Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221452 AFDOKX Area Forecast Discussion National Weather Service New York NY 1052 AM EDT Sat Jul 22 2017 .SYNOPSIS...
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A weak front will remain nearly stationary just south of the area through tonight, with waves of low pressure riding along it. This frontal boundary will be in the vicinity Sunday as high pressure builds to the north. The high drifts off the northern New England coast Sunday as a wave of low pressure approaches Monday, passing Tuesday. High pressure will follow late Tuesday and Wednesday. Another wave of low pressure follows for Wednesday night into Friday through Thursday. A cold front will approach Friday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Made minor changes this update to reflect the latest trends in observations and guidance. The forecast appears on track. Thunderstorm complex tracking across Ohio will need to be watched, as this moves east/southeastward. Latest high- resolution models continue to support the idea that the core of this should stay to the S/W of the area today. So dry conditions are anticipated through much, if not the entire day. It will continue to be hot, but expect dew points to remain lower than they have been over the past few days. Will maintain the heat advisory for NYC and Urban NE NJ, as heat indices approach 95. Today will likely mark the 4th consecutive day of 90+ degree temperatures for much of the NYC/NJ urban corridor. There is a moderate risk for the development of rip currents at ocean beaches today.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... The upper level shortwave passes tonight, with an associated area of low pressure passing just to the south per model consensus. As mentioned in the near term section of this product, thunderstorms associated with this feature will need to be watched, with best chances impacting the southern or coastal zones tonight. Greatest instability resides to our south, but ample instability along with support aloft could result in a few gusty storms. Heavy downpours are also expected. Upstream shortwave approaches Sunday, with frontal boundary out ahead of it. Meanwhile high pressure builds to our north and east. In general, any shower activity diminishes in coverage and intensity late tonight and through the day Sunday. Plenty of clouds are anticipated, with some sunshine possible Sunday. Nam/WRF hangs onto the ridge longer, and is thus drier Sunday. Temperatures should cool down some tonight and Sunday, as heights lower, and cloud cover lingers. 60s/70s at night, and 80s during the day expected. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
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Exact placement of frontal boundary and low pressure remains in question Sunday night into Monday, but unsettled weather is expected, with shower and thunderstorm chances continuing through Monday, with lowering chances Tuesday as the sharpening trough moves east. This uncertainty in the models and front placement is observed in large temp disparity in the mos this morning for Monday`s highs. At this time, will split the difference between the cooler nam numbers, and warmer GFS MOS. Weak ridging will build to the west later Tuesday into Wednesday as high pressure builds to the west. The upper flow becomes progressive Wednesday as the western Atlantic ridge weakens and drifts east. Yet another shortwave and cold front will affect the area Wednesday night into Friday.
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&& .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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VFR through today, with local sea breezes developing this afternoon. In fact, sea breeze is just south of KJFK and will likely move through around 15Z. A weak cold front will remain nearly stationary just south of