Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 090548 AFDOKX Area Forecast Discussion National Weather Service New York NY 1248 AM EST Fri Dec 9 2016 .SYNOPSIS... A cold front will move across Friday afternoon. High pressure will builds over the area Saturday and Saturday night, then slowly retreat to the northeast early next week. A stationary front will set up south of Long Island by late Sunday and remains into Monday night, as a wave of low pressure rides along it. High pressure will build in Tuesday and Tuesday night, followed by a coastal low passing to the southeast Wednesday and Wednesday night. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Brisk W-NW flow and mostly clear skies outside of a bit of lake streamer strato-cu. Temps tonight should fall to just below freezing in NYC (and at Central Park for the first time since April 10th), and into the 20s elsewhere. Wind chills will be in the teens and 20s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Brisk NW flow will continue, gusting to 35 mph at times. Another weak shortwave/cold front will move across Friday afternoon, reinforcing the cold air already in place. Low level flow off Lake Ontario should bring instability clouds, also scattered snow showers well north/west of NYC and flurries elsewhere. Highs across the area should remain in the 30s, which at Central Park would be the first time since March 4th that the temperature failed to break 40. This would also be the 2nd longest stretch on record at the park with highs 40 or greater. Meanwhile wind chills will be in the teens to near 20. Clearing skies expected Fri night, but remaining brisk and cold, with lows 15-20 well inland and across the Long Island Pine Barrens, and 20-25 elsewhere. Wind chills will again be mainly in the teens. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A weak northern stream shortwave passes on Saturday, the atmosphere above 700 hPa will be to dry to support any measurable precipitation, however some stray flurries cannot be completely ruled out. Highs Saturday were based on a blend of MAV/MET/ECS guidance, NAM 2-meter temperatures and a mix down from775-750 hPa per BUFKIT soundings. Highs should be around 5-10 degrees below normal. Zonal flow sets up aloft Saturday night, and with no shortwaves forecast to be embedded in the flow, it should be dry. Lows Saturday night were based on a blend of MAV/MET guidance and NAM 2-meter temperatures and should be around 5 degrees below normal. For Sunday-Monday night the models are coming into better agreement that fast zonal flow will produce a weaker/flatter (more sheared) system moving in from the Intermountain West starting Sunday morning. The reduced amplification will result in weaker warm advection ahead of the system, with the warm front now likely staying S of Long Island through the event, with a secondary low tracking to the S of Long Island along the front. Northern stream ridging ahead of the system will support the forming of a high over SE Canada which should server as a source for low level cold air by Monday (NE- E flow over the region - typical of a cold air damming pattern). In terms of sensible weather, the aforementioned shortwave ridging passing to the north Sunday should hold off anything other than very light precipitation into Sunday afternoon - with snow across the interior and rain elsewhere. The precipitation will become more widespread and steady Sunday night and should chance to all snow from N to S Sunday evening across the Tri-State. Snow continues into Monday, with precipitation mixing with then changing to rain over Long Island and at least Southern portions of NYC and maybe coastal SW CT Monday morning and then to all rain Monday afternoon, except for maybe far Northern portions of the CWA where a rain/snow mix could linger. Precipitation should taper off from W to E Monday night as the low exits to the southeast of Cape Cod mainly as Snow N of Long Island Sound and Rain to the south. Northern Stream ridging builds in Tuesday then exits to the east Tuesday night, keeping things dry. The extended forecast then becomes uncertain Wednesday/Wednesday night in terms of timing/track of a coastal low passing to the southeast. It should be cold enough for interior regions to see mainly snow (if they see any precipitation) and coastal areas a wintry mix. There is also some question on how cold it will be on Wednesday - which plays into precipitation type. Thursday should be dry and cold on WNW-NW flow aloft. The degree of cold is in question - with the GFS having 850 hPa temperatures at or below -18C and the ECMWF at or below -10C. This is the difference between highs mid 30s to around 40 ECMWF and around 20-mid 20s GFS. There is more evidence pointing towards the colder vice warmer edge of the things, so weighed more towards the GFS (temperatures mainly in the mid-upper 20s). Gusty NW winds should produce wind chills Thursday afternoon from around 10 degrees across the northern interior to lower-mid teens across urban NE NJ/NYC/Long Island. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... VFR through the TAF period. High pressure builds through Friday. NW winds continue through tonight. Gusty winds will continue tonight and may relax somewhat overnight. Gusts could become more occasional overnight, mainly in the outlying terminals, while there may not be any gusts for other outlying terminals (specifically KISP, KSWF and KGON). Winds and gusts will increase after sunrise Friday with gusts 25 to 30 kt late morning into the afternoon. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .Friday afternoon...Flurries or snow showers possible mainly NW of NYC metro. NW winds G20-30KT. .Saturday...VFR. .Sunday...Mainly VFR. Chance of light snow late. .Sunday night and Monday...MVFR or IFR in snow Sunday night, changing to mixed precipitation near the coast on Monday. .Tuesday...Mainly VFR. && .MARINE... SCA in effect for all waters. There could be a few gusts up to 35 kt on the ocean and Eastern LI Sound late tonight. Gale Watch has been issued for the ocean for Friday into Friday night as potential for gales increases. Winds should gradually diminish Fri night, with SCA conds remaining only on the ocean and the eastern Sound/bays after midnight. SCA conditions should return to all waters on Saturday, and remain on the coastal ocean waters into Saturday night. Winds should subside to 10 kt or less on all waters Sunday morning, then increase to 10-15 kt by Sunday night and remain so over the ocean waters through Tuesday. There is a chance for gusts to around 25 kt on the coastal ocean waters Sunday afternoon and night. On the non-ocean waters winds should be 10 kt or less Monday-Tuesday, except maybe reaching 15 kt over eastern Long Island sound on Monday. && .HYDROLOGY... There is the potential for 0.5-1 inches of liquid equivalent precipitation from late Sunday into Sunday night. && .EQUIPMENT... New York City NOAA Weather Radio NWR transmitter KWO-35 is back in service. Central Park (NYC) observations (METAR) are still unavailable due to an area power outage. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 AM EST Saturday for ANZ330-335- 338-340-345. Gale Watch from 6 AM EST this morning through late tonight for ANZ350-353-355. Small Craft Advisory until 6 AM EST early this morning for ANZ350-353-355. && $$ SYNOPSIS...Goodman/Maloit NEAR TERM...Goodman SHORT TERM...Goodman LONG TERM...Maloit AVIATION...JP MARINE...Goodman/Maloit HYDROLOGY...Goodman/Maloit EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.