Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290808 AFDOKX Area Forecast Discussion National Weather Service New York NY 408 AM EDT FRI JUL 29 2016 .SYNOPSIS... Low pressure approaches from the southwest tonight and passes through the region Friday. The low departs late in the day Friday with high pressure building to the north. Weak high pressure briefly builds into the region for parts of Saturday. Unsettled weather returns Saturday night through Sunday night with the passage of another low pressure system. Drier weather is expected for the first half of next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... The widespread area of heavy showers and thunderstorms have weakened over Orange County, all that remains is some light rain over the Lower Hudson Valley and Northeast New Jersey. An area of light to moderate rain moving into Northwest New Jersey moving northeast should move into the area over the next couple of hours. Since much of the rain is not associated with thunder, took mention of scattered thunderstorms out and went with isolated instead. Otherwise, only minor changes made. A coastal trough remains along with a deepening low over Virginia. This low is associated with the vigorous shortwave moving through the northern trough over the eastern states. A combination of the deepening low and warm frontogenesis through southern NJ to south of Long Island 03z to 06z will bring increasing chances for showers, and with marginal instability thunderstorms. A deep layered southwest flow around sub tropical high pressure off southern coast and into the northern stream trough was transporting tropical moisture into the region. There will be potential for heavy rain developing later this evening and overnight as lift increases with the frontogenesis. A flash flood watch has been posted to this evening and into Friday. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Timing and tracking of the deepening low across the region during Friday is still somewhat uncertain, although there is now more consistency with the low tracking just south of Long Island Friday afternoon. Increasing shear along the warm front late tonight into Friday afternoon will increase the threat of severe storms across metro NYC, Long Island, and into coastal CT, along with continues heavy rainfall. Speed of the low has increased and precipitation is now expected to taper off from the west during the afternoon. Weak ridging builds behind the shortwave late Friday into Friday night with surface high pressure building from the northwest. Friday night will be dry with a cooler airmass moving into the area. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Weak high pressure will remain over the region Saturday morning, resulting in a dry Saturday morning. An approaching shortwave may set off a few scattered showers and thunderstorms Saturday afternoon, mainly west of NYC. East of NYC, conditions appear to remain mostly dry. The unsettled weather becomes more widespread Saturday night into Monday, as the shortwave and its associated low pressure system moves across the region. Expect showers and thunderstorms, through this time frame with some storms producing locally heavy rainfall. High pressure builds back into the region early next week, providing mostly dry conditions. A few isolated showers or thunderstorms cannot be ruled out during the first half of next week...mainly N and W of NYC during the afternoon hours. Temperatures will remain seasonable through the long term with highs each day climbing into the 80s. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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Low pressure along the Mid Atlantic coast will pass to the south today. Associated bands of heavy showers with IFR vsby have already taken shape from just north of NYC into northern NJ, eastern PA, and northern MD. KTEB/KHPN have already experienced IFR and brief LIFR vsby with the heavier activity, and think most of this activity will remain there and at KEWR through about 10Z, then move eastward and impact all of the NYC metro terminals plus KHPN from about 10Z until at least 14Z, and KISP/KBDR from 11Z to at least 15Z. LIFR conditions at KGON attm should improve to IFR as rain arrives there by 12Z and continues until at least 16Z. Occasional rumbles of thunder not entirely out of the question. These showers could last a couple of hours longer than outlined above, then a slow improvement to VFR expected this afternoon. NE winds could gust between 15-20 at the coastal terminals this morning. .OUTLOOK FOR 06Z SATURDAY THROUGH TUESDAY... .Late Fri night into Sat morning...Light fog with MVFR vsby possible...then VFR late Sat morning. .Sat afternoon into Sunday...Chance of showers and possibly a tstm. MVFR or lower conditions possible. .Sunday night-Mon night...Chance of showers. MVFR conditions possible. .Tue...Mainly VFR.
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&& .MARINE... Winds and seas are expected to remain below small craft advisory levels tonight through Friday. A wave of low pressure is forecast to track through or near the waters Friday. Depending on the track of the low briefly higher winds and seas near small craft levels will be possible on the ocean waters east of Moriches Inlet. Showers and thunderstorms will be possible from this evening through Friday. Some of the thunderstorms Friday may produce gusty winds in excess of 35 KTS, especially over the ocean waters. At this time fog formation is not expected. A light pressure gradient over the area waters will result in sub- sca conditions this weekend and early next week. However, any thunderstorms that develop on the waters may produce brief SCA conditions. && .HYDROLOGY... A flash flood watch is in effect for the entire CWA tonight through Friday for the potential of 2 to 4 inches with locally higher amounts. The axis of heaviest rain at this time is expected across northeastern New Jersey into the Lower Hudson Valley and NYC, and into southwestern Connecticut. Uncertainty remains as to where the heaviest rain occurs and depends on the track of low pressure through the region. Also, the speed of the low will affect the timing of precipitation. Another round of showers and thunderstorms can be expected Saturday night through Sunday...with some storms possibly producing heavy rainfall. Exact precipitation amounts are unclear at this time. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Flash Flood Watch through this afternoon for CTZ009>012. NY...Flash Flood Watch through this afternoon for NYZ071>075- 078>081-176>179. NJ...Flash Flood Watch through this afternoon for NJZ004-006- 103>108. MARINE...None.
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&& $$ SYNOPSIS...BC/MET NEAR TERM...JP SHORT TERM...MET LONG TERM...BC AVIATION...Goodman MARINE...BC/JP/MET HYDROLOGY...BC/MET

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