Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 231336 AFDOKX Area Forecast Discussion National Weather Service New York NY 936 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 late today into 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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Region will lie in a near zonal upper flow today between a polar upper low over Hudsons Bay and a closing upper low moving through the deep south. At the surface...high pressure builds into the region this morning and then east this afternoon into tonight. Mostly sunny conditions today with sunshine occasionally filtered by jet cirrus. Light NE flow in the morning expected to give way to afternoon return flow and s/se sea breezes. Early/mid afternoon sea breeze will limit temps along the south coastal areas to the upper 50 to lower 60s...and mid 60s for NYC/NJ metro with mid to late afternoon sea breezes. Temps across the far N & W interior should be able to rise into the upper 60s to around 70 with deeper mixing and outside of maritime influence.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... 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. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... 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. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... VFR as high pressure builds from the west this morning and passes east this afternoon. N-NNE winds this morning will turn to the S-SE early this afternoon. Timing of wind shift may be off by 1-2 hours in TAFs. Speeds will be 10 kt or less. Winds diminish tonight and become light and variable outside of city terminals. .OUTLOOK FOR 12z MONDAY THROUGH THURSDAY... .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. && .MARINE...
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A long period east to southeast swell will slowly subside through the day. 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... 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. && .TIDES/COASTAL FLOODING...
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Potential for minor coastal flooding for vulnerable coastal communities...mainly along the southern bays of Western LI and Western LI Sound...with the Tue eve high tide cycle. This is in response to a low pressure system moving northward along the eastern seaboard. Only 1/2 to 1 ft of surge is needed to reach minor flood thresholds Tue evening.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MET NEAR TERM...NV SHORT TERM...MET LONG TERM...24/MET AVIATION...DS MARINE...24/MET HYDROLOGY...NV TIDES/COASTAL FLOODING...NV

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