Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 220828 AFDOKX Area Forecast Discussion National Weather Service New York NY 428 AM EDT FRI JUL 22 2016 .SYNOPSIS...
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High pressure builds further offshore today as a cold front approaches and moves through early Saturday. High pressure over the area this weekend moves offshore early in the new week, and then a cold front approaches on Monday and passes through the area Monday night. High pressure returns for Tuesday through Thursday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Mid level shortwave and associated sfc low pass well to the north this morning. A SW flow will increase as the pressure gradient tightens between high pressure off the Mid Atlantic Coast and the aforementioned low. This will pump a hot and more humid airmass into the region today. A heat advsy remains in effect for NYC and most of NE NJ with max heat indices ranging from 95 to 100 degrees this afternoon. Rest of region heat indices into the 90s. A pre-frontal trough will also develop over the area which could be the trigger for showers and tstms this afternoon although coverage is questionable due to the lack of upper level support. Moderate instability will develop...but shear is lacking until the next shortwave approaches this evening and tonight. A few storms that develop late this aftn could become severe as the upper jet/vort move closer...although the disjointed nature of the scenario has resulted in a low confidence forecast for a widespread severe weather event. Models are in good agreement on the timing of the better upper support coming tonight. A high risk for rip current development at ocean beaches will be also be developing this morning...and continuing to be high through the evening due to southerly wind waves increasing to 3 to 5 ft and a residual 2 ft se swell.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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Models are also in good agreement that the best dynamics from the shortwave and jet streak approaching tonight will be closest to eastern CT/LI with areas N of here in the sweet spot. Models are still indicating moderate instability into the overnight hours as a cold front approaches and while severe wx typically doesn`t occur at night here...this could be an exception...especially during the first half of the night. Showers and thunderstorms taper off late tonight with the passage of the cold front early Saturday. Another hot day Saturday but relatively drier with the westerly flow. This should allow for more vertical mixing and lower dewpoints. Although the dewpoints are expected to be lower...temperatures will be higher with heat indices well into the 90s once again. The heat advsy continues for NYC on Sat and may also be needed again in NE NJ with values near 100...but the uncertainty in mixing down lower dewpoint air from the top of the mixed layer could preclude this and keep it just below. Therefore...do not have the confidence to extend NE NJ attm.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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High pressure builds back into the area from the west Saturday night through Sunday. High temps on Sunday will top off in the upper 80s to low 90s for most areas, but will be in the low to mid 90s for NYC, portions of NE NJ, and southern portions of the Lower Hudson Valley. With a W-NW flow, dewpoints should not be as high as Saturday, generally in the upper 50s to low 60s. This results in heat indices below 95 degrees. The high moves offshore Sunday night, and return flow develops on the back side of the high. Dewpoints will creep up into the mid and upper 60s Sunday night through Monday as S flow increases ahead of approaching cold front. Highs on Monday will top off in the low to mid 90s, and heat indices will top off in the mid to upper 90s. As cold front approaches on Monday, scattered showers and thunderstorms will develop over western areas, and those storms will continue to develop and spread east as that front advances and pushes through the region Monday night. With deep S to SW flow, low level moisture will increase throughout the region, and a very warm and humid night on tap with lows near 80 in/around NYC, and in the low to mid 70s elsewhere. Surface dewpoints will will be in the low 70s, resulting in overnight heat indices in the 80s for NYC and urbanized portions of NE NJ. Areas of fog are likely as well. Behind the cold front, surface dewpoints fall back into the 60s. It will take some time for cooler and dryer air to build east. Highs on Tuesday will climb back into the low to mid 90s, and with surface dewpoints in the 60s, heat indices will once again top off in the mid 90s. High pressure continues to build in from the west for the midweek period. Temperatures will top off in the upper 80s to low 90s on Wednesday, and then will top off in the mid to upper 80s on Thursday.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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High pressure remains offshore today. A cold front approaches tonight and moves through early Saturday. Generally VFR conditions expected through the day today, except in any stronger thunderstorm that develops. By late this evening and continuing overnight, patchy fog and MVFR/local IFR vsbys are possible. Southwest winds around 10 KTS expected through early this morning. Speeds increase between 12Z and 16Z to around 15 KTS with gusts in excess of 20 KTS. ...NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http://www.weather.gov/zny/n90 KJFK TAF Comments: Gusts of 25 to 30 kt are possible this afternoon. Amendments for thunderstorms late this afternoon and evening are possible. KLGA TAF Comments: Gusts of 25 to 30 kt are possible this afternoon. Amendments for thunderstorms late this afternoon and evening are possible. KEWR TAF Comments: Gusts of 25 to 30 kt are possible this afternoon. Amendments for thunderstorms late this afternoon and evening are possible. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Gusts of 25 kt are possible this afternoon. Amendments for thunderstorms late this afternoon and evening are possible. KHPN TAF Comments: Gusts of 25 kt are possible this afternoon. Amendments for thunderstorms late this afternoon and evening are possible. KISP TAF Comments: Gusts of 25 to 30 kt are possible this afternoon. Amendments for thunderstorms this evening are possible. .OUTLOOK FOR 12Z Saturday through Tuesday... .Saturday through Sunday night...VFR. .Monday-Monday night...Mainly VFR, except MVFR or lower possible in scattered late day/evening thunderstorms. .Tuesday...VFR.
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&& .MARINE...
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SCA remains in effect for the ocean waters and the south shore bays of Long Island due to an increasing SW flow today. Gusts up to 30 kt are expected...especially late this aftn and eve as low level winds peak. Seas on the ocean will also build to advsy levels in response to the strong winds. Only change to the headline was to pad the timing a few hours on the south shore bays...which now expires at 11pm. A cold front moves across early Saturday with conditions dropping below SCA levels. High pressure will influence the waters from Saturday night through Monday. A cold front passes through the waters Monday night, and then high pressure returns for the middle of next week. Sub-SCA conditions expected for the period.
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&& .HYDROLOGY...
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Boundary layer winds increase today so any thunderstorms this aftn and tonight will be faster moving, mitigating the flood threat. Still though, some localized minor urban and small stream flooding will be possible. Scattered showers and thunderstorms will impact the region Monday afternoon and Monday night. PWATs will range from 2-2.5 inches, resulting in the potential for locally heavy rain. Localized minor urban and small stream flooding is possible.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Heat Advisory from noon today to 7 PM EDT Saturday for NYZ072>075-176-178. High Rip Current Risk from 10 AM EDT this morning through this evening for NYZ075-080-081-178-179. NJ...Heat Advisory from noon today to 7 PM EDT this evening for NJZ004-006-103>108. MARINE...Small Craft Advisory from noon today to 6 AM EDT Saturday for ANZ350-353-355. Small Craft Advisory from noon today to 11 PM EDT this evening for ANZ345.
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