Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290746 AFDOKX Area Forecast Discussion National Weather Service New York NY 346 AM EDT Sat Apr 29 2017 .SYNOPSIS...
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A weak front moves through the area this evening, with high pressure briefly returning for Sunday. A warm front will then move northward through the area on Monday, followed by a cold front from the west Monday night into early Tuesday morning. Weak high pressure will return for the remainder of Tuesday into Wednesday. A frontal system approaches from the southwest Thursday and moves along the coast through late week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A south-southwest low level jet has allowed for the development of elevated thunderstorms along a frontal boundary that will slowly sag southward through the day. The low-level flow will become more westward this morning, allowing any lingering showers and thunderstorms to quickly move eastward through the area, largely ending by mid to late morning from west to east. Calm winds may aid in localized patchy fog in areas outside of any precipitation, though with a shallow inversion expect any fog to dissipate quickly after sunrise. By afternoon, a few gusty winds will be possible, along with a steady increase in mid-upper level clouds. West downslope flow with little marine influence will aid in well above normal temperatures ranging from the 70s to near 80 closer to the coast, and around the mid 80s elsewhere.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
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A few showers and thunderstorms may approach portions of southeastern NY and northern NJ late in the evening, but otherwise dry conditions are expected. As the cold front gradually moves south of the area, flow will turn more north- northeasterly leading to a low-level inversion and the potential for more cloud development keeping low temperatures slightly above climatological normals. The upper ridge centered off the southeast coast will build northward through the Sunday, and in combination with the onshore flow should act to strengthen the low-level inversion. A general lack of overall forcing for ascent along with the inversion should limit precipitation/thunderstorm chances, though if low-level cloud cover thickens sooner than forecast some light drizzle will be possible. Daytime temperatures will be cooler than Saturday, with highs closer to climatological normals.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Onshore flow will continue into Monday morning, with increasing chances of light rain and/or drizzle with a developing stratus deck. By afternoon, a warm front will move through the area with skies briefly clearing from south to north ahead of an approaching cold front. The front moves through Monday night with rain and a chance of thunderstorms giving way to clearing skies, gusty west winds and seasonable temperatures by Tuesday afternoon. The gusty west flow and cooler temperatures will continue into Wednesday as a secondary trough of low pressure moves through. By Thursday, divergence aloft associated with an elongated mid-upper low across the central US will aid in the development of an attendant surface low across the Southeast that will gradually move northeastward through Friday. The prolonged period of south-southwest flow will advect moisture into the region, with increasing chances for precipitation through the weekend.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... A weak cold front pushes through the area today, followed by high pressure building down from Southeastern Canada into tonight. Mainly VFR, with two possible exceptions. First, an area of showers with embedded thunderstorms should impact area terminals from W to E from around 7-14Z. There could be a relatively brief period of MVFR conditions with this. The second is an area of IFR or lower stratus/fog - currently to the south/east of Long Island, which could move into KGON/KISP/KJFK for a few hours early this morning. If this moves in, it will exit with the showers/thunderstorms this morning. Light and variable winds/SSE-S winds under 10kt become SW-WSW around 10kt by mid morning. The winds continue to veer to the W-WNW with gusts around 15-20kt by around midday. By late afternoon/early evening the winds become NW 10-15G20-25KT. Wind gusts should abate by around 00z, with wind speeds falling to under 10kt. Winds continue to veer to the N at under 10 kt by around midnight, with interior terminals becoming light and variable. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late tonight-Sunday morning...VFR. .Sunday afternoon-Monday....MVFR or lower possible. SW winds G15-20kt possible Sunday afternoon. LLWS possible Sunday night mainly at southern terminals. .Monday night...IFR or lower conditions, LLWS and scattered thunderstorms are possible. .Tuesday-Wednesday...VFR. SW-WSW winds G15-20KT possible Tuesday. W-NW winds G20-25KT possible Wednesday. && .MARINE...
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A light to moderate pressure gradient over the region through Monday will limit winds to 15 kt or less, with gusts of 20 kt or less. One of those periods of 15G20KT winds this afternoon and evening will bring seas on the coastal ocean waters east of Fire Island inlet to around 5 ft (mainly 10 or more miles from shore). There for have issued an SCA for Hazardous Seas for the coastal ocean waters east of Fire Island Inlet from noon today through midnight tonight. The pressure gradient tightens Monday night, with 25-30kt gusts possible. These winds will build ocean seas to 4-8 ft Monday night. However, even with 40-50kt of winds at 950 hPa Monday night/early Tuesday morning, will have to strong of a marine inversion for much if any of that to mix down, so gales are not expected then. Winds should be 15 kt or less Tuesday and Wednesday, with a light to moderate pressure gradient over the waters. However, seas on the coastal ocean waters should be slow to come down, and could remain at or above 5 ft into Wednesday, especially over the southern portions of the coastal ocean zones.
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&& .HYDROLOGY...
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No hydrologic impacts are expected through Thursday. A low pressure system approaching from the southwest may lead to periods of heavy rain and the potential for hydrologic impacts late next week into the weekend.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory for hazardous seas from noon today to midnight EDT tonight for ANZ350-353.
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&& $$ SYNOPSIS...MD NEAR TERM...MD SHORT TERM...MD LONG TERM...MD AVIATION...Maloit MARINE...Maloit HYDROLOGY...MD

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