Marine Weather and Tide Forecast for Darien, CT

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
Isolated showers have developed north and west of NYC and will continue early this evening before eventually diminishing with the decrease of diurnal instability. Increased clouds tonight per visible satellite trends. Forecast temperatures and dewpoints on track with just slight adjustments to better match observed trends.

SW flow tonight will advect moisture back into the area. There is still quite bit of uncertainty with the possible development of a convective MCS that rides over the northern portion of the developing ridge. Some CAMs indicate that this MCS may quickly traverse through parts of the area sometime late tonight into Sunday morning. At this time have opted not to forecast anything more than a slight chance as the potential MCS continues to show rapid weakening as it approaches the area. Best chance to see any sort of precipitation would be for areas north, but once again, confidence in the occurrence of this is much lower than normal at this time frame.

Lows tonight will be in the 70s with dewpoints in the 60s.

SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/
* Extreme Heat Warning for much of the region from Sunday afternoon through 8 PM Tuesday including NYC.

* Heat Advisory is now in effect for Sunday and an Extreme Heat Watch on Monday and Tuesday remains, for portions of Long Island and coastal Middlesex and New London Counties.

Sunday morning, the development of the ridge will be well underway with heights continuing to rise aloft and high pressure strengthening to the south. There is the potential of some morning cloud cover or showers from a decaying MCS mostly across our northern zones, but otherwise skies will be mostly clear. Sunday is expected to be the beginning of what may very well be a record setting heatwave for some locations.

SW flow will continue to allow dew points to rise into the upper 60s and lower 70s with temperatures climbing into the 90s for much of the area. Some of the hottest spots near the NYC metro may approach 100 degrees. Heat index values will be generally 100-105 for much of the area. For areas closer to the coast, heat index values of 95-100 will be expected.

Lows at night will not offer much relief as low temperatures will only be in the 70s with more urban locations possibly not dropping below 80.

Given the expected excessive heat, the Extreme Heat Watch that was in effect for NYC has been upgraded to an Extreme Heat Warning for Sunday through Tuesday. The highest heat index values will occur each afternoon, but especially on Monday and Tuesday.

LONG TERM /MONDAY THROUGH SATURDAY/
* Extreme heat continues Monday and Tuesday for portions of the region

* Heat wave potentially breaks later in the week (Thursday through Saturday) with more unsettled weather pattern taking shape

Strong ridging with high pressure remains dominant feature early in the week with this ridging weakening mid to late week, allowing for more disturbances to move across along the periphery of this ridge.

Regarding extreme heat, the new forecast incorporates a blend of MOS, NBM and the previous forecast for the max temperature forecast and dewpoint forecast Monday. Used NBM for temperatures Tuesday and thereafter.

The max temperature forecast for Monday used 40 percent NBM, 40 percent previous forecast and 20 percent MOS consensus. MOS did shift several degrees lower compared to last run. Did not want to make significant changes just based on suite of model runs that being 12Z this morning. 12Z MOS model data did lower by several degrees compared to previous run and in some locations more. That is why MOS consensus was weighed less.

One significant trend Monday is that dewpoints rise. Synoptically, low pressure passes well to the east of the area and with high pressure to the south and west, a more southerly flow will be driven into the local region. If low pressure does trend any stronger or closer east of the area over the Atlantic, that would invoke a more southeast flow as opposed to the south flow which could trend temperatures downward with subsequent forecasts.

Models still indicate 850mb temperatures near 21 to 23 degrees C with strong ridging at 500mb, well above 590 dm for Monday.
Subsidence will allow for dry conditions and mostly sunny sky conditions. Surface temperatures will easily rise with diurnal heating as a result and the southerly flow will provide more humid conditions. Max apparent temperatures forecast 105 to 110 across portions of NYC, NE NJ, Lower Hudson Valley and portions of Southern CT for Monday. Extreme heat warning continues to cover this as well as areas that are close the 105 degree heat index mark.

Tuesday, 500mb shows a slight decrease in height, but still prominent ridge remains established across the region. 850mb temperatures Tuesday still near 22 to 23 degrees C. Daytime troughing appears more evident Tuesday, giving more of a westerly component. Pressure gradient is not too strong so winds near 5-10 kt SW to W. More daytime mixing expected but dewpoints still mid 60s to near 70 for the region. Max apparent temperature forecast just slightly less than the previous day.
Across the extreme heat warning area, most locations are around 105 degree heat index with some locations slightly higher.

Outside the extreme heat warning, we have an extreme heat watch for Nassau into Western Suffolk as well as Southeast CT along the coast.
105 degree heat index values are possible within this region but most forecast values are in the mid 90s to around 100 range.

