textproduct: New York

WHAT HAS CHANGED

A Cold Weather Advisory has been issued for Friday night.

A winter storm watch has been issued for late Saturday night into Monday afternoon.

KEY MESSAGES

1.) An Arctic air mass settles into the region late Friday, with subfreezing temperatures likely to persist through at least mid next week. Some of the coldest air will be Friday night. A Cold Weather Advisory has been issued for the entire area for that time frame for minimum wind chill values between -5 and -10.

2.) Confidence high enough to issue long lead time winter storm watches for the entire CWA.

KEY MESSAGE 2

As strong high pressure retreats to the NE late Sat night into Sunday, an expansive winter storm will impact the area from then into Mon. Primary low pressure moving into the TN valley on Sunday should dissipate while a secondary low forms near Cape Hatteras and the VA capes, and then moves to a position just inside the 40N/70W benchmark. Snow should begin in the NYC metro area after midnight Sat night and spread NE to the rest of the CWA by daybreak, with some accumulation of 1-2 inches possible by daybreak for the NYC metro area. Heavy snow is then likely daytime Sunday into Sunday evening via strong front-end H7-8 frontogenetic and thermal forcing aided by an anticyclonic upper jet to the north. Given the cold air mass in place, snow ratios look to be on the high side (15:1) at the onset, and then settle down a little closer to 12:1 as heavier precip arrives and the low to mid levels slowly warm.

Depending on the ultimate track of the system, it remains possible enough warm air could intrude aloft to force a brief mix with sleet and/or freezing rain Sunday night, especially for NYC and Long Island. Have only mentioned a slight chance of this occurring, and at any rate the damage will have been done well before then as far as meeting 6+ inch snowfall amounts.

Total QPF for the event should be roughly between 1.0-1.5 inches. Watch mentions potential for at least 6-12 inches with potential for 12 or more inches. The above QPF with higher snow ratios yields widespread potential accumulations of over a foot.

As the coastal system exits north and east into Monday, the deepening low and an inverted surface trough may allow for some additional light accumulation much of the day as well, though heavy snowfall should be over by that point.

Coastal flooding does not appear to be a big issue with this storm. NYHOPS guidance does show potential for minor flooding on the back bays of Nassau late Sunday night, while bias-corrected STOFS shows water levels at nearly all sites remaining below minor flood thresholds as tidal departures remain below 2 ft. Uncertainty is on the high side due to the long lead time, and guidance can sometimes be slow to catch up with unfolding longer term events, so if departures are closer to 2.5 ft, then some minor flooding may be possible at the times of high tide late Sunday night and again Mon afternoon.

OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY

Friday Afternoon: VFR. W winds G25-30kt in the afternoon, becoming NW in the evening.

Saturday: VFR. NW winds G15-20kt. mainly in the morning.

Saturday night into Monday: Snow developing from south to north late Saturday night, ending on Monday. NE winds 10-15kt G20-25kt, becoming NW on Monday.

Tuesday: VFR. W winds G20kt.

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

MARINE

A Freezing Spray Advisory has been issued for the ocean and SOund for Friday night. A combination of elevated seas, 20-30 kt winds and air temps in the teens will result in moderate freezing spray (accumulation of 0.3 inches to 0.8 inches per hour). The Overland Technique was mainly followed, but Stallabrass and MINCOG models as viewed on OPC's Freezing Spray Guidance Page are also showing moderate vessel icing rates. Other bay areas and the New York Harbor will likely not see waves high enough to result in moderate vessel icing, but some light icing can not be ruled out.

SCA on the ocean remains in effect through Friday night. Gusts up to 25 kt are possible most of tonight, but then a lull may be possible very late tonight into Fri morning. Winds and seas pick back up on Fri with conditions close to gale, so an upgrade to a Gale Warning can not be ruled out. On all other waters a Small Craft Advisory remains in effect from Friday through Friday night for 25-30 kt wind gusts. Conditions look to finally fall below advisory criteria on Saturday.

As a winter storm affects the area early next week, NE gales may be possible Sunday afternoon on the ocean, and on all waters Sunday night. There may be a lull (with SCA cond) before NW gales resume late Mon afternoon on the ocean waters and on all waters Mon night. These gales may linger into Tue on the ocean. Following that, SCA cond likely on all waters into Tue night.

CLIMATE

Record Low Maximum Temperatures:

January 24: KEWR: 15/1936 KBDR: 20/2014 KNYC: 6/1882 KLGA: 18/1987 KJFK: 19/1987 KISP: 19/2014

OKX WATCHES/WARNINGS/ADVISORIES

CT...Cold Weather Advisory from 10 PM Friday to 10 AM EST Saturday for CTZ005>012. Winter Storm Watch from late Saturday night through Monday afternoon for CTZ005>012. NY...Cold Weather Advisory from 10 PM Friday to 10 AM EST Saturday for NYZ067>075-078>081-176>179. Winter Storm Watch from late Saturday night through Monday afternoon for NYZ067>075-078>081-176>179. NJ...Cold Weather Advisory from 10 PM Friday to 10 AM EST Saturday for NJZ002-004-006-103>108. Winter Storm Watch from late Saturday night through Monday afternoon for NJZ002-004-006-103>108. MARINE...Small Craft Advisory from 10 AM Friday to 6 AM EST Saturday for ANZ331-332-335-338-340-345. Freezing Spray Advisory from 6 PM Friday to 6 AM EST Saturday for ANZ331-332-335-350-353-355. Small Craft Advisory until 6 AM EST Saturday for ANZ350-353. Small Craft Advisory until 6 AM EST Saturday for ANZ355.