textproduct: New York

SYNOPSIS

Weak high pressure slides offshore with a weak cold front passing through this evening. Low pressure develops along the front, tracking well to the south and east of the area through Sunday morning. High pressure builds southwest of the region Monday into Monday night as a weak low pressure system approaches and eventually moves across from the Great Lakes. High pressure returns for Tuesday building in briefly, before moving offshore by Tuesday night. A cold front moves across Wednesday night. High pressure follows for Thursday. A strong cold front approaches from the west Thursday night and moves across Friday. High pressure returns thereafter into the start of next weekend.

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/

Key Points:

* Winter Weather Advisories have been expanded across most of the local Tri-State region from 10pm tonight through 1pm Sunday.

* 2 to 3" of snow expected across much of the interior, 3 to 5" for NYC/NJ metro and coast, and 4 to 6" for E LI, tonight into Sunday morning. Locally higher amounts possible. A strong polar low (-2 std 500mb height) digs southeast from Ontario into the Great Lakes into tonight. Trend over the last 24-48 hours has been for this feature to take on a slightly more neutral tilt (from positive) as it pivots towards the area tonight into Sunday morning. This will provide a bit more theta-e advection into the area, and also shift the the ULJ slightly farther NW of the region. At the surface, a weak cold front moves through the region this evening, with combination of approaching shortwave PVA and RRQ of 150kt ULJ inducing weak low pressure development along the front across Mid Atlantic this evening, tracking southeast of the 40/70 lat/lon tonight into Sunday AM.

Although surface features are weak, the deep layered lift overnight into Sunday AM (including RRQ of ULJ, and modest mid-level frontogenesis/lift in the snow growth region along the coast), and slightly more depth of moisture for low pressure to work with has resulted in a gradual increase in QPF and snowfall totals over the last 48 hrs.

Good agreement in liquid equivalent of .3 to .5 for coast and .1 to .2 for interior. Main snowfall amount forecast challenge is from northward extent and duration of moderate snow banding, and snow ratios during peak dendritic snow growth late tonight. SLRs should exceed typical 10:1 late tonight into Sunday morning during best snow growth period and dropping 850 hpa temps, with 12-14:1 seeming reasonable late tonight into Sun AM. This has resulted in a general 1" increase in snow amounts across the area. 3-5" likely across much of the coast including NYC/NJ metro, with locally 6" possible. 4-6" across E LI, with locally 7" possible. 2 to 4" across interior. WPC Superensemble and experimental NBM 5.0 have pretty good clustering in these ranges, with reasonable worst case (10% prob of exceeding) a couple of inches higher.

In terms of timing, snow could develop as early as 6-7pm this evening, perhaps mixing with rain for city/coast at onset with air temps in the upper 30s/lower 40s. Steadier snow likely develops after 9pm from w to e, with a steady light to moderate snow from midnight through Sunday morning. Snowfall rates of up to 1/2"/hr likely develop after midnight through mid to late morning for much of the area, with potential for brief 1"/hr rates along the coast from 4am to 11am during best snow growth. This signal is evident in the high-res CAMs, with highest prob across southern and E LI. This will be time period of greatest travel impacts in terms of reduced vsby and snow covered roads with freezing/sub freezing air temps, higher snow rates, and reduced vsby. Initially above freezing air/surface temps for city/coast this evening, dropping below freezing late tonight into Sunday AM, may resulted in icy spots on untreated surfaces.

Steady snow exits from w to e mid to late morning, except early afternoon for far SE areas.

SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/

Key Points:

* Steady snow ending mid to late Sunday morning. A few afternoon snow showers possible. Unseasonably cold with temps remaining below freezing, and high temps nearly 15 degrees below seasonable. * Windy with NW winds gusts 30 to 40 mph and unseasonably cold Sunday night into Monday morning with wind chills near zero city/coast and below zero across interior. Strong polar low (-2 std 500mb heights) pivots into northern New England Sunday into Sunday Night, with trough axis approaching Sunday and then across Sunday NIght.

Steady snow exits from w to e mid to late Sun morning, except early afternoon for far SE areas. Although with approaching shortwave and polar front in the afternoon, could have some scattered snow showers lingering or crossing the region in the afternoon (particularly NW hill terrain and across central and E LI.

Otherwise, unseasonably cold conditions on Sunday with gusty NW flow continuing to advecting in a polar airmass into Sun eve (850mb temps down to -18 to -20 C). This will have temps holding in the mid to upper 20s interior, to upper 20s/lower 30s along the coast. Windchills in the teens.

Coldest airmass of the season ushered in Sunday Night into Mon AM on brisk NW winds of 15-25G30-40mph, with temps falling into the lower teens interior and mid teens coast (upper teens NYC/NJ metro). Windchills of 0 to 5 F for coast, and 0 to -5 F for interior.

LONG TERM /MONDAY THROUGH SATURDAY/

Key Points

* Arctic airmass Monday through Tuesday. Airmass moderates towards midweek. Forecast high temperatures only in the 30s. Monday night lows forecast from teens to lower 20s for most of the area.

