Area Forecast Discussion
Issued by NWS Upton, NY

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702 FXUS61 KOKX 230829 AFDOKX Area Forecast Discussion National Weather Service New York NY 429 AM EDT Sun Apr 23 2017 .SYNOPSIS...
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High pressure builds over the northeast today and moves offshore of southern New England tonight and Monday. A wave of low pressure over the southeastern states moves off the southeast coast Monday, then tracks up along the eastern seaboard through midweek. High pressure will build back in for the end of the week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Surface high pressure builds over the northeast and into the mid Atlantic today, and to the coast late in the day. Aloft weak, near zonal, flow remains. Winds will come around to southeast to south with sea breeze enhancement this afternoon. There will be plenty of sun through today however mixing will be limited, up to around 900 MB, and temperatures will peak at near seasonal levels.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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The surface high moves offshore of the southern New England coast tonight into Monday as the weak zonal flow remains aloft. Meanwhile in the southern stream a low closes off over the Tennessee Valley this morning and then moves slowly in the flow. The low emerges from the southeastern coast late tonight into Monday. The northward progression of the low will depend on the strength of the surface high nosing into the coastal plain. With the weakening of the high late Monday the low will then start to move northward. As a result much of the area will remain dry through Monday with slight chances mainly late Monday morning into the afternoon across NYC and Long Island.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Monday night into Tuesday the NAM becomes slower than other guidance in moving the low north, and leaned toward the slightly faster solutions as the northern high continues to weaken and little ridging remains aloft. The system will remain rather weak and then weaken Tuesday night into Wednesday and the upper low moves along a northern stream trough digging into the central states as a mid Atlantic ridge builds. Timing and amplitude differences become more apparent in the H5 pattern at the end of the week and into next weekend. Winds will increase and become gusty Mon night and Tue. 30-40 kt LLJ lifts through Tue aftn/eve...but a low level inversion should keep most of these winds aloft. These stronger winds will also depend on where the low tracks. If the low tracks over NYC the higher winds will remain to the east. The forward progression of the system is also uncertain...and current forecast may be too quick decreasing pops to chc Wed morning. System departs Wed night with ridging aloft developing over the east and a broad trough out west. This will lead to warming temps through the remainder of the week. A cold front moves towards the area on Thu...but most guidance has showers/tstms mostly dissipating before it reaches the region. This front is then forecast to stall near the area into next weekend with potential waves of low pressure keeping it unsettled. As for temperatures, near seasonable levels through mid week, if not a bit cooler during the daytime due to cloud cover and rain. A significant warmup is possible for the end of the week with rising heights aloft.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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VFR as high pressure builds from the west this morning and passes east this afternoon. NNW-N winds prevail early this morning, generally 10 kt or less. Winds become light N-NE after day break and then turn to the S-SE in the afternoon under 10 kt. .OUTLOOK FOR 06z MONDAY THROUGH THURSDAY... .Sunday night...VFR. .Monday...VFR during the day. Chance MVFR in rain at night. .Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast possible during the day. .Wednesday...MVFR possible early, becoming VFR. .Thursday...VFR.
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&& .MARINE...
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A long period east to southeast swell remains on the ocean waters this morning, with slowly subsiding heights. However, at time seas may approach 5 feet this morning. Otherwise with high pressure building over the forecast waters today winds and seas will remain below small craft levels. The high will move offshore tonight into Monday. A low pressure system will move off the southeastern coast Monday, then track slowly northward along the coast into Wednesday, and then weaken. With an increased surface pressure gradient expected Monday night into Tuesday night, easterly winds will increase, and become gusty. Small craft gusts will become likely late Monday night into Tuesday night across the forecast waters, with ocean seas building to 5 feet or greater late Monday night into Tuesday night. There will be the potential for gusts to approach gale force on the ocean waters late Monday night into Tuesday and possibly into Tuesday night. However, confidence is low as mixing will be limited over the still cool ocean waters. Will continue to highlight the potential in the HWO, Hazardous Weather Outlook. A small craft advisory will likely be needed for Monday night. Ocean seas will be slow to subside and may remain at small craft levels into Friday.
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&& .HYDROLOGY...
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Between 1/2 and 1 1/2 inches of rainfall is possible late Monday into Wednesday. Amounts will depend on the track of low pressure moving along the eastern seaboard. No hydrologic impacts are anticipated at this time.
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&& .TIDES/COASTAL FLOODING...
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There is the potential for minor coastal flooding, mainly along the Long Island south shore bays, with the Tuesday high tide cycles as a low pressure system moves northward along the eastern seaboard.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MET NEAR TERM...MET SHORT TERM...MET LONG TERM...24/MET AVIATION...DS MARINE...MET HYDROLOGY...MET TIDES/COASTAL FLOODING...MET

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