Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 171149 AFDOKX Area Forecast Discussion National Weather Service New York NY 649 AM EST Tue Jan 17 2017 .SYNOPSIS... A warm front slowly approaches from the southwest through tonight. This passes just south of Long Island late tonight into Wednesday with a small area of low pressure moving across. The low moves east of the region Wednesday. High pressure builds into the region on Thursday as offshore low pressure gradually moves east. The high weakens on Friday followed by a weak wave of low pressure passing to the south Friday night. High pressure returns this weekend before the next low pressure and associated frontal system impacts the area early next week. && .NEAR TERM /THROUGH TONIGHT/...
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Still dry across the region with any weak echoes evident on radar being mainly over Orange County where temperatures are in the low to mid 30s. The freezing or below temperatures may be more isolated with associated freezing drizzle areas. Window should be brief as more warming is anticipated by late this morning allowing for all precip to be plain rain. The main focus will be temperatures and approaching precipitation ahead of a warm front. This will be associated with increasing isentropic lift, maximizing this afternoon into tonight with an increasing SE low level jet. Upper level subtropical jet will be approaching with its left front quad, enhancing lift late today through tonight. For temperatures today took the HRRR/NAM12 average and tonight took a blend of MAV/MET/ECS. SW flow leading into this morning and lowering and thickening clouds should keep temperatures nearly steady with a slight rise late this morning through the afternoon. Freezing rain/freezing drizzle just expected across Orange County with not much expected elsewhere with plain rain or plain drizzle being the precipitation mode. Other interior locations may have some isolated locations experiencing sub-freezing conditions with therefore some isolated freezing rain or drizzle, not enough to include in a freezing rain advisory. Questionable forecast data seen in Bufkit NAM and GFS about this afternoon into tonight with temperatures near 2kft as they show them cooling off by a few degrees to below freezing. The RAP and HRRR show the cooling too but keep temperatures near 2kft above freezing. Too much uncertainty and without much dynamic cooling or efficient wet bulb cooling expected, kept plain rain late today through tonight. With moisture laden boundary layer, also put in patchy fog for tonight into early Wednesday.
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&& .SHORT TERM /WEDNESDAY/... For Wednesday, took a blend of MAV/MET/ECS for temperatures. Light rain continues behind the low as 500mb vort max passes south of the region with associated PVA. This will become more of a shower mode by afternoon, mainly across eastern sections. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Active jet stream pattern will continue into early next week. The latest global models and ensemble means are in overall good agreement with just some timing differences. Above normal temperatures will be the theme with NYC likely not falling below freezing through at least early next week. Offshore low will gradually move further east over the Atlantic Wednesday night into Thursday. High pressure settles over the region Thursday into Friday as ridging builds aloft. High temperatures both days will be in the middle and upper 40s for most locations and near 50 degrees in the NYC and NE NJ metro. Active southern branch of the jet will bring the approach of the next system on Friday. And upper low over the Plains will open up on Friday and energy will get driven under building ridging over the eastern States. Models and ensembles have come into better agreement with this system weakening as it approaches Friday night. The weak surface reflection should largely stay to the south of the Tri- State, with potential for some precipitation to graze the region. Confidence is low in the coverage of precipitation since the system is weakening as it moves nearby and lift and moisture are limited. 850 mb 0C line on the GFS, GEFS mean, ECMWF, and ECMWF EPS mean lies across northern New England so snow is not a concern. Inland surface temperatures would be the only concern if precipitation were to make it that far north, and at this time thinking it should be above freezing everywhere for just plain rain. Anomalous ridging aloft continues this weekend and surface high pressure will build down from SE Canada. The active southern branch of the jet will continue as the next system organizes across the central States on Sunday. Global models and ensembles continue to show a strong cut-off low lifting towards the Ohio Valley Sunday night into Monday. Its associated frontal system will gradually approach early next week. Confidence in specific details is low at this point since this is about a week out, but the signals are there for a significant rainfall event. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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A warm front slowly approaches from the southwest through early this evening as low pressure moves through the eastern Great Lakes region. Another low will develop on a triple point across central New Jersey this evening and track south of Long Island tonight. VFR through this morning. MVFR conditions develop around 17Z with light rain. Conditions lower to IFR late this afternoon into early this evening. IFR conditions then remain through 12Z Wednesday with light rain and fog. Winds will be SW to W less than 10 KT to light and variable early then becoming SE this afternoon and then e late this afternoon into this evening. Winds will mainly be 5 to 8 KT. There is uncertainty to the timing and direction of the winds and will be dependent on the movement of the warm front and timing and placement of the developing low this evening. ...NY Metro Enhanced Aviation Weather Support... Detailed information...including hourly TAF wind component fcsts can be found at: http://www.weather.gov/zny/n90 KJFK TAF Comments: Amendments possible as MVFR ceilings could develop before 17Z and visibilities may remain MVFR. Winds may also become SE before 17Z. KLGA TAF Comments: Amendments possible as MVFR ceilings could develop before 17Z and visibilities may remain MVFR. Winds may also become SE before 17Z. KEWR TAF Comments: Amendments possible as uncertainty with the timing of MVFR ceilings developing this afternoon. May be +/- 1-2 hours of 17Z. The afternoon KEWR haze potential forecast is green...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Amendments possible as uncertainty with the timing of MVFR ceilings developing this afternoon. May be +/- 1- 2hours of 17Z. KHPN TAF Comments: Amendments possible as MVFR ceilings could develop before 17Z and visibilities may remain MVFR. Winds may also become SE before 17Z. KISP TAF Comments: Uncertainty with the timing of MVFR ceilings this afternoon and may be sooner than 17Z, and developing IFR conditions may be before 21Z. .OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY... .Wednesday...IFR early, improving to MVFR, in rain and fog. Rain ending in the afternoon with visibilities improving, ceilings MVFR. .Wednesday night...Becoming VFR. .Thursday-Friday...VFR. .Friday night-Saturday...Chance of MVFR or lower with light rain developing.
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&& .MARINE...
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Conditions remain mostly below SCA on the waters with the pressure gradient remaining weak enough today through early Wednesday. The only exception would behind a low Wednesday afternoon, in which ocean waters east of Moriches Inlet could potentially reach SCA criteria. Winds on the ocean will gradually diminish Wednesday night, but some SCA gusts are still possible east of Moriches inlet. Easterly swells from offshore low could bring ocean seas to SCA levels Wednesday night into Thursday. Winds and seas on all waters are forecast to be below SCA levels Thursday night into the weekend.
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&& .HYDROLOGY... No hydrologic impacts are anticipated with around a half inch of precipitation Tuesday through Wednesday morning. Potential exists for a significant precipitation event early next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Freezing Rain Advisory until 10 AM EST this morning for NYZ067. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/DS NEAR TERM...JM SHORT TERM...JM LONG TERM...DS AVIATION...MET MARINE...JM/DS HYDROLOGY...JM/DS

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