Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210803 AFDOKX Area Forecast Discussion National Weather Service New York NY 403 AM EDT Mon Aug 21 2017 .SYNOPSIS...
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High pressure moves across the region this morning and offshore this afternoon. High pressure moves farther offshore tonight. A cold front approaches from the west Tuesday into Tuesday night. This cold front will move across the region on Wednesday. A much drier and cooler airmass will move into the region for the end of the week.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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High pressure continues to build in, providing the radiational cooling conditions. Early morning temperatures near sunrise a vast range, mid 50s for rural sections to low 70s in parts of NYC.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
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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. The sky cover forecast still contains some uncertainty for the times of the partial solar eclipse, which should run from about 120 PM to 400 PM in NYC and peak at 244 PM. This deals with how much cirrus moves in as forecast models show some convection in PA developing as well as the sea breeze convergence and resulting cu field and how expansive that gets. 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. Rest of the forecast shows high pressure moving farther offshore and a cold front gradually approaching from the west. 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.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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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.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR through the TAF period as high pressure remains in control. Isolated shra possible late evening for NYC/NJ and NW terminals. SW winds will increase this morning into the afternoon, with southerly sea breeze development at coastal terminals. Gusts of 15 to 20 kt likely this afternoon. SW winds diminish to less than 10 kt this evening. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Monday night...VFR. Isolated shower possible. Low chance MVFR or lower stratus/fog at eastern terminals. .Tuesday-Tuesday Night...Isolated aft shra/tsra. Chance of more widespread showers and thunderstorms with MVFR or lower Tuesday Night into early Wed morning. VFR SW winds G15-20KT Tuesday afternoon. .Wednesday...Becoming VFR in the morning with NW gusts 15-20 kt. .Wednesday Night-Friday...VFR. && .MARINE...
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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.
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&& .HYDROLOGY... No widespread hydrologic impacts are forecast through the week. && .TIDES/COASTAL FLOODING...
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Tides are running high astronomically. For South Shore Bays, there is the potential for some water levels to just reach the minor coastal flooding benchmarks for this afternoon and Tuesday afternoon as the onshore flow increases.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 3 PM Tuesday to 6 AM EDT Wednesday for ANZ350-353-355.
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&& $$ SYNOPSIS...BC/JM NEAR TERM...JM SHORT TERM...JM LONG TERM...BC AVIATION...NV MARINE...BC/JM HYDROLOGY...BC/JM TIDES/COASTAL FLOODING...

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