Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241848 AFDOKX Area Forecast Discussion National Weather Service New York NY 248 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. This lifts north as a warm front later in the day Thursday. High pressure remains situated over the western Atlantic through the first half of the weekend. A backdoor cold front moves through on late Saturday night into Sunday.
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&& .NEAR TERM /UNTIL 8 PM THIS EVENING/...
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Higher vorticity advection associated with residual cold pool aloft with 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 cold pool aloft shift farther east this evening.
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&& .SHORT TERM /8 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
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For tonight, 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. 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 MONDAY/... A weak area of low pressure over the Canadian Maritimes will push a cold front through the area Wednesday night. This front will then head quickly back north as a warm front, moving through Thursday afternoon. Thereafter, there will be a prolonged period of southerly flow as surface high pressure settles over the Western Atlantic. At the same time, ridging aloft will mean rising heights and therefore, warming temperatures, mainly for areas away from the coast. Closer to the coast, flow off the cooler ocean waters will keep these areas a few degrees cooler than inland. With a southerly flow, dewpoints will also be on the rise. By the weekend, dewpoints could be in the lower 60s, making it slightly uncomfortable for some. The 00Z ECMWF and the 00Z GFS are in better agreement on the passage of a back door cold front late Saturday night into Sunday (quicker than previously forecast). Thereafter, the 2 models differ. The GFS continues to nose a strong high pressure from southeastern Canada into the area, while the ECMWF keeps this high off the Atlantic coast, and is weaker. Though the 00Z ECMWF does nose the high pressure farther inland than the previous run. The GFS solution would keep the area dry for the beginning of next week, while the ECMWF would keep it unsettled. Due to the uncertainty, a blend of models seems reasonable. The cold frontal passages Wednesday night looks to come through dry with limited moisture to work with. There may be some showers and thunderstorms with the warm frontal passage on Thursday, mainly inland as the lower temperatures over the coastal areas stabilizes those areas. A thermal trough sets up over inland areas for Friday and Saturday, which will mean diurnal showers and thunderstorms for these areas. Showers and thunderstorms will also be possible with the backdoor cold front passage late Sunday into Sunday night. This will not be a continuous rainfall event from Friday through Sunday night. && .AVIATION /19Z 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 18Z TAFs through this evening, but confidence on timing and coverage is low. 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. Winds and waves should remain below SCA criteria for the long term with light a pressure gradient.
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&& .HYDROLOGY...
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Rainfall amounts of less than 1/4 inch are expected for the rest into early this evening. Locally higher amounts will be possible in thunderstorms. No concerns for hydrology Wednesday through Monday.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/JP NEAR TERM...JM SHORT TERM...JM LONG TERM...JP AVIATION...MPS MARINE...JM/JP HYDROLOGY...JM/JP

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