. Here are the records and forecast high temperatures for the date:

NYC: 54/1894, forecast high: 53 JFK: 55/1967, forecast high: 53 LGA: 57/2003, forecast high: 53 EWR: 56/2003, forecast high: 53 BDR: 54/2005, forecast high: 51 ISP: 54/2003, forecast high: 54

OKX WATCHES/WARNINGS/ADVISORIES
CT...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for CTZ009>012.
NY...Coastal Flood Advisory from 6 PM to 10 PM EDT this evening for NYZ071-073-078-176-177.
Coastal Flood Advisory from 2 PM this afternoon to 11 PM EDT this evening for NYZ079>081-179.
Coastal Flood Advisory from 2 PM this afternoon to 7 PM EDT this evening for NYZ178.
NJ...None.
MARINE...Gale Warning until 6 PM EDT this evening for ANZ331-332-340- 350-353.
Small Craft Advisory until midnight EDT tonight for ANZ335-345.
Small Craft Advisory until 6 PM EDT this evening for ANZ338.
Small Craft Advisory until 6 AM EDT Friday for ANZ355.