Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 262018 AFDOKX Area Forecast Discussion National Weather Service New York NY 418 PM EDT Mon Sep 26 2016 .SYNOPSIS...
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High pressure moves farther out into the Atlantic as a frontal system approaches from the west this afternoon into this evening. This moves across Tuesday morning but its associated cold front will become stationary and linger not too far off the coast for the rest of Tuesday through Wednesday. Then low pressure over the Ohio Valley and Mid Atlantic states will move slowly up the coast from late Wednesday night through Saturday night, bringing an extended period of unsettled weather. The low will gradually move clear of the area early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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The upper level ridge moves east of the region out into the Atlantic, making the way for an approaching large upper level cutoff low tonight. The associated upper level jet moves into the region tonight, with the right rear quad of enhanced lift moving in by Tuesday Morning. At the surface, a frontal system will be approaching from the west this evening. The warm front will move across late this evening to the beginning of the overnight period. This will be followed by the cold front, which will approach for the rest of the overnight from the west. Expect increasing chances for rain showers overnight into daybreak Tuesday along with increasing winds with developing low level jet. A few gusts up to 30 mph could very well occur especially with mixing down of momentum via the rain showers. Used warmer blend of NAM12/GMOS tonight with abundant clouds, increasing south to southwest winds and incoming rain showers to keep less differences spatially between lows.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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The upper level low remains nearly stationary Tuesday and Tuesday Night. The associated jet remains across the Northeast with the local region staying in the right rear quadrant where lift will be enhanced. At the surface, the cold front will move across from west to east Tuesday morning. However, it appears to slow down on its trek through the region, lingering out east during the day and then slowly moving offshore. The front will be weakening at the same time. The front looks to remain stationary offshore from the model guidance and with approaching weak low along it, may bring a return of rain showers for Tuesday night. Rain showers continue across the region early and then will be slow to diminish across the coast. Favorable setup for synoptic lift is evident within the models so do not totally trust model QPF fields verbatim. A chance of rain showers will remain along the coastline going into the afternoon and the evening. Went with middle of guidance using a combination of GMOS and ECS for max temperatures Tuesday. For min temperatures Tuesday night, used a combination of MET and ECS.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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There is high confidence in the large scale idea of a cutoff low digging south from the Great Lakes and upper Ohio Valley Wed morning, meandering about the Central Appalachians and Ohio Valley from Thu into Sat night, then slowly weakening and lifting out toward the Great Lakes and interior Northeast Sunday into Monday. This should lead to an extended period of unsettled weather and more much needed rainfall, but details on the timing of any heavier rain are sketchy. GFS may be took quick to kick an offshore frontal wave out to the NE and weak offshore ridging, which would allow heavier rain to arrive late Wed night into Thu. The idea of a slower offshore low helping to reinforce surface ridging/cool air damming on its rear flank over New England and into our area should lead to diminishing PoP or even a dry but cloudy interval Wed afternoon and much of Wed night, with heavier rain off to the west. This setup should also lead to a gusty ENE flow from Wed night into Thu evening. Then as onshore low level flow increases and flow aloft becomes more difluent, one favorable time frame for heavier rain to take place may be Thu night. Another may come Fri night into Sat morning as a mid level shortwave and upper jet streak lift northward along the coast. After these features pass, still expect unsettled wx to continue into Sat night and possibly Sunday, and do not have a completely dry forecast in terms of PoP until Monday as the upper low finally weakens and lifts NE to the Great Lakes and interior Northeast. Temps should be near to slightly below average in this unsettled regime.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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Wind has shifted to N-NW at all NYC terminals. Wind will shift to the NW across eastern areas later this afternoon. A few gusts to 25kt are possible. Winds will then continue to veer around to the N- NE tonight at less than 10 kt at all terminal locations. There is a good chance of a sea breeze developing for KJFK, KISP, KBDR and KGON after 16z on Saturday. 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: No unscheduled amendments are expected. KLGA TAF Comments: No unscheduled amendments are expected. KEWR TAF Comments: No unscheduled amendments are expected. KTEB TAF Comments: No unscheduled amendments are expected. KHPN TAF Comments: No unscheduled amendments are expected. KISP TAF Comments: No unscheduled amendments are expected. .Outlook for 18Z Saturday through Wednesday... .Saturday through Sunday...VFR. .Monday into Monday Night...VFR. Potential cold frontal passage with a few showers and thunderstorms. .Tuesday and Wednesday...VFR.
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&& .MARINE...
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Expecting winds to increase tonight ahead of the frontal system. SCA conditions are expected for all waters after 00Z, lasting until 12Z Tuesday. Then, SCA conditions will be more probable across the ocean. The ocean seas are also expected to build to 5-6 ft late tonight into early Tuesday, but SWAN guidance has been recently overestimating by a foot with ocean seas, so have reduced seas accordingly. SCA conditions should REdevelop on the eastern waters on Wed, then spread westward to all waters Wed night into Thu night via an increasing pressure gradient between high pressure to the north and broad/weak low pressure to the southwest, with ENE flow gusting to 25-30 kt. GFS is alone in advertising a period of possible gales and think this is overdone, but will keep mention of low potential in HWO for sake of continuity. Hazardous ocean seas should linger Fri into Fri night.
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&& .HYDROLOGY...
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Between 1/4 to 3/4 inch of rain expected from midnight into Tuesday morning. No hydrologic impacts are expected at this time other than typical urban ponding. Periods of heavier rain with a slow moving low pressure system pose urban flood issues later this week, with the potential for a couple of inches of rain.
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&& .TIDES/COASTAL FLOODING...
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A persistent moderate easterly flow during mid to late week may combine with increasing astronomical high tides associated with the new moon on Friday to cause minor to locally moderate coastal flooding late this week.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT Tuesday for ANZ330-335-338-340-345. Small Craft Advisory from 8 PM this evening to 8 PM EDT Tuesday for ANZ353. Small Craft Advisory from 8 PM this evening to noon EDT Tuesday for ANZ355. Small Craft Advisory from 8 PM this evening to 10 PM EDT Tuesday for ANZ350.
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&& $$ SYNOPSIS...Goodman/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...Goodman AVIATION...IRD MARINE...Goodman/JM HYDROLOGY...Goodman/JM TIDES/COASTAL FLOODING...Goodman

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