textproduct: New York

SYNOPSIS

A cold front moves offshore through this evening. High pressure briefly returns tonight into Friday. A winter storm impacts the area late Friday into Saturday morning. A strong frontal system impacts the area late Sunday through Tuesday, with a weaker system moving through Wednesday into Thursday.

NEAR TERM /UNTIL 6 AM FRIDAY MORNING/

Key Messages:

* A cold front moves offshore through this evening

* Much colder air moves into the region with high pressure building down from southeast Canada.

Mild and breezy conditions for the rest of the afternoon will turn much colder tonight. Arctic air will advect south out of southeast Canada with high pressure building southward. Dew points will lower significantly and should be in the single digits overnight with temperatures bottoming out in the teens inland and lower 20s closer to the coast. Breezy conditions also expected this evening with gusts 25-30 mph, gradually diminishing overnight. Wind chills by early Friday will be in the single digits to lower teens closer to the coast.

SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/

What's Changed: Winter storm watches have been converted to warnings. A winter storm warning has been issued for eastern Suffolk and New Haven counties and a winter weather advisory has been issued for Middlesex county.

Key Messages:

* A winter storm will impact the area late Friday through Saturday morning.

* The heaviest snow is expected to occur Friday evening (after 4 pm through about 1 am Saturday with lighter snowfall rates early Saturday. Travel will be impacted Friday evening into early Saturday morning.

* Snowfall accumulations range from 4 to 8 inches in much of the warning area, 3 to 5 inches in the Advisory, and 1 to 3 just outside the Advisory in New London county.

Global models and their associated ensemble systems continue to highlight a quick moving shortwave rounding a strong upper ridge centered over the central plains, approaching the local area from the northwest Friday afternoon. At the surface, a cold high pressure centered over Quebec heads to the east as a surface low traverses the OH Valley, through PA and generally south of the local forecast area by 12Z Saturday. This will allow for a cold and dry arctic airmass to remain in place at the start as the shortwave and sfc low pressure approach Friday afternoon.

The modeling has shown slight adjustments over the last 24 hours, but the main message has remained consistent that strong frontogenesis and lift with couple with the left exit region of an upper jet streak to bring in widespread snow across the area late Friday through early Saturday morning. There has been some concern with the warm advection aloft, around H7, bringing in a a chance of sleet mixing in with the snow. This concern was indicated by the NAM, but the 12z has backed off somewhat and trended back south and west. Most of the rest of the guidance suite continues to be in good agreement with keeping any mixing out of the area. Warm advection does tend to come in a bit stronger than modeled, so felt it was warranted to introduce a slight chance of sleet for portions of NE NJ Friday night. This does not change the message and is currently not expected to impact snow accumulations.

The majority of the significant snowfall accumulation will occur Friday evening and the first half of the night when the strongest thermal forcing (FGEN), middle level omega, and large scale synoptic lift coincide. These ingredients will lead to a band of heavy snow. Where this band sets up is still a bit uncertain, but guidance has largely been hinting at somewhere from the NYC metro through western Long Island and southwest Connecticut. The heavy snow band will gradually subside overnight as the lift weakens and saturation aloft begins to wane. Light snow accumulation is still expected through early Saturday morning, although the rates will likely be much lower.

The event has come into the scope of the higher resolution models and they differ on the placement of the banding. However, they show the potential of this event well. The 12z HREF indicates a respectable probability (50-70%) of greater than 1 inch per hour rates beginning around 6-7pm from NYC metro on NW and then shifting south and east through 11pm. The 12z HREF also has probabilities of greater than 2 inch per hours of around 20-40 percent in the vicinity of the NYC metro, western Long Island, into the Lower Hudson Valley. This leads to growing confidence in heavy snowfall rates for several hours after sunset into the first part of the night as the heavy band moves across the region.

While there is still uncertainty in the placement of the banding, there is enough confidence to upgrade the winter storm watch to a warning. We have also added New Haven and eastern Suffolk into the warning as guidance has trended towards heavier snow potential a bit further east. It should be noted that the eastern portions of the north and south fork will likely not reach warning criteria, but enough of the western half of the zone could easily see the 6 inch criteria met.

Snowfall Accumulations: Forecast accumulations over the last 24 hours have not changed much with just minor adjustments and a slight shift eastward with the 6 inch amounts. Overall, 4 to 8 inches are forecast in the warning (average of 6 inches) with the exception of the forks of Long Island likely coming in lower. In the Advisory in Middlesex county, 3 to 5 inches forecast with 2 to 4 in New London. A reasonable worse case scenario in the warning area continues to be about 8-10 inches and around 6 outside the warning. The higher amounts are possible if banding were to put down a bit more snow or linger longer over specific areas than currently anticipated.

