Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 230452 AFDOKX Area Forecast Discussion National Weather Service New York NY 1252 AM EDT Sun Jul 23 2017 .SYNOPSIS...
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A frontal boundary remains to our south tonight as a wave of low pressure tracks along it. This front then sags farther to the south later today after the low passes. Another low then moves along the front, tracking off the mid-Atlantic coast by Monday morning. Still another area of low pressure that moves through the region Monday and Monday night, exits to the east Tuesday. High pressure builds over the northeast late Tuesday through Wednesday, then drifts off the coast Wednesday night. Another wave of low pressure follows for Wednesday night into Friday, with a cold front moving through Friday. High pressure returns Saturday.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Forecast remains generally on track. Heavier showers have developed in and around NYC, but this activity is progged to pass east early this morning. Once a mid and upper level shortwave exits, some drying should occur except for possibly some lingering showers mainly over Long Island. Lows tonight should be around 5 degrees above normal.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/... The region should be under locally zonal flow Sunday. With no shortwaves of note forecast to move over the region in this flow, it should be mainly dry. However, this is quite a change from the previous forecast. So to trend things, went with slight chance pops over western zones and mainly dry over eastern zones through late afternoon, then increased pops to chance over far western zones and slight chance throughout elsewhere (reflecting climatological trends for convection). A sharpening 700-500 hPa trough/developing closed low moving into the Great Lakes Sunday night, along with 850 hPa frontogenesis, will produce an increasing threat of showers, with a slight chance of thunderstorms. The pops increase from W to E, to likely throughout by after midnight. Onshore low-level flow should result in a mostly cloudy sky on Sunday, limiting highs to near to slightly below normal levels (mainly around 80-mid 80s). Lows Sunday night should be slightly above normal due to cloud cover. There is a moderate risk for the development of rip currents at ocean beaches Sunday. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... An upper level shortwave and accompanying wave of surface low pressure will be exiting to the east Monday night into early Tuesday. Showers and isolated thunderstorms will be on-going at the beginning of the extended forecast period. Instability and CAPE will be marginal and increase somewhat during Monday, however may still not be sufficient to support widespread convection, so will keep isolated wording. The upper westerly flow will be progressive through the period. A weak ridge builds Monday night into Tuesday, and Wednesday. Then another shortwave, with an embedded closed low, over the Canadian west coast Monday, opens and digs a more significant trough into the eastern states Wednesday night into Thursday with a high amplitude trough, of 1 to 2 standard deviations above normal, digging all the way to northern Florida by Friday. The flow looked to be still progressive with a surface low moving through Thursday and Friday. However, there are hints that the upper low will close off again Friday into Saturday and remain along the northern coast into next weekend. At this time will keep with persistence and the more progressive flow and keep Friday night into Saturday dry as upper ridging builds to the north. Temperatures through the extended period will be near to slightly below seasonal normals. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... A weak cold front will remain nearly stationary just south of the area through tonight. Low pressure will pass just south along this front tonight. Expect mostly VFR conditions through the TAF period. Can not rule out some brief period of MVFR in any heavier showers. Some MVFR cigs have been reported at KJFK. Unsure just how long they last. Will cover in a TEMPO for now and monitor the next hour or so. Have removed all thunder from TAFs tonight. All lightning activity remains south of the area terminals, where the best dynamics remain. So will go with just showers through 07Z-09Z. Drier weather is expected for Sunday. Winds will shift from the south to the northeast tonight, then shift to the southeast on Sunday for most terminals, with speeds generally 10 kt or less. .OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY... .Sunday night-Monday night...Episodes of SHRA/TSRA with MVFR or lower conditions possible. .Tuesday...An AM shower possible at KGON, otherwise VFR. .Tuesday night-Wednesday night...VFR. .Thursday...Sub-VFR possible in SHRA/TSRA && .MARINE... A light to moderate pressure gradient over the waters around Long Island through Sunday night, will limits sustained winds to 15 KT or less, ocean seas to 4 ft or less, and seas/waves on the non- ocean waters to 1 ft or less through then. Winds, gusts, and seas will remain below small craft levels Monday through Thursday. However, ocean seas may approach 5 feet Wednesday night into Thursday as an increasing southerly flow develops ahead of a cold front. Waves of low pressure passing through the waters will bring a chance of thunderstorms Monday and again Thursday into Thursday night. && .HYDROLOGY...
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Currently expecting up to an inch in spots across southern portions of the CWA and less than 1/4 of an inch of rainfall elsewhere through morning. An additional 1/2 to 1 inch of rainfall is likely from Sunday night into Monday night, with locally higher amounts possible. There is a small chance for minor flooding or urban and poor drainage areas, if any experience locally heavy rainfall. More rain is possible late Wednesday night through Friday. Significant hydrologic impacts are not expected at this time.
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&& .TIDES/COASTAL FLOODING... With the approach of the new moon (Sun), tides will run high this weekend into early next week. Positive tidal departures of 1/2 to 1 ft will be needed for minor flooding during the night time high tides during this time. Minor flooding is possible starting with the high tide cycle this evening, mainly in the western south shore bays of Long Island. A bit more widespread minor flooding is possible Sunday night with an E/NE flow expected. The threat for minor flooding could continue into Monday, with E/NE flow progged to continue. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...Maloit/MET NEAR TERM...BC/Maloit/MET/PW SHORT TERM...Maloit LONG TERM...MET AVIATION...BC MARINE...Maloit/MET/PW HYDROLOGY...Maloit/MET TIDES/COASTAL FLOODING...

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