Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 252002 AFDOKX Area Forecast Discussion National Weather Service New York NY 402 PM EDT Sat Mar 25 2017 .SYNOPSIS... High pressure over New England will gradually slide east through the weekend...keeping a cold front to our south through Sunday...and then returning as a warm front Sunday night into Monday. Another frontal system approaches on Tuesday and moves across Tuesday night into Wednesday. High pressure returns Thursday ahead of the next front on Friday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Northern stream trough moves east of the Canadian Maritimes tonight...with shortwave ridging building towards the region. Spotty light rain shower or sprinkle activity along the coastal plain should slowly sink south through the late afternoon/early eve. Upper jet streak induced shower activity across central NY/New England late this afternoon will approach northern portions of the Tri- State late today into early this evening. It is likely to weaken as jet forcing moves east...with scattered showers and sprinkles early tonight. Low level cold air damming...under a mild w/sw flow aloft...should strengthen a low-level inversion over the area. This will be a favorable set up for stratus tonight...but low-levels appear too dry for any fog or drizzle under a ne flow. Spotty shower activity may develop late tonight into Sunday morning across W/SW zones as mid- level flow turns southerly with zone of theta-e advection. There is a low probability for spotty freezing rain across far interior zones late tonight/early Sun Morning...particularly Hudson and CT river valleys...due to cold air drainage. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... Models in good agreement with Central Plains closed low lifting into the Mid Mississippi river valley tonight into Sunday...with shortwave upper ridging moving across the area. At the surface...New England high pressure gradually shifts to the coast by late in the day. A swath of scattered shower activity possible to work north across the region during the day Sunday coincident with an elevated warm front and corresponding zone of theta e advection. Any shower activity should be light due to the weak forcing. Increasing potential for shower activity late Sunday into Sunday Evening from sw to ne...as lead shortwave energy approaches around the closed low to the west and moisture increases in deepening sw flow. Warm front will slowly approach from the south Sunday night...supporting drizzle and fog in addition to any shower activity. Closed low opens up and crosses to the north on Monday...with warm front likely struggling to lift north of the area as low pressure tracks ne through Southern Ontario. The warm front could stall over the area with potential for a weak low pressure wave moving along it. The exact location of the warm front/surface low will determine where the heaviest rain axis will occur on Monday...but a wet day expected. There are some hints of weak elevated instability across NW zones...so cant rule out an embedded tstm on Monday in this area as shortwave energy pivots through. Rain should taper off from w to e late Monday into Monday Evening as weak low moves off to the east. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... A weak cold front washes out as it shifts into the region from the NW during Monday night. Probably no showers in association with this feature as lift weakens, however during the evening there could be some lingering showers primarily over eastern sections in association with an exiting shortwave. Clouds will keep overnight lows above normal. Models are split regarding the strength and track of a low pressure wave that could bring the forecast area some rain on Tuesday, primarily in the afternoon. A cold front would then pass through late at night with the chance of more rain. PoPs are capped at chance for now. High temps on Tuesday will be above normal, and if more sunshine occurs than currently forecast, some inland locations west of the city could reach 70 degrees. Wednesday and Thursday look to be dry with high pressure building in. Cold air advection appears to be delayed enough to the point where highs on Wednesday end up above normal, then near-normal for Thursday. Friday could be completely dry as well, but perhaps some rainfall sneaks into the western zones by the end of the day. High temps again near normal. Global models then disagree with the track of an area of low pressure that could bring rainfall on Saturday. Have capped PoPs at 40% for now. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... A cold front will become stationary to the south tonight. High pressure will build in tonight, then weaken on Sunday as a warm front approaches. Bands of light rain or sprinkles passing by this afternoon not having any impact on flight category. MVFR cigs to the north have however already reached KSWF, and should spread southward late today into this evening. A brief period of IFR cigs possible at KHPN this evening. After that, cigs should gradually improve to VFR from NE-SW after midnight, as drier air with the building high to the north moves in. Flight cat Sunday morning uncertain. Started off VFR, then lowered to MVFR after about 13Z-14Z with light rain moving in well in advance of the warm front. Winds have turned mostly N-NE around 10 kt, but sea breeze along the south shore of Long Island could cause winds at KJFK to become more easterly for a couple of hours toward evening. Speeds should pick up a little late tonight, then direction become more easterly after daybreak Sunday, with a few gusts G15-18KT possible at the coastal/NYC metro terminals. .OUTLOOK FOR 18Z SUNDAY THROUGH WEDNESDAY... .Sunday...MVFR with light rain, possibly becoming IFR toward evening. .Sunday night...Lowering to IFR/LIFR with light rain/drizzle/fog ahead of an approaching warm front. .Monday...IFR/LIFR to start. Conds could improve to MVFR or VFR by late morning or afternoon if the warm front moves through. .Monday night-Tue night...IFR likely, LIFR possible with low clouds/fog. .Wednesday...VFR. NW winds G20-25KT, possibly stronger. .Thursday...VFR. && .MARINE... Ocean seas east of Fire Island Inlet will continue to run 4 to 5 feet due to a southerly swell into this evening. Northeast flow strengthens overnight through Sunday between high pressure to the north and the cold front to the south/low pressure to the west. Marginal SCA gusts are possible on the ocean waters late tonight and becoming on Sunday into Sunday Night. The resultant easterly fetch should allow for ocean seas to build to 4 to 7 ft Sunday into Sunday night. Winds are expected to weaken and veer se on Monday as a warm front works into the waters...but e/se swells will likely keep seas at SCA levels. Ocean seas may still be up to 5 ft Monday night due to a lingering swell. Otherwise, sub-sca conditions are expected across all waters through at least Wednesday, however there is a chance that the swell could still linger and bring seas to 5 ft on the ocean waters at times during this period. Winds then increase and become more gusty by Wednesday night with chance of 25 kt gusts mainly on the ocean into Thursday. && .HYDROLOGY... Measurable rain chances gradually increase late Sunday through Monday, with around a half inch to an inch accumulation overall. No hydrologic concerns are anticipated with any periods of rain that occur within the forecast period. && .TIDES/COASTAL FLOODING... A persistent easterly flow may bring water levels close to minor thresholds across the most vulnerable Western Great South bay and Western LI Sound locales for the Sunday Night and Monday Morning high tide. As astronomical tides rise through the week...water levels may flirt with minor levels in the most vulnerable spots during high tides. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 2 AM Sunday to 8 AM EDT Monday for ANZ350-353-355. Small Craft Advisory for hazardous seas until 2 AM EDT Sunday for ANZ350-353. && $$ SYNOPSIS...JC/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...JC AVIATION...Goodman MARINE...JC/NV HYDROLOGY...JC/NV TIDES/COASTAL FLOODING...nv

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