Area Forecast Discussion
Issued by NWS Upton, NY

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328 FXUS61 KOKX 260759 AFDOKX Area Forecast Discussion National Weather Service New York NY 359 AM EDT Mon Jun 26 2017 .SYNOPSIS...
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A cold front moves across today with another one following it for Tuesday into Tuesday night. High pressure builds to the south Wednesday. A warm front crosses the region late Thursday, with warm, humid and unsettled weather Friday through the weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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On the large scale, a longwave trough remains west of the region today. A subtle shortwave embedded within this longwave trough with some slight height falls mid to late this afternoon. This in combination with daytime instability allows for a low potential for a shower or thunderstorm. This will be confined to mainly north and west of NYC. At the surface, a cold front will be moving across the region and weakening. Today`s highs were a combination of GMOS and ECS, mid 70s to low 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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The front will become weaker with time. Instability will become more elevated but a lack of a trigger will keep mainly dry conditions tonight. Lows tonight were a blend of GMOS and MAV, low 50s to low 60s. For Tuesday, starting in the morning, there will be abundant clouds. The height falls will be accompanied by greater value of positive vorticity advection during the day. The longwave trough still is west of the region tonight into Tuesday but on Tuesday the amplitude of this shortwave is higher. There wavelength of the shortwave is getting less, indicating a sharper overall large scale trough. The chances for showers and thunderstorms will be higher than those of the previous day. Another cold front moves across Tuesday. Temperatures were a combination of GMOS and ECS, mid 70s to near 80.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Upper trough passes Tuesday evening, with weak ridge building Wednesday. Upper flow flattens late in the week, becoming SW ahead of midwest trough over the weekend. At the sfc, high pressure builds Tuesday night, passing to the south Wednesday. Low pressure passes across the Great Lakes region Thursday, with warm front passing across the area by that time. Thereafter, frontal boundary remains just to the north of the area as low pressure rides along it, also passing north. Then next low approaches ahead of upstream trough, passing north for the latter portion of the weekend. Subtle placement/timing differences noted in medium range guidance. In general, unsettled weather looks likely from late Thursday, through the weekend. Scattered showers and thunderstorms can be expected, with coverage higher during the daytime each day. Instability appears to be weak Thursday, but builds thereafter per operational GFS. LI`s as low as -5 C with long narrow CAPE`s and increasing PWAT`s, over 2 inches by Saturday, in a unidirectional flow supports potential for Flash Flooding - mainly in urban areas. Low humidity and below normal temperatures expected Wednesday, then temperatures rebound to near normal Thursday, and above normal late in the week into the weekend. However, do not foresee heat issues at this time.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR through the TAF period with high pressure south of the region. Winds will continue to become WNW-NW overnight. A brief period of winds 10-15 kt with a few gusts around 20 kt remain possible, but these should quickly diminish in the next hour or so with winds becoming 10 kt or less thereafter. Winds gradually back to the SW on Monday. Afternoon sea breeze development backs winds to the south at coastal terminals, 10 to 15 kt. There is a lower probability of a sea breeze at KEWR and KTEB with winds more likely staying SW-SSW. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Monday night...VFR. Slight chance of an eve shower NW of NYC metros. .Tuesday...Mainly VFR. Chance of a late day shower/tstm. .Wednesday...VFR. .Thursday...Mainly VFR. Chance of a late day shower/tstm mainly north of the NYC metros and Long Island. .Friday...Mainly VFR. Chance of a late day shower/tstm. && .MARINE...
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With an overall weak pressure gradient remaining across the region, winds and seas are expected to remain below small craft advisory criteria (25kt winds, 5 ft seas) through Tuesday. High pressure builds Tuesday night and passes south Wednesday. Sub SCA conditions expected during this mid week period. Then, winds back around to the S/SW as the high departs to the east and a warm front passes. Winds increase, and SCA conditions are possible later Thursday, and Thursday night. These persistent winds continue Friday. Seas build Thursday and remain elevated Friday.
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&& .HYDROLOGY...
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No hydrologic impacts expected through Thursday. There is potential for localized flash flooding associated with summer convection Friday through the weekend - mainly in urban areas. River flooding is not anticipated.
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&& .TIDES/COASTAL FLOODING... Astronomical tides are still running high with potentially another round of isolated minor coastal flooding for the south shore back bays, which could be seen with the high tides tonight (approximately between 10pm and 12am). The water levels would only be expected to touch the minor benchmarks, again for just a few gages in the south shore bays. && .EQUIPMENT... Observations from KFRG (Farmingdale, NY) are not available. Observations from KHPN (White Plains NY) and KHVN (New Haven CT) are being disseminated through backup methods. All is due to an FAA communication line outage. Return to service time is unknown. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...JM/PW NEAR TERM...JM SHORT TERM...JM LONG TERM...PW AVIATION...DS MARINE...JM/PW HYDROLOGY...JM/PW TIDES/COASTAL FLOODING...JM EQUIPMENT...

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