Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 240817 AFDOKX Area Forecast Discussion National Weather Service New York NY 417 AM EDT TUE MAY 24 2016 .SYNOPSIS...
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Low pressure south of Cape Cod tracks northeast today and tonight, moving along the New England coast. High pressure builds in briefly for late tonight and Wednesday. A cold front moves through late Wednesday night into Thursday morning and 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 6 PM THIS EVENING/...
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A weakening low south of Cape Cod tracks slowly northeast through today. A weak surface trough extends back from the low into the lower Hudson Valley. Meanwhile an upper closed, and nearly cutoff low, east southeast of the DELMARVA, as seen on the water vapor loop, drifts north to northeast and begins to fill and get picked up by the northern stream. With areas of energy rotating around the low and the surface low, showers will continue through today. With weak surface and mixed layer instability along with a cold pool associated with the upper low, isolated thunderstorms will be possible. Have kept a mention through the day, however, believe the best chances will be this morning through 18Z. Afterward low level warm advection sets up and caps the area lessening threat of thunder. Some weak elevated cape is available in the afternoon.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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Tonight the upper low continues to fill and becomes an open wave after 06Z and the northern stream carrys the low into Maine and Nova Scotia, merging with low pressure over eastern Canada. The surface low becomes nearly indistinguishable by late tonight, also merging with a surface low over eastern Canada. By 00Z precipitation is quickly ending as heights rise from as weak upper ridging builds to the west. This ridge builds through Wednesday with dry weather late this evening through Wednesday. Warmer air continues to move into the region tonight through Wednesday at the lower and mid levels. A dramatic warmup is expected across the entire region as a westerly flow allows even coastal areas to warm to well above seasonal normals.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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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.
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&& .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Low pressure moves north toward Cape Cod this afternoon. Primarily MVFR through this morning. Some IFR possible as well, primarily east of the city terminals. Improvement to VFR expected this afternoon. Rain will be steadiest through mid-morning, then more scattered thereafter. Isolated thunder possible at any time today, but timing and location not certain enough for inclusion in TAFs. Low confidence with wind direction, however speeds should at least remain below 10 kt. .OUTLOOK FOR 06Z Wednesday through Saturday... .Tuesday night-Thursday...VFR. .Thursday night...Low chance of MVFR in showers. .Friday-Saturday...MVFR possible in afternoon/evening tstms. && .MARINE...
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A weak pressure gradient force will be across the waters today through Wednesday as a weakening low south of Cape Cod tracks to the northeast through tonight and high pressure builds in late tonight and Wednesday. The only hazard across the forecast waters will be isolated thunderstorms today into early this evening. 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 1/3 to 3/4 of an inch are possible today into this evening with the highest amounts across western Long Island, southwestern Connecticut, and Northeastern New Jersey. Locally higher amounts will be possible in isolated 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...JP/MET NEAR TERM...MET SHORT TERM...MET LONG TERM...JP AVIATION...JC MARINE...JP/MET HYDROLOGY...JP/MET

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