Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211626 AFDOKX Area Forecast Discussion National Weather Service New York NY 1226 PM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure over the region moves offshore today and tonight. A cold front approaches from the west Tuesday and passes through Tuesday night into Wednesday morning. High pressure then builds in thereafter through the end of the week with a much drier and cooler airmass. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Forecast still mainly on track with just slight adjustments to temperatures and dewpoints to better match observed trends. Weak quasi-zonal flow aloft with main upper level jet stream well northwest of the region. Surface high pressure moves across the region this morning and offshore this afternoon. Expecting a mainly dry day with just a slight chance of showers and thunderstorms for far western Orange County late this afternoon. 850mb temperatures forecast to reach near 15-16 degrees C. Surface temperatures forecast to reach several degrees warmer than yesterday. Mid 80s to near 90 degrees F for much of the region with mostly sunny conditions for most locations. For sky cover, the western edge of a cirrus shield should be east of the forks region and SE CT by 200 PM. Another area of translucent cirrus moving through northern PA would appear to shift through primarily north of the city in the timeframe of the partial solar eclipse, which runs about 120 PM to 400 PM in NYC with a peak at 244 PM. Cirrus may however develop and pass through the city and Long Island during this period as well, especially if any convection pops up to our west. HRRR indicates this convective potential, but may happen too late to be of much significance. Finally, some cumulus development along sea breezes this afternoon may cause some obstruction within about 10 miles of south-facing coasts. Thinking is that any cumulus would be no more that scattered in nature for most spots that see it. Like previous forecast, a look at the HRRRX conveys a slight decrease during maximum obscuration of sun during eclipse, so adjusted temperature a degree downward at 19Z (3PM local time). There is a low risk of rip currents today, becoming moderate late today at Atlantic beaches. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Rest of the forecast shows high pressure moving farther offshore and a cold front gradually approaching from the west. Upper levels convey an upper level trough with its upper level low based in Ontario approaching the region. Continually more warm and humid conditions are expected. Forecast has warmer temperatures Tuesday, getting hot and humid for quite a few locations. Could see heat indices up to 100 degrees in and around NYC. Precip forecast remains near or below 30 percent for showers and thunderstorms. Not much forcing but increasing instability and possible lee trough forming Tuesday could provide focus for convergence. Models are pretty minimal with forecast rainfall amounts overall tonight through Tuesday. Weak trough evident in lower levels late tonight into early Tuesday will lead to pops more in low end chance for showers and thunderstorms and then expecting much of Tuesday to be dry except for interior locations which will have relatively higher chances for showers and thunderstorms. These locations will be closer to lee trough as well. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A cold front approaches the region Tuesday night and pushes across the forecast area on Wednesday. Expect cloud cover to increase and showers and thunderstorms to develop and move across the region through this time frame. By Wednesday evening, skies will begin to clear and a much cooler airmass will be arriving. Canadian high pressure builds into the region Thursday through the weekend, providing dry and sunny conditions. Temperatures will remain below normal as highs only reach the 70s to near 80 each day. The dry and cooler conditions are expected to continue into Monday. && .AVIATION /16Z MONDAY THROUGH FRIDAY/...
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VFR through the TAF period as high pressure remains in control. An isolated shower or tstm possible late day near KSWF, and early evening for KHPN and the NYC metros. Given earlier upstream activity over western NY, which has died down but should refire this afternoon, have enough confidence to mention VCTS at KSWF. Sea breezes are in at KBDR/KGON, and while direction at most other terminals continues to vary between SW and W. A more S-SW sea breeze should set in this afternoon at KJFK/KISP and reach KLGA late, and KEWR/KTEB could be on the edge of a harbor breeze late as well. Gusts 15-18 kt likely. S-SW winds diminish to less than 10 kt this evening. There is also low potential for development of low clouds/fog late tonight with MVFR or lower flight cat, mainly at KJFK/KISP/KGON. ...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: Occasional G20KT possible during the early evening push. Low chance of a shower or tstm after 01Z. Afternoon haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KLGA TAF Comments: Occasional G20KT possible for the late afternoon/early evening push. Low chance of a shower or tstm after 01Z. Afternoon haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KEWR TAF Comments: Low chance of a shower or tstm after 01Z. Afternoon haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Low chance of a shower or tstm after 01Z. Afternoon haze potential forecast is GREEN, which implies slant range visibility 7SM or greater outside of cloud. KHPN TAF Comments: Low chance of a shower or tstm after 00Z. KISP TAF Comments: Occasional G20KT possible late this afternoon. .OUTLOOK FOR 12Z TUESDAY THROUGH FRIDAY... .Tuesday...Mainly VFR. Isolated afternoon shower/tstm possible. SW winds G15-20KT in the afternoon. .Tuesday Night...Better chance for showers/tstms with MVFR or flight cat. .Wednesday...Lingering showers/tstms possible early, then becoming VFR. NW winds G15-20KT. .Wednesday Night-Friday...VFR.
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&& .MARINE... Starting off with quiet conditions on the waters well below SCA thresholds with the high pressure area building in. The high traverses over the waters this morning and moves offshore this afternoon. The increasing return southerly flow will lead to building seas late with ocean seas according to NWPS reaching near 3 ft by the end of today. Winds gusts maximize near 20 kt late today into early this evening. Ocean seas remain mostly 3 ft tonight into early Tuesday with winds slightly subsiding and then these both increase Tuesday afternoon with SCA conditions coming into place by mid to late afternoon on the ocean. The southerly fetch by that timeframe builds the oceans seas up to near 5 ft. Small Craft Conditions continue Tuesday night into Wednesday as winds and seas remain high with the approach and passage of a cold front. For now, a Small Craft advisory is in effect for the ocean waters through Tuesday night. it is likely the SCA will need to be expanded to the non-ocean waters. Also, SCA conditions will likely continue into Wednesday. Conditions fall below SCA levels late Wednesday into Wednesday night. Winds and seas are then forecast to remain, in the absence of any increased swell, below SCA levels through the weekend. && .HYDROLOGY... No widespread hydrologic impacts are forecast through the week. && .TIDES/COASTAL FLOODING... Tides are running high astronomically. For the South Shore Bays, there is the potential for water levels to just reach the minor coastal flooding benchmarks with this evening`s high tide. Thinking is that it`s more likely that all areas fall just short of flooding with at most only a spot or two perhaps touching minor flooding benchmarks. Will therefore not issue a statement at this time. With a stronger onshore flow on Tuesday, there is a better chance for some spots along the South Shore Bays to reach minor flooding. Too soon to issue any products for this, so will allow subsequent shifts to assess trends and issue any statements or advisories as needed. . && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 3 PM Tuesday to 6 AM EDT Wednesday for ANZ350-353-355. && $$ SYNOPSIS...BC/JM NEAR TERM...JC/JM SHORT TERM...JM LONG TERM...BC AVIATION...Goodman/NV MARINE...BC/JM HYDROLOGY...BC/JM TIDES/COASTAL FLOODING...

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