Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290843 AFDOKX Area Forecast Discussion National Weather Service New York NY 443 AM EDT SUN MAY 29 2016 .SYNOPSIS... Westward extension of a bermuda high pressure persists through today. The high weakens and moves further into the Atlantic tonight into Monday. A cold front will move across the area Monday night into Tuesday. High pressure returns through the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... With westward extension of Bermuda high pressure over the region and deep upper ridge over the area, feel conditions today will be similar to those observed on Saturday. Have went above guidance with high temperatures away from the immediate coast. Flow initially starts out southwesterly, but will become southerly in the afternoon. This should cap temperatures at the immediate coast in the upper 70s to near 80 degrees, and conditions could even be a bit cooler over the Forks of Long Island and SE CT. Highs from the city north and west will be in the upper 80s and lower 90s. While the flow becomes southerly in the afternoon, locations north and west of the city will warm quickly and should still obtain forecast highs. Moisture will be on the increase as heights fall aloft and the ridge axis moves offshore in the afternoon. The best chance of scattered convection will be across the interior away from sea breezes, so will forecast a low chance pop here tapering to slight chance a bit further east towards the city. There is a moderate risk of rip current development at Atlantic facing beaches today. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
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Main focus this period is on potential heavy rain event late tonight through Monday. Heights continue to fall aloft this evening and southwest flow will be on the increase. Tropical moisture will quickly advect northward as the the flow taps into moisture from Bonnie across the Carolinas. Precipitable water values are progged to be near 2 late tonight into Monday. These values are close to the highest observed for May 30 per SPC Sounding Climatology across the area. This coupled with shortwave energy approaching from the west and the region being located in the right entrance region of an upper jet to the north sets the stage for heavy rainfall. Models continue to show spread on rainfall amounts late tonight through Monday. SREF plumes show several members with rainfall under a half inch and some members approaching 1.5 inches with the mean right around 1 inch. Meanwhile, the GEFS plumes show a clustering between 1 to 1.5 inches of rainfall especially east of the Hudson River. There is a fairly high confidence that bands of heavy rain will develop late tonight across western zones and then move to the east through the day on Monday. There could be training of cells as larger bands of rain move to the east, so locally heavy rainfall is possible. There continues to be potential for minor urban and small stream flooding and it would not be out of the question for localized flash flooding. However, confidence is low on where this may occur so have will not issue a watch at this time. This is in collaboration with all neighboring offices and will continue to mention potential in the HWO. Instability is lacking during this event so will only show a mention for isolated thunder. Rain tapers off from west to east across the area in the afternoon and evening. Cannot rule out a few showers behind the main plume of moisture as a cold front moves across the area so will show slight chance pops overnight. Temperatures on Monday will much cooler than recent days as abundant clouds and precipitation will hold readings in the 70s.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/... Models continue to slowly come into better agreement with the overall 500 hPa pattern across North America, although timing and amplitude differences still become apparent by the middle of the week which is impacting the progression of a cold front late in the week. Approaching shortwave trough flattens as it moves across Tuesday morning. Interestingly, the 00z ECWMF keeps a stronger trough and helps pull more tropical moisture towards southern portions of the region Tuesday morning. This solution appears to be an outlier at time, but will hold onto slight chance pops near Long Island as do not want to completely discount the idea that a few showers develop with the passage of the flattening trough. Cold front moves offshore on Tuesday and ridging begins to build aloft later Tuesday into Tuesday night. This ridge dominates the weather through Thursday with surface high pressure moving across New England Wednesday into Thursday. The 00z ECWMF tries to bring some remnants of Bonnie towards the area on Thursday, but currently feel this is overdone with ridging aloft and subsidence at the surface from high pressure just to our northeast. A cold front approaches on Friday and will slowly move east into Saturday. Not much instability noted in model soundings so will just advertise a chance of showers with the front. Above normal temperatures return on Tuesday and Wednesday before an onshore flow will bring temperatures down to near normal levels for the end of the week. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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The region will remain under the influence of a westward extension of the Bermuda High today. A trough of low pressure builds in Sunday evening. Most likely VFR through at least 21z today. There is quite a bit of uncertainty on whether low clouds (IFR or lower) move in late this afternoon/this evening at Long Island/Coastal CT terminals and KJFK. This could happen as early as 22-23z KGON and 1-2z KJFK/KISP/KBDR. For now time with onset of moderate showers at each terminal...except start at 4z at KGON. Showers should move into area terminals from sw to ne this evening...but probably will not reach KGON by 6z Monday. Conditions deteriorate to MVFR to IFR as the showers move in. SW-S flow develops starting at 13z at under 10 kt and gives way to seabreezes (around 10-15kt) at all but KSWF late this morning/this afternoon. Could see isolated gusts to around 20 kt at coastal terminals...maybe even 25 kt at KJFK. Winds become light and variable throughout this evening. .OUTLOOK FOR 06Z Monday through Thursday... .Late Sunday night-Monday...MVFR or lower likely after midnight. Showers/thunderstorms could produce locally heavy rainfall. .Monday night-Tuesday night...Becoming VFR Monday Night. .Wednesday-Wednesday night...VFR. .Thursday...Low chance of MVFR or lower. E-SE winds g15-20kt possible.
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&& .MARINE... A weak to moderate pressure gradient over the region through Thursday will keep sustained winds to 15 kt or less over the waters around Long Island. There is quite a bit of uncertainty on how much residual swell from Tropical Cyclone Bonnie will impact the coastal ocean waters early next week. As a result, seas to around 5 ft cannot be ruled out mainly in the Monday-Tuesday time frame on the coastal ocean waters. However, the confidence in this occurring is too low to warrant mentioning in the forecast at this time. Outside of this potential, seas should remain below Small Craft levels through Thursday as well. && .HYDROLOGY... No widespread precipitation is expected today. For tonight through Monday Evening...a widespread 1 to 1.5 inches of rain is forecast. Locally higher amounts are also possible. This rain could lead to minor urban and small stream flooding and there is chance for localized flash flooding as well. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...DS NEAR TERM...DS SHORT TERM...DS LONG TERM...DS AVIATION...Maloit MARINE...Maloit HYDROLOGY...DS is the U.S. government's official web portal to all federal, state and local government web resources and services.