Wednesday marks a transition time period where the heat wanes with more height decreases at 500mb with 850mb temperatures more within the 18 to 20 degree C range. Max apparent temperature range Wednesday forecast Western Suffolk west through NE NJ and Lower Hudson Valley and much of Southern CT, more in the 95 to 100 degree C range. This forecast is a few days away and there is uncertainty of a few degrees with temperature and dewpoints.
This could very well make the difference with heat indices as a result. Heat index could potentially get to 105 for much of the area as previous days. So, heat headlines may need to get extended into Wednesday.

Otherwise, less ridging and the approach of a cold front Wednesday which could very well stall out thereafter will present a more unsettled weather pattern. Multiple model guidance sets indicates a substantial cool down Thursday through Saturday, with temperatures on average for highs more in the 80s. Chances for showers and thunderstorm reappear in the forecast.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
VFR with high pressure in control.

SW-S 5-10 kt expected this afternoon. Along the coast, expect the afternoon sea breeze to produce winds closer to 10-15 kt.
Winds become light and variable tonight. Winds on Sunday will be from the SW. Can not rule out an isolated shower this afternoon/evening.

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

S-SE harbor breeze should hold just E of KEWR this afternoon, but may make it in there and at KTEB toward 00Z Sunday.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY

Sunday afternoon: VFR. Chance of an isolated shower or thunderstorm in the afternoon. WSW-SW winds G15-20kt in the afternoon.

Monday and Tuesday: VFR.

Wednesday: Chance of showers/tstms in the afternoon/evening mainly for KHPN/KSWF.

Thursday: Chance of showers/tstms mainly in the afternoon/evening.

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

MARINE
Below SCA conditions expected through Sunday night with some occasional 5 feet seas Sunday afternoon/evening. Sub-SCA conditions forecast Monday through Thursday night with the pressure gradient overall not being steep as large scale high pressure ridge is holding strong much of the time.

HYDROLOGY
There are no hydrologic concerns with mainly dry conditions prevailing through the middle of next week.

TIDES/COASTAL FLOODING
Low risk for rip currents for all ocean beaches with a diminished swell and lower offshore wave heights through early this evening.

With an increase in onshore swell (3 to 4 ft) and southerly winds (SW 10-15 kts), a moderate risk of rip currents is forecast for all ocean beaches on Sunday.

Winds lighten and become more variable Sunday night into early Monday with a resumption of light southerly flow Monday afternoon (5-10 kts). Onshore swell decreases for Monday (2 to 3 ft). There is a low risk of rip currents forecast for Monday for all ocean beaches.

CLIMATE
Increasing heat may result in record high temperatures Sunday through Tuesday.

Sunday's Record Highs (June 22): EWR 101 / 1988 BDR 93 / 1949 NYC 98 / 1988 LGA 99 / 1988 JFK 94 / 2012 ISP 94 / 2012

Monday's Record Highs (June 23): EWR 99 / 2024 BDR 91 / 2010 NYC 96 / 1888 LGA 95 / 2024 and previous years JFK 94 / 2010 ISP 91 / 1999

Tuesday's Record Highs (June 24): EWR 97 / 1966 BDR 94 / 1966 NYC 96 / 1888 LGA 96 / 2013 JFK 97 / 2010 ISP 96 / 1966

OKX WATCHES/WARNINGS/ADVISORIES
CT...Air Quality Alert from 11 AM Sunday to 11 PM EDT Monday for CTZ005>012.
Extreme Heat Warning from noon Sunday to 8 PM EDT Tuesday for CTZ005>010.
Heat Advisory from noon to 8 PM EDT Sunday for CTZ011-012.
Extreme Heat Watch from Monday afternoon through Tuesday evening for CTZ011-012.
NY...Extreme Heat Warning from noon Sunday to 8 PM EDT Tuesday for NYZ067>075-176-178.
Heat Advisory from noon to 8 PM EDT Sunday for NYZ078-080-177- 179.
Extreme Heat Watch from Monday afternoon through Tuesday evening for NYZ078-080-177-179.
Air Quality Alert from 11 AM to 11 PM EDT Sunday for NYZ078>081-177-179.
NJ...Extreme Heat Warning from noon Sunday to 8 PM EDT Tuesday for NJZ002-004-006-103>108.
Air Quality Alert from 11 AM to 11 PM EDT Monday for NJZ002- 004-006-103>108.
Air Quality Alert from 11 AM to 11 PM EDT Sunday for NJZ004- 006-103>108.
MARINE...None.