Marine Weather and Tide Forecast for Norwalk, CT

KEY MESSAGES
1) Areas of fog and black ice still possible for parts of the area tonight.

2) Snow showers expected on Sunday.

3) Multiple waves of low pressure will move through the area Tuesday through the start of next weekend. Expect a prolonged period of wet and mostly cloudy conditions with above normal temperatures.

DISCUSSION

KEY MESSAGE 1
MOS and time-lagged NAM/RAP guidance suggest greatest potential for fog will be across Long Island, NYC, and SW CT. for several hours from about 9-10 PM until 1-2 AM as a cold front moves through and a drying northerly flow in its wake scours out low level moisture. With the expected timing and temperatures, best potential for freezing fog would be across eastern Long Island.

KEY MESSAGE 2
No advisories are currently anticipated for snow or wind chills.

Weak shortwave trough accompanied by some H8 theta-e advection and H7 frontogenesis will move through daytime Sunday, mainly during the morning and early afternoon. Have kept likely PoP which is above NBM and MOS guidance, and lowered accumulations slightly, with up to an inch well inland and more on the order of a dusting for the NYC metro and coastal sections.

Precip should be exiting eastern Long Island/CT by late afternoon. the end of the day. Thermal profiles support snow as wet bulb temps should be at or below 32 for the duration of the event. Minor impacts expected for the most part.

Colder air filters in from the north during Sunday night with low temps from the upper single digits well inland, to the teens elsewhere. Wind chills should bottom out around zero well inland and in the single digits elsewhere. Highs for Monday only from the mid 20s to lower 30s in most spots, and get to within 3 degrees of record low maxes for the date at Newark, JFK, and Islip.

KEY MESSAGE 3
The first chance of precipitation next week comes on Tuesday. As Arctic high pressure shifts to the east, a wave of low pressure looks to pass through. Because of the cold air in place Tuesday morning, this precipitation likely starts off as snow across the interior with a snow or rain/snow mix at the coast. We will quickly warm up so through the day the area will gradually transition to all plain rain. There are still some timing differences with just how early the precipitation will start and this will end up affecting p-types and any sort of accumulation.
At this time, under an inch of snow expected. Even the NBM 4.3 and 5.0 90th percentiles for snow accum show less than an inch for much of the area with the exception of the Lower Hudson Valley where it shows a few inches of accumulation.

Once the Arctic airmass shifts east, a warming trend will begin, with above normal temperatures expected by Wednesday.
Timing and location differences with additional waves of low pressure continue in the latest guidance. While prolonged wet conditions are expected, the period will not be a washout by any means. There are chances of rain each day, but this is largely due to the spread in guidance. From Tuesday through Saturday the latest NBM has a total of about 0.75 to 1.00 inches of QPF.

AVIATION /21Z SATURDAY THROUGH THURSDAY/
High pressure off the northeast coast weakens as a cold front approaches through this evening and moves through tonight. High pressure builds in from the west late Sunday into Sunday night.

Mainly VFR until Sunday morning with light snow. There is a chance of MVFR ceilings in stratus during the evening before a cold front passes through the terminals, and now included a TEMPO for this possibility. There also may be visibility restrictions in fog, however, confidence is low for fog and not included in the forecast.

Light snow Sunday morning into the early afternoon west, and into late afternoon far east, with generally MVFR conditions and a possibility of IFR visibilities in light snow, and maintained the TEMPO group for the lower conditions. Once the snow ends VFR develops.

Winds S/SW 10 kt or less ahead of a cold front, becoming light and variable as the front nears, then NW/N 10 kt or less after the cold front.

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

Low confidence of fog development this evening, with a period of stratus more likely. There is a chance that stratus does not develop and now included a TEMPO for the possibility.

Moderate confidence with the timing of the snow for Sunday, and a brief period of IFR visibilities.

OUTLOOK FOR 18Z SUNDAY THROUGH THURSDAY

Sunday afternoon: MVFR cigs and IFR vsbys in light snow, ending west to east 18Z to 21Z. Becoming VFR. N/NW winds G15-20 kt.

Monday: VFR.

Tuesday: MVFR or lower with a rain/snow mix in the morning, becoming plain rain during the afternoon and into the evening south to north. S wind G15-20 kt possible.

Wednesday - Thursday: MVFR, possibly IFR, with a chance of rain. Thursday S wind G15-20 kt possible.

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

MARINE
Sub-advisory conditions expected for the most part through Tuesday. Conditions may get close for a time on the ocean late Sunday night, with N flow gusting over 20 kt and seas up to 4 ft. Light freezing spray expected on the ocean waters Sunday night into Monday morning as well.

There are several weak waves of low pressure that will pass through, with winds and seas on the ocean getting close to SCA criteria Tuesday night into Wednesday, and then again at the end of the week.

OKX WATCHES/WARNINGS/ADVISORIES
CT...None.
NY...None.
NJ...None.
MARINE...None.