textproduct: New York

SYNOPSIS

Weak high pressure gradually shifts offshore tonight into the day on Saturday. A strong cold front then approaches Saturday night with an area of low pressure passing south and east of the area during the day on Sunday as the front pushes offshore. High pressure will generally be in control through the middle of next week with a series of frontal systems passing to the north. A frontal system is then expected to move into the area during the Thursday to Friday timeframe.

NEAR TERM /THROUGH SATURDAY/

Weak high pressure south of the area will gradually shift offshore tonight into Saturday. This will allow winds to diminish this evening, and with clear skies this sets up good radiational cooling conditions for at least the first half of the night. Temperatures are expected to drop into the low-mid 20s across much of the region, with a few readings in the teens expected in typically cooler outlying locations. Temperatures could then rise a few degrees towards daybreak as high clouds begin to overspread the area.

Dry conditions are expected during the day on Saturday with steadily increasing clouds ahead of the next system. With the high offshore, west-southwest flow will develop, allowing highs to rise to around 40 degrees, which is still a few degrees below normal for mid-December.

SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/

Key Points:

* 1 to 4 inches of snow are expected across the area Saturday night into Sunday morning, with the highest snowfall totals expected across Long Island.

* A Winter Weather Advisory has been issued for Long Island, New York City, and portions of Northeast New Jersey from 10pm Saturday night through 1pm Sunday.

A potent shortwave diving from the Upper Midwest to the Ohio Valley will help deepen the upper trough as it pushes east towards the area Saturday night into Sunday morning. This will help induce the development of surface low pressure well south and east of the local area by Sunday morning. While this system looks to be a quick mover, good upper level support and enough cold air in place should be enough to produce an advisory level snow event across parts of the area.

Expect precipitation to begin to break out across the region after 7pm Saturday night. With With temperatures still a few degrees above freezing along the coast at the start, can't rule out a mix of rain and snow initially, but expect this to transition fairly quickly to all snow for the entire forecast area. Snow will then continue through the overnight hours, with the steadiest snow expected between midnight and 7am Sunday morning. Thereafter, snow is expected to quickly taper from west to east as the surface low pulls away from the region, with any lingering snow clearing eastern Long Island by early afternoon. Snowfall totals will range from 2-4 inches across the Advisory area, with the highest amounts expected across central and eastern Long Island, with 1-3 inches of snow expected elsewhere.

With another shot of cold air arriving behind the system, highs on Sunday will remain within a few degrees of freezing with gusty northwest winds developing in the afternoon. Temperatures Sunday night will fall into the teens across the entire area, with wind chill values in the single digits.

LONG TERM /MONDAY THROUGH FRIDAY/

Key Points:

* Much below normal to start the week, then warming up to above normal for the second half of the week.

* Chance of rain Thursday into early Friday with no hydrologic impacts anticipated.

A departing upper trough on Monday will be followed by a nearly zonal flow across the Lower 48. There are some differences in the operational models with the potential for amplification of an upper trough over the Upper Midwest and Great Lakes region during the second half of the week. The latter seems to hinge on the interaction of multiple streams of energy moving in from the North Pacific along with energy rounding the polar vortex, which will be bottled up well to the north. Thus, looking at a week where temperatures will start off well below normal (10-15 degrees), but ending on a warm note with highs forecast to top out in the upper 40s to lower 50s Thursday. Some cooler air arrives on Friday, but due to the aforementioned complexities, the magnitude is a bit uncertain. The NBM (which was followed) returns us back to normal on Friday following the passage of a frontal system. A consensus approach seems prudent at this time.

Outside of snow flurries and/or a snow shower Monday night, the next chance of precipitation will be Thursday/Thursday night in the form of rain. Warm advection ahead of this system brings in too much warm air to support frozen precipitation.

OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY

Saturday night: Snow moving in late evening and overnight with MVFR to IFR, possibly LIFR late at night.

Sunday: MVFR to IFR, possibly LIFR at times, in snow, mainly in the morning. Snow tapers off from west to east afternoon into early evening. Improving conditions afternoon into evening with VFR returning. NW winds gust around 25kt in the afternoon and night with peak gusts around 30kt.

Monday: Mainly VFR. NW winds G20-25kt. Gusts lower at night with some gusts to 20kt.

Tuesday-Wednesday: VFR.

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

MARINE

SCA extended to 10 PM on the ocean waters east of Moriches Inlet.

Winds and seas will continue to subside through the night as high pressure builds in from the west. Other than a few gusts to near SCA criteria on the ocean waters Saturday afternoon, conditions on the waters will remain quiet until Sunday. Winds will shift to the NW following a cold frontal passage with gusts 25-35 kt on the ocean and 25-30 kt elsewhere beginning Sunday afternoon. At the same time ocean seas will increase to 5-7 feet.

Expect SCA conditions on Monday with a gradually diminishing NW flow. There could be a secondary bump in winds Monday night as a frontal system passes to the north, prolonging the SCA on the ocean waters a bit longer. Sub-SCA conditions are then forecast for all waters Tuesday as high pressure builds in from the west.

HYDROLOGY

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

OKX WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory from 10 PM Saturday to 1 PM EST Sunday for NYZ072>075-078>081-176>179. NJ...Winter Weather Advisory from 10 PM Saturday to 1 PM EST Sunday for NJZ006-106>108. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ350.