Marine Weather and Tide Forecast for Port Jefferson, NY

KEY MESSAGES
1) A strong frontal system brings periods of rain and the potential for thunderstorms to the region on Monday. This could lead to flooding in urban and poor drainage areas. Wind gusts 40 to 50 mph are also expected, with locally higher gusts.

2) Localized minor coastal flooding and beach erosion possible Monday into Monday night.

3) A drier and colder airmass settles into the area midweek.

DISCUSSION

KEY MESSAGE 1
An unsettled wet and windy start to the workweek.

Amplifying trough sharpens over the Midwest on Monday, with a deepening surface low driving through the Great Lakes sending attendant fronts through the region locally.

Warm front lifts through early Monday morning, with flow turning southerly and increasing as low level jet develops overhead.
Showers accompany the fropa and WAA, and can't rule out a few embedded rumbles of thunder with the activity as Showalter values fall just below 0. After this initial wave,, breaks in steady rain likely develop, with more intermittent showers possible into the afternoon. With the warm air advection and rise in dew points, continued to carry fog for coastal areas much of the day.

Winds will continue to increase and become more gusty, especially Monday afternoon. Soundings prog an 80 to 90 kt LLJ developing at 925 mb. Helping to mitigate the core of these winds from mixing down however is a stout inversion just above the surface.
Even half of this though yields gusts above 40 kt, so hoisted Wind Advisory for coastal areas and S CT from 2pm Mon thru 5am Tue. S or SE winds sustained 15 to 25 mph, with gusts 45 to 50 mph, highest along the coast. Localized gusts along the immediate coast could approach or exceed 60 mph, though likely isolated if it were to occur.

Intermittent showers persist in the afternoon before a decaying squall line approaches from the west ahead of the advancing cold front. Hi res CAMs indicate the line gets into western portions of the area, including the NYC metro, in the evening after 6pm. Limited elevated instability with strong ll shear will combine to allow for the potential of damaging winds with this activity. Greatest threat looks to be in NE NJ and perhaps the LoHud Valley, which aligns with where SPC continues to place the far western edges of the area in a slight (level 2) risk for severe thunderstorms, and a marginal (level 1) for NYC, western LI, SW CT, the LoHud Valley, and most of NE NJ. The primary threat is the potential for damaging wind gusts being brought down as the weakening convective activity moves in ahead of the cold front in the evening.

In addition to the damaging wind threat, there is the potential for heavy enough rainfall that leads to flooding in some areas.
Precipitable water values are forecast to rise to near 1.5 inches Monday afternoon, or about as high as observed in the local sounding climatology. WPC continues to place the entire area in a marginal risk for excessive rainfall. QPF averages generally between 1 and 1.5 inches, with higher amounts of 2 to 2.5 inches across southern CT. The main flooding impacts will be low-lying, urban and other poor drainage flooding with overall minor impacts. Given slightly higher rainfall potential across S CT with a moist flow off the sound and ocean, opted to hoist a Flood Watch here in collaboration with neighbors.
Nuisance flooding of urban and poor drainage areas appears likely, with perhaps a localized flash flood threat if heavier cells end up training over a narrow corridor. Smaller river and streams may also approach or exceed their banks, but a larger and more widespread riverine flood threat is not expected.
Elsewhere, expect minor nuisance type flooding in urbanized and poor drainage areas at times.

The cold front moves through after midnight, ending the strongest wind gusts as the flow veers westerly and colder air advects in. Still possible the rain could taper as a few wet flakes if timing lines up, mainly north and west of the NYC metro. No accumulation expected should it even occur.

KEY MESSAGE 2
Localized minor coastal flooding and beach erosion remain possible with this system given the expected magnitude of southerly flow and associated wave action.

The combination of low astronomical tides and 1/2 to 1 foot of surge will likely only bring potential for isolated minor coastal flooding to the vulnerable locations of the south shore back Bays of Nassau and western Great South Bay Monday and Monday night. Only the upper end of the latest guidance (90th percentile of Stevens and SNAP-Ex)
is showing this isolated minor threat.

KEY MESSAGE 3
High pressure gradually builds in through the middle of the week, bringing a colder and drier airmass to the area. Temperatures Tuesday through Wednesday night will run about 10 degrees below normal for mid-March. Gusty conditions likely continue on Tuesday.
This combined with the cooler temperatures will keep wind chill values down in the 30s for much of the day.

