Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 272329 AFDOKX Area Forecast Discussion National Weather Service New York NY 729 PM EDT Sat May 27 2017 .SYNOPSIS... High pressure will remain fairly stationary to the east of the region through Sunday Night...retreating northeast on Monday. A frontal system will approach the region Sunday Night and cross the area Monday. A series of weak fronts or troughs of low pressure will follow through the end of the week. && .NEAR TERM /THROUGH SUNDAY/...
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Forecast is on track. Isold instability showers still on the scope...although coverage should dissipate this evening in wake of a vorticity center moving through the region. However... can`t rule out an isolated shower lingering across NYC metro and points NW through around midnight with a separate northern stream shortwave/jet streak digging into eastern New England. Otherwise...Weak upper ridging builds into the region overnight...with surface high strengthening to the east of New England. This will have a Canadian maritime airmass taking hold of the region. Combination of low-level onshore flow and nocturnal cooling will likely result in stratus development overnight into Sun morning. Models are signaling potential for some patchy fog and/or drizzle developing late tonight...although confidence is low as saturation doesn`t appear to be sufficient. Temps should remain near seasonable in the 50s.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH 6 PM SUNDAY/... Upper ridge axis moves across the region Sunday...with a deep upper low sinking south into the upper Mississippi River Valley through Sunday Night. Ahead of it southern stream energy/moisture expected to ride into the region Sunday Night...preceding approaching northern stream shortwave energy. Canadian maritime airmass will be entrenched on Sunday...with any morning stratus likely slowly to erode into the afternoon. The stable low-level airmass should keep the region dry on Sunday...with temps running below seasonable in onshore flow and and with cloud cover. Developing diffluent flow aloft...approaching shortwave energies and jet streak...combined with an increasingly moist S/SW flow ahead of an approaching frontal system will result in increasing likelihood for rain late Sunday Night. Model spread exists in timing and intensity of rainfall...which is likely related to model handling of convectively induced vort/shortwave energy originating over the Mid-Mississippi and Tennessee River valleys and riding into the region and associated moisture/instability influx. Should see some better agreement on these details Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... Global models are in decent agreement with the overall H5 pattern through the period. However...there are timing differences from mid week on with regards to pieces of upper level energy moving across the area. Cutoff low pres over southern Ontario will slowly track ewd through the week although maintain it`s hold on the weather pattern across the area. Mid level shortwave trough moves through the area on Mon. The NAM is the strongest with the upper level energy associated with it and thus strongest at the sfc with highest QPF as well. Differences appear to be associated to the convection over the midwest today which is where this system is originating from. Hopefully next 24 hours will converge better. At any rate...Mon looks like a wet day with rain becoming widespread during the morning. Elevated instability present could trigger some tstms. See hydro section for info on totals and impacts. Weak ridging builds in Mon night with rain ending as the shortwave trough exits to the NE. A weakening cold front approaching from the west on Tue could trigger a few showers/tstms during the aftn and into the evening as it moves into the area. Chc showers may linger through the night. The closed upper level low remaining over SE Canada will send rounds of upper level energy through the area through the end of the week. Have maintained schc to low chc pops at times through the period but will need to be fine tuned as the week progresses. Temps will be above normal levels during the daytime with the exception of Monday when they will be near to slightly below normal with clouds and rain. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/...
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Weak high pressure remains over the terminals thru Sunday. VFR to start, however a period of MVFR with stratus will develop overnight between 07Z and 10Z. VFR cigs return mid- morning Sunday. Light SE winds tonight. .OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY... .Sunday night...Late night MVFR with chc shra/IFR. .Monday...MVFR conds likely and IFR conds possible. Showers likely and chance of tstms. .Tuesday-Wednesday...Mainly VFR. Chance of showers/tstms mainly NW of the NYC metro terminals. .Thursday...VFR.
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&& .MARINE... Tranquil through Sunday night as ocean swells gradually subside and winds remain light. SE winds increase to 15-20 kt late Sunday Night into Mon with possible gusts up to 25 kt on the ocean waters...which could lead to seas reaching 5 ft. Otherwise...tranquil conds are expected through the remainder of the forecast period. && .HYDROLOGY...
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Total rainfall amounts on Monday could range from 1/4 to 3/4 inches...with the potential for 1 to 1 1/2 inches if a stronger solution verifies. No significant widespread hydrologic impacts are expected attm through at least the middle of next week.
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&& .TIDES/COASTAL FLOODING... The combination of high astronomical tides and southerly swell will keep water levels within striking distance of minor coastal flood benchmarks for the night time high tide cycles into Monday Night. Widespread minor coastal flooding is expected for the high tide cycle tonight along the south shore bays of Brooklyn/Queens/Nassau, also for the shores of Westchester/Fairfield along western Long Island Sound. A coastal flood advisory continues. Brief and localized minor coastal possible for the remainder of the western LI Sound...lower NY/NJ harbor and SW Suffolk. Tides lower for Sun Night high tide...but surge likely increases a bit with strengthening SE flow. The net result...looks to be potential for additional widespread minor coastal flooding for the southern bays of Western LI...with localized and brief minor flooding for the remainder of areas that have been affected over the last several days. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...Coastal Flood Advisory from midnight tonight to 3 AM EDT Sunday for CTZ009. NY...Coastal Flood Advisory from midnight tonight to 3 AM EDT Sunday for NYZ071. Coastal Flood Advisory until 2 AM EDT Sunday for NYZ075-178- 179. Coastal Flood Advisory from 10 PM Sunday to 3 AM EDT Monday for NYZ179. NJ...None. MARINE...None.
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&& $$

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