Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 242011 AFDOKX Area Forecast Discussion National Weather Service New York NY 411 PM EDT TUE MAY 24 2016 .SYNOPSIS...
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Low pressure south of Cape Cod tracks northeast through tonight, moving into the Gulf of Maine. An associated weak surface trough will move east of the region tonight. High pressure builds in from the southwest briefly for late tonight and Wednesday. This weakens and moves farther offshore Wednesday Night as a weakening cold front moves through by early Thursday. High pressure will dominate through Saturday night as a series of weak upper level disturbances move across. A back door cold front will move through on Sunday. High pressure will build in its wake across New England Sunday afternoon and night, then pass offshore Monday, allowing a broad area of low pressure to begin approaching from the south later Monday into Tuesday.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Through early this evening, higher vorticity advection associated with residual cold pool aloft keeps and the lingering upper level low combined with increased daytime heating has led to scattered showers and thunderstorms. Some gusty winds and small hail as well as heavy rain are possible for brief periods of time with these thunderstorms. Most of the convection has been confined to Southwest Connecticut and Western Long Island Sound. With CAPE values forecast of a few hundred J/KG more showers and thunderstorms will be possible with coverage being scattered. This will decrease with loss of diurnal heating and as the cold pool aloft shifts farther east this evening. For later this evening and through the overnight, the region will be behind a weak surface trough. The upper level low and associated cold pool aloft shift east of the region. This will increase subsidence with ridging aloft. The lows were a blend of 1/3 MET, 1/3 MAV and 1/3 12z GMOS. 850mb temperatures increase through the night. A light westerly flow is conveyed by the models which will help mix down some relatively warmer air tonight despite the decrease in clouds, thereby mitigating radiational cooling. With lighter winds across the interior, min temperatures were further lowered by a degree. Also with lighter winds across the interior and residual low level moisture...there could be some patchy fog late into early Wednesday Morning.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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For Wednesday, the surface trough will be just east of the region. This will allow for westerly flow to continue. Aloft...ridging continues with high pressure establishing itself southwest of the region. A very warm day is expected with highs around 15 degrees above normal on average...cooler at the immediate eastern shorelines with partial sea breeze influences. Overall though less marine influence with the more westerly flow. For Wednesday Night, aloft there will be continued ridging. At the surface, the pressure gradient will become weak with high pressure becoming weaker and translating farther south into the open Atlantic. A parent low moves into the Canadian Maritimes but will be filling in with increasing central pressure...essentially weakening. The associated cold front moves through by early Thursday but will be weakening as well.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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Summerlike warmth will continue through the first half of the weekend as longwave upper ridging moves across. Shortwave disturbances will however be able to move through the longwave ridge and bring chances for late day convection mainly from NYC north/west both Friday and Saturday. GFS seems too quick to do so on Thursday as well, and think any convection that day will be isolated in nature and confined to well NW of NYC. High temperatures both Thu/Fri will be well into the 80s in most places, and some isolated lower 90s are not out of the question somewhere in urban NE NJ, in the valleys of Orange County, or the interior lower CT river valley. Lows will range mostly from the mid 50s to the mid 60s. The ridge then weakens across New England in response to a sharp northern stream disturbance moving across eastern Canada, pushing a back door cold front through on Sunday as a surface high builds across New England. Forecast details become less certain from Sunday onward, and will be dependent on how far south the front sinks. Forecast temperatures could be at least several degrees cooler and chances for rain lower if the front does push farther south. Leaning more toward the ECMWF idea of more of a glancing blow from this cooler air mass for now. As we go into Monday night and Tuesday, we should start dealing with influx of Atlantic moisture well north of a subtropical or tropical weather system now just beginning to organize near and northeast of the Bahamas, and forecast by global models to head toward the Southeast coast.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/...
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Isolated to scattered SHRA/TSRA will pass through the terminals through this evening. Will carry VCSH/VCTS in the TAFs through this evening. TSRA will not every terminal. Most storms will miss most terminals. Generally a VFR forecast. Conds may briefly lower to MVFR in SHRA/TSRA. In addition, MVFR VSBY possible in areas of BR late tonight, mainly away from KNYC terminals. Winds generally ranging from N to NW at 5-10 KT. Winds become LGT/VRB this evening and tonight. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90. KJFK TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. Low confidence on sea breeze development. KLGA TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. Low confidence on sea breeze development. KEWR TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. KTEB TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. KHPN TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. Low confidence on sea breeze development. KISP TAF Comments: Occasional SHRA/TSRA possible through this evening with brief MVFR conds. Low confidence on sea breeze development. .OUTLOOK FOR 18Z Wednesday through Sunday... .Wednesday through Thursday...VFR. .Thursday night through Friday morning...Occasional MVFR in showers/thunderstorms possible. .Friday-Saturday...MVFR possible in afternoon/evening tstms. .Sunday...VFR.
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&& .MARINE...
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A weak pressure gradient force will be across the waters through Wednesday Night, allowing for forecast winds and seas to stay below SCA criteria. The only hazard across the forecast waters, mainly the western forecast waters, will be isolated to scattered thunderstorms this afternoon into early this evening with potential for gusty winds, heavy rain and small hail. Otherwise no hazardous conditions are expected. Minimal SCA conditions mainly in the form of higher ocean seas may be possible Sunday afternoon and night as easterly flow increases following a back door cold frontal passage.
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&& .HYDROLOGY...
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Rainfall amounts of less than 1/4 inch are expected into early this evening. Locally higher amounts will be possible in thunderstorms. Local minor flood impacts from heavier showers/tstms are possible both late day Friday and Saturday, possibly still well inland well N/W of NYC on Sunday.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Goodman/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...Goodman AVIATION...MPS MARINE...Goodman/JM HYDROLOGY...Goodman/JM

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