If the forecast verifies, Central Park will receive its first snowfall of greater than 4 inches since January 2022. In the January 28-29, 2022 storm 8.3 inches was observed.

Snowfall rates: Peak rates of 1-2 inch per hour are expected in heavier snow bands. There is a low chance rates could come briefly exceed 2 inches per hour in heaviest snow in banding, right now this appears isolated.

Snow characteristic: There is likely going to be variability with snow ratios throughout the event, but the snow may begin a bit drier and become wetter as the event wears on. The banding potential also complicates this as within the band ratios will likely be high but in areas surrounding the band could be lower.

Some light snow or flurries may continue Saturday morning before tapering off by midday. Any additional accumulation after 12z will be insignificant and likely just trace amounts. Clouds may linger into the afternoon, but we should begin seeing some clearing in the afternoon from north. Highs will struggle to rise above freezing, but should briefly get there closer to the coast. Cold temperatures remain in place Saturday night with lows in the teens inland to around 20 near the coast.

LONG TERM /SUNDAY THROUGH THURSDAY/

Key Messages:

* A strong frontal system will likely bring plain rain and gusty winds to the area late Sunday into Tuesday, but could potentially bring a brief period of freezing rain to the interior at the onset.

* A weaker frontal system follows Wednesday into Thursday, but likely moves through dry.

The main story of the long term period is the strong frontal system that will impact the area late Sunday into Tuesday. The center of the low is progged to move over the Great Lakes region and deepen rapidly as it continues into northern New England. Right now the main concern with this system is how much, if any, freezing rain it could bring to the interior. As the warm front approaches and warmer air moves in aloft, the ground across the interior likely stays right around freezing for some time, especially after being primed by a cold airmass for a ~3 days. While there are differences in the exact extent or duration of any freezing rain in the latest guidance, confidence is high enough to add chance of freezing rain to the forecast for the interior. It is too early to talk specific amounts, but the latest NBM 90th percentile for ice is all under a tenth of an inch. Temperatures will likely be rising right through Sunday night so current forecast has a changeover to all plain rain after midnight and then continuing as all plain rain through Monday.

As this system departs, gusty winds are expected. Gusts early Tuesday could reach 35 to 40 mph out of the northwest. Additionally, with a colder airmass building in, wind chill values on Tuesday will be in the teens.

A weaker frontal system moves through thereafter and is not expected to bring any significant impacts at this time.

OUTLOOK FOR 21Z FRIDAY THROUGH TUESDAY

Friday Night: LIFR, possibly VLIFR, in snow Friday night across the region. Low potential (<30%) for IP to mix in Fri Night for NYC/NJ metro and LI terminals.

Saturday: IFR with AM snow, low potential (<30%) for IP to mix in Sat AM for NYC/NJ metro and LI terminals. IFR conditions may linger through the afternoon with a mix of light snow/FZDZ. Improving conditions late Sat into Sat eve.

Sunday: MVFR/IFR with rain developing in the afternoon, continuing overnight.

Monday: MVFR/IFR with rain AM, improving in the afternoon. SW/W winds G25-30 kt.

Tuesday: VFR. W winds G25-30 kt.

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

MARINE

SCA conditions continue through tonight with the ocean running a bit into Friday morning due to lingering elevated seas. Conditions then fall below SCA into Friday night. There is chance winds increase for an SCA later Saturday on the ocean. Otherwise, conditions remain below SCA into Sunday night.

At least Small Craft Conditions are likely Monday through Tuesday night with the next frontal system. There will also be a period in there Monday night through Tuesday where Gale conditions are possible. Peak winds and waves look to be early Tuesday morning when 35 to 40 kt gusts are possible on the ocean waters and up to 35 kt are possible elsewhere. Additionally, ocean seas look to top out around 8-12 feet, with waves on the LI Sound reaching 5-7 feet.

While conditions lower after that, there is potential for Small Craft conditions to hang around much of the week.

HYDROLOGY

No hydrologic impacts are expected into early next week.

OKX WATCHES/WARNINGS/ADVISORIES

CT...Winter Storm Warning from 4 PM Friday to 1 PM EST Saturday for CTZ005-009. Winter Storm Warning from 7 PM Friday to 1 PM EST Saturday for CTZ006-010. Winter Weather Advisory from 7 PM Friday to 1 PM EST Saturday for CTZ007-011. NY...Winter Storm Warning from 4 PM Friday to 1 PM EST Saturday for NYZ067>075-078-080-176>179. Winter Storm Warning from 7 PM Friday to 1 PM EST Saturday for NYZ079-081. NJ...Winter Storm Warning from 4 PM Friday to 1 PM EST Saturday for NJZ002-004-006-103>108. MARINE...Small Craft Advisory until 4 AM EST Friday for ANZ331-332-335- 338-340-345. Small Craft Advisory until 10 AM EST Friday for ANZ350-353-355.