Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 171349 AFDOKX Area Forecast Discussion National Weather Service New York NY 849 AM EST Mon Dec 17 2018 .SYNOPSIS... Low pressure deepens as it moves near Nova Scotia through tonight with a cold front moving across the local region tonight as well. Deep low pressure over the Canadian Maritimes Tuesday gives way to high pressure through mid-week. Another low impacts the area Thursday night through Saturday. Weak high pressure then returns for Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Any remaining area of light rain or drizzle is confined now to SE Connecticut and near the Twin Forks of Long Island, though observations beneath the returns indicate little if any is reaching the ground. Temperatures and dewpoints were within a few degrees comparing forecast and observed values. Expecting after the surface low moves farther east of the region, drier conditions to move into place but clouds will remain and increase in the late afternoon into early evening. There will be a strong vorticity maximum passing through with a shortwave. There will be cyclonic flow aloft. It may result in a few rain or snow showers. A lot of model output with precipitation has nothing across the local region, so boundary layer may be too dry for any precipitation to reach surface. The temperature forecast used consensus as opposed to blend of MAV, MET, ECS as the consensus gave a solution for max temperatures a few degrees less. Models all show in 850mb fields significant cold air advection with 850mb temperatures dropping about 6 to 8 degrees C from this afternoon until early this evening. Winds are expected to increase significantly into the afternoon.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... The pressure gradient will tighten more tonight with low pressure deepening as it moves into Nova Scotia in contrast with the high building to the west of the region into the Ohio Valley. Cold air advection continues as seen with 850mb temperatures. The 850mb temperatures decrease by about another 6 degrees C tonight. Used consensus for min temperatures tonight. Less spatial variance is seen due to the well mixed boundary layer and therefore gusty winds. The high starts to build in from the west on Tuesday. More subsidence is seen from the ridging trend aloft and negative vorticity advection seen in the mid levels. This will promote more sunshine. However, another gusty day expected as the pressure gradient remains rather tight. With a well mixed boundary layer, adiabatically mixing down from much colder 850mb temperatures will result in much colder surface temperatures compared to the previous day despite the extra sun. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Deep-layered ridging Tuesday night through Thursday morning will keep any rain out of the forecast. A surface high approaches during this period, with its axis shifting through here around Wednesday morning. High temperatures on Wednesday will be near normal, then above normal on Thursday. Some rain ahead of the next system may sneak into the Tri-State Area by late in the day, but the trend has been for the likelihood of rain starting Thursday night. Low pressure is progged to move up along the Appalachians Thursday night night into Friday as it strengthens. Rain is expected here during this time, and it could potentially be heavy at times on Friday as a low level jet enhances lift and a fairly strong upper jet streak approaches. The storm`s cold front passes through Friday night with showers possible, then a drying trend follows for the upcoming weekend. Still a low chance of a passing shower on Saturday, but looking dry for Sunday. High temps above normal for Friday and Saturday, then returning closer to normal on Sunday. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Intensifying low pressure east of Nantucket will move northeast today and then north into the Canadian Maritimes tonight. A cold front will move across from late afternoon into early evening. Residual MVFR will improve to VFR thru 15z. Winds still expected to back to around 290-300 true, with the strongest winds late this afternoon into tonight with the cold fropa. Sustained winds increase to around 20 kt with gusts 30-35 kt. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component fcsts, can be found at: http:/ KJFK TAF Comments: No unscheduled AMD expected. The afternoon haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KLGA TAF Comments: No unscheduled AMD expected. The afternoon haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KEWR TAF Comments: No unscheduled AMD expected. The afternoon haze potential forecast is GREEN, which implies slant range visibility P6SM outside of cloud. KTEB TAF Comments: No unscheduled AMD expected. KHPN TAF Comments: No unscheduled AMD. KISP TAF Comments: No unscheduled AMD expected. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .Tuesday...VFR. NW winds 15-20G25kt. .Tuesday night...VFR. NW winds 10-15G20kt in the evening. .Wednesday-Thursday...VFR. .Thursday night...Rain with MVFR or lower conds developing. E-SE winds G20kt late. .Friday...Rain with MVFR or lower conds. SE winds G20kt becoming S in the afternoon. LLWS. && .MARINE... SCA in effect on the non-ocean waters with gales on the ocean waters. Wind gusts start picking up late morning into this afternoon. The non-ocean waters have gales for tonight through Tuesday morning with conditions will return back down to SCA levels Tuesday afternoon. The ocean prevails with gales through Tuesday. Winds diminish Tuesday night as high pressure builds over the waters. All waters should fall below advisory criteria by Wednesday morning. Then as the center of high pressure nears and passes through, tranquil conditions for Wednesday and Thursday. Low pressure then approaches and probably brings at least SCA conds Thursday night into Friday. A strong enough low level jet may also bring the threat of gale force wind gusts during Friday. Confidence is not high enough for a mention in the HWO at this time. && .HYDROLOGY... Mainly dry conditions expected through Thursday. The next chance for significant rainfall of at least a half an inch is expected to occur late in the week (Thursday night- Friday). Still too early to determine if there will be any hydrologic concerns with this potential late week event. && .EQUIPMENT... NYC Central Park winds are out of service until further notice. Loss of data is due to a severed cable. Parts are on order. NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ330- 335-338-340-345. Gale Warning from 6 PM this evening to noon EST Tuesday for ANZ330-335-338-340-345. Gale Warning until 6 PM EST Tuesday for ANZ350-353-355. && $$ SYNOPSIS...JC/JM NEAR TERM...MD/JM SHORT TERM...JM LONG TERM...JC AVIATION...12/Goodman MARINE...JC/JM HYDROLOGY...JC/JM EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.