AVIATION /18Z SUNDAY THROUGH FRIDAY/
***High Impact Aviation Weather Event Late Tonight Through Monday Night***

A strong frontal system impacts the terminals tonight through Monday night.

VFR through 00z. MVFR conditions will begin developing tonight, generally 03-06z, along with a chance of rain. Conditions will then quickly lower to IFR 06-09z with showers. LIFR conditions should then develop through the morning and will likely continue through Monday evening. VLIFR conditions are also possible near the coast with a chance of 1/4SM visibilities, especially in the afternoon/evening.

Periods of showers are expected on Monday with locally heavy downpours possible at times. Isolated thunderstorms are also possible 06-14z. The probability of a thunderstorm increases in the afternoon and evening and having included TSRA in a PROB30 for the NYC metro terminals and KSWF (30 hour TAF sites) after 18z Monday.

E-SE winds 10-13 kt this afternoon with occasional gusts up to 20 kt. ESE-SE winds gradually increase overnight into Monday morning, becoming 10-15 kt with gusts 20-30 kt, strongest near the coast, after 12z. The flow will veer to the S into the afternoon with winds increasing further, becoming 15-20 kt with gusts 25-35 kt. The strongest winds will likely end up at coastal terminals. A few gusts up to 40 kt possible after 21z close to the coast.

LLWS with winds at 2kft 50-60 kt late tonight through Monday.
The strongest LLWS appears likely Monday afternoon and evening when winds at 2kft may be 65-70 kt, especially at coastal terminals.

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

Gusts may be occasional this afternoon.

Amendments likely for timing of lowering ceilings, visibilities, and showers tonight into Monday morning.

Isolated thunderstorms possible after 06z. Adjustments possible to timing of PROB30 for TSRA after 18z Monday.

1/4SM fog possible on Monday, especially in the afternoon and evening.

OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY

Monday Afternoon-Night: IFR to LIFR with showers, possibly heavy at times. Thunderstorms also possible. S winds 15-25 kt with gusts 25-40 kt, highest at the coast. Peak gusts up to 45 kt possible along the coast in the evening. LLWS. Winds decrease slightly and become more westerly late Monday night, gusts 25-35 kt. Showers taper off overnight with improving conditions.

Tuesday: Becoming VFR. W gusts 25-30 kt.

Wednesday-Friday: VFR.

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

MARINE
Gale Warning on all waters late Monday morning through Monday night.

Conditions remain below Advisory criteria through the rest of the day. Winds increase late this evening with SCA conditions developing overnight on all waters as gusts increase above 25 kt with a warm frontal passage. SCA starts on ocean waters 6pm this evening, with non ocean waters at midnight. Winds increase further on Monday, with gales expected by late morning on all waters. Gusts as high as 40 to 45 kt, with ocean seas 14 to 18 ft likely. Thunderstorms possible Monday night, and could produce locally higher gusts to 50 kt.

Strongest of the winds begin to lighten behind a cold front Monday night, with the Gale Warning set to expire at 10Z Tue, then SCA conditions likely linger on all waters through Tuesday with 25 kt gusts, but could potentially continue into Wednesday on the ocean waters with lingering 5ft seas. Sub-SCA conditions then expected thereafter.

OKX WATCHES/WARNINGS/ADVISORIES
CT...Flood Watch from late tonight through Tuesday morning for CTZ005>012.
Wind Advisory from 2 PM Monday to 4 AM EDT Tuesday for CTZ005>012.
NY...Wind Advisory from 2 PM Monday to 4 AM EDT Tuesday for NYZ071>075-078>081-176>179.
NJ...Wind Advisory from 2 PM Monday to 4 AM EDT Tuesday for NJZ006- 104-106-108.
MARINE...Small Craft Advisory from midnight tonight to 11 AM EDT Monday for ANZ331-332-335-338-340-345.
Gale Warning from 11 AM Monday to 6 AM EDT Tuesday for ANZ331- 332-335-338-340-345.
Small Craft Advisory from 6 PM this evening to 6 AM EDT Monday for ANZ350-353-355.
Gale Warning from 6 AM Monday to 6 AM EDT Tuesday for ANZ350- 353-355.