Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221938 AFDOKX Area Forecast Discussion National Weather Service New York NY 338 PM EDT FRI JUL 22 2016 .SYNOPSIS... High pressure builds further offshore today as a weak 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Things remain quiet on the radar so far today. Given the strength of the surface winds and the general synoptic scale of them, I have trimmed back POPs and the intensity of convection across the area for the early part of this afternoon, especially across Long Island. This does not look a favorable environment with the gradient winds we are seeing for convection to pop up. The NAM WRF seems to have the best handle on convection trends for this evening as it shows some activity developing now near the Finger Lakes which is supported by general composite reflectively trends on radar. It looks like any activity won`t work into our area or pop up in the higher terrain of Orange, Putnum and Upper Passaic Counties until later this afternoon with activity then advecting toward The City and coast this evening (maybe after 9 PM). Thus adjusted POPs and weather wording to match this. Activity should weaken as it drops toward the coast into a less favorable environment with more showers than thunderstorms for central and eastern areas of Long Island. The inverted V signature showing up in soundings supports gusty winds as the main threat in and near storms this evening. SPC continues a slight risk for the much of the area mainly from western Long Island on north and west. Otherwise the big concern this afternoon/evening will be Heat in The City and in northeast New Jersey and the Heat Advisory still looks justified given expected heat index values between 95 and 100 this afternoon and early evening. 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. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... 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. not have the confidence to extend NE NJ attm. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... 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. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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A weak cold front approaches tonight and moves through early Saturday. Scattered convection is possible late this afternoon and early evening out ahead of the front associated with a pre-frontal trough. There are multiple limiting factors for a widespread event, thus confidence is not high for thunderstorms at any one location. Generally VFR conditions expected through the TAF period, except in any thunderstorm that develops. Patchy fog and MVFR vsbys are possible, mainly outside NYC metro during the overnight period. Gusty southwest winds with speeds 15 to 20 KT and gusts to around 25 KT will continue, but become less frequent after sunset. Wind speeds will diminish overnight. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/ KJFK TAF Comments: Gusts up to 30 KT possible late this afternoon. Amendments likely for possible thunderstorms late this afternoon into early this evening. KLGA TAF Comments: Gusts up to 30 KT possible. Amendments likely for possible thunderstorms late this afternoon into early this evening. KEWR TAF Comments: Gusts up to 30 KT possible. Amendments likely for possible thunderstorms late this afternoon into early this evening. KTEB TAF Comments: Gusts up to 30 KT possible. Amendments likely for possible thunderstorms late this afternoon into early this evening. KHPN TAF Comments: Amendments likely for possible thunderstorms late this afternoon into early this evening. KISP TAF Comments: Gusts up to 30 KT possible. Amendments likely for possible thunderstorms late this afternoon into early this evening. .OUTLOOK FOR 18Z Saturday through Wednesday... .Saturday afternoon through Sunday night...VFR. W gusts up to 20 KT possible Saturday afternoon. .Monday-Monday night...Mainly VFR, except MVFR or lower possible in scattered late day/evening thunderstorms. .Tuesday and Wednesday...VFR.
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&& .MARINE... 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. && .HYDROLOGY... 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. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Heat Advisory until 7 PM EDT Saturday for NYZ072>075-176-178. High Rip Current Risk until 9 PM EDT this evening for NYZ075- 080-081-178-179. NJ...Heat Advisory until 7 PM EDT Saturday for NJZ006-106-108. Heat Advisory until 7 PM EDT this evening for NJZ004-103>105- 107. MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ350-353- 355. Small Craft Advisory until 11 PM EDT this evening for ANZ345.
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&& $$ SYNOPSIS...24/MPS NEAR TERM...24 SHORT TERM...24 LONG TERM...MPS AVIATION...CB/DW MARINE...24/MPS HYDROLOGY...24/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.