Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241944 AFDOKX Area Forecast Discussion National Weather Service New York NY 344 PM EDT Sat Sep 24 2016 .SYNOPSIS...
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High pressure over southeast Canada builds across the area through Sunday night. The high slides offshore on Monday. A frontal system moves through on Tuesday. High pressure tries to returns for the mid to late week.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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The first real autumn airmass of the season will be with us through the weekend as a deep upper trough tracks SE across eastern Canada and the northeast. At the same time, polar high pressure centered over Ontario builds southeast toward the region. This will result in a northerly flow with clear skies and overnight lows several degrees below normal. Lows will range from the lower 40s well inland and in the Pine Barrens region of LI, to the lower and mid 50s NYC metro. There remains a high risk for rip current development at ocean beaches through this evening.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
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Unseasonably cool conditions are on tap for Sunday and Sunday night as polar high pressure over eastern Canada builds across the region. Northerly winds will continue to allow dry, cool air to filter into the region. Highs on Sunday will struggle to get into the mid and upper 60s, with lows Sunday night ranging from the upper 30s in the coldest locations, to the lower 50s NYC metro.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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Models in good agreement with deep layered ridging sliding east on Monday...allowing a deep closed low to slide over the Great Lakes/Southern Ontario. General agreement in the upper low sitting over this region through midweek...before model divergence in evolution and opening on the low for the late week period. At the surface...high pressure slides east on Monday...while a cold front associated with the stacked Great lakes low approaches the region Monday Night...and crosses the region Tuesday. Some timing differences exist...but overall good agreement in deep layered lift interacting with southern moisture (1 to 2 std PWAT) bringing a soaking rain during the late Monday night to Tuesday Aft period. An isolated tstm is not out of the question with some weak elevated instability and strong lift ahead of the cold front...but prob is quite low. Appears the cold front pushes far enough east late Tue/Tue night for rain to taper off. Forecast uncertainty continues for the mid to late week on evolution of the closed low and how quickly it opens up and move through the east coast. A more progressive scenario would have high pressure in control for mid to late week with mainly dry and seasonable conditions. Meanwhile a less progressive or cutoff scenario would result in potential for additional waves of low pressure to develop along the cold front and affect the region mid to late week. Forecast is currently weighted towards the former scenario based on ensemble means and operational majority...but the latter unsettled solution is climatologically plausible.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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Canadian high pressure builds in through the weekend. VFR with northerly winds through the TAF period. Some variability in wind direction between 350 and 040 true is likely through 00Z. Gusts may cut off after 23Z, especially away from the immediate coast. .Outlook for 18Z Sunday through Thursday... .SUN-MON...VFR. .TUE...MVFR w/areas of IFR in the morning. Becoming VFR from West to East midday. .WED-THU...VFR.
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&& .MARINE...
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Northerly winds will continue across the waters through Sunday night briefly strengthening late tonight into Sunday morning as the pressure gradient tightens with strong high pressure building in from the NW. Gusts may top out around 20 kt. At the same time, long period SE swells from distant tropical cyclone Karl will continue to impact the ocean waters with seas right around 5 ft. The SCA will remain up through the day Sunday. SCA conditions likely Monday Night into Tuesday on ocean waters, and possible all waters, ahead of an approaching frontal system. Sub sca conditions likely return for midweek with a weak pressure gradient and diminishing southerly swells.
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&& .HYDROLOGY...
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A frontal system moves through Tuesday with a general 1/2 to 1 inch of rain likely...with locally higher swaths possible. Hydrologic impacts are expected to be minor.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...High Rip Current Risk until 8 PM EDT this evening for NYZ075- 080-081-178-179. NJ...None. MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ350-353-355.
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&& $$ SYNOPSIS...NV/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...NV AVIATION...JMC MARINE...NV/DW HYDROLOGY...NV/DW

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