* Winds will be NW and gusty Monday with decreasing and more westerly winds Monday night, making for temperatures to feel about 10 degrees colder than the actual temperature.

* Temperatures moderate Wednesday and Thursday, getting back into the 40s with even some 50s for Thursday, before trending colder Friday and Saturday.

* Next main precipitation event Thursday night into early Friday, primarily in the form of rain.

Active forecast period with upper level jet remaining near or within the Northeast for next week. This will provide more steering flow for a more rapid progressive pattern with quick passage of high and low pressure areas. Aloft, there will be a series of troughs that move across the area next week.

An airmass of arctic origin will be moving in from the west Monday into Monday night. The center of high pressure will stay well south and west of the local region. A weak low pressure system from the Great Lakes will approach Monday and eventually move across the region Monday night. A few possible snow showers could result but probabilities are low due to lack of moisture and strength of the aforementioned low pressure system.

High pressure then briefly builds in Tuesday before moving offshore Tuesday night. Airmass will begin to moderate during this time period. A strengthening low pressure area moving eastward within Southeast Canada for midweek will bring an associated cold front towards the local area. This front will move through Wednesday into Wednesday night but its main forcing remains well north of the area. Therefore, no precipitation is forecast with dry conditions prevailing through midweek. Another quick residing high pressure area traverses the region Thursday before another cold front moves across early Friday. The increase in southerly flow ahead of each cold front will advect in warmer air, with Wednesday high temperatures forecast to reach well above freezing for the first time since Saturday, December 13th. Temperatures continue to trend warmer for high temperatures forecast Thursday, getting in the upper 40s to lower 50s for much of the region. These ambient forecast temperatures will make the next main precipitation event mainly rain from Thursday night through early Friday.

Another high pressure area builds in later Friday into the start of next weekend before another cold front approaches for late next Saturday with more chances for rain and snow. Temperatures trend cooler but much of the period will keep mainly dry conditions.

OUTLOOK FOR 18Z SUNDAY THROUGH WEDNESDAY

Sunday afternoon and night: VFR. NW winds 15-20 kt with G25-30kt. Peak gusts up to 35 kt possible NYC metros.

Monday: VFR. NW winds 10-15 kt with G20-25kt, becoming W late afternoon.

Monday night: Mainly VFR with maybe a passing snow shower north/east of the NYC metros.

Tuesday: VFR.

Wednesday: VFR. SW winds G15-20kt in the afternoon.

Thursday: VFR. S winds G15-20kt in the afternoon.

Thursday night: MVFR or lower cond with rain likely, especially after midnight. S winds 15G20-25kt.

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

MARINE

SW SCA gusts into this evening for ocean and souther/eastern nearshore waters. Winds diminish below SCA for a period for all water tonight into Sunday morning as weak low pressure tracks SE of the region.

Winds gradually ramp up in wake of low pressure to SCA for all water Sun AM into early Sun aft, and then marginal gales Sun Night into Monday AM. Gale Watch continues for ocean waters where confidence is highest in frequent gusts, otherwise occasional gusts possible. Seas building to 4 to 7 ft on the ocean waters.

For Monday regarding wind gusts, gales are forecast on the ocean waters with SCA level wind gusts for non-ocean waters. The non-ocean waters have wind gusts dropping below SCA thresholds Monday night while the ocean will have mainly SCA level wind gusts Monday night into early Tuesday. After a brief period of sub-SCA wind gusts for rest of Tuesday into Tuesday night, SCA level wind gusts develop again for the ocean late Tuesday night into Wednesday. Sub-SCA wind gusts forecast for later Wednesday through early Thursday with SCA level wind gusts redeveloping on the waters later Thursday through Thursday night. Some waters, especially the ocean, could have gales Thursday night.

SCA levels seas remain on the ocean Monday through early Tuesday. Brief period of sub-SCA seas then forecast for rest of Tuesday through much of Tuesday night. SCA level seas are also forecast towards mid to late week on the ocean. By Thursday night, parts of LI Sound are also forecast to reach SCA levels.

HYDROLOGY

There are no hydrologic impacts expected through the entire forecast period.

OKX WATCHES/WARNINGS/ADVISORIES

CT...Winter Weather Advisory from 10 PM this evening to 1 PM EST Sunday for CTZ005>012. NY...Winter Weather Advisory from 10 PM this evening to 1 PM EST Sunday for NYZ068>075-078>081-176>179. NJ...Winter Weather Advisory from 10 PM this evening to 1 PM EST Sunday for NJZ002-004-006-103>108. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ331- 332-340-345. Small Craft Advisory from 10 AM Sunday to 6 PM EST Monday for ANZ331-332-335-338-340-345. Small Craft Advisory until 6 PM EST Sunday for ANZ350-353-355. Gale Watch from Sunday evening through Monday morning for ANZ350-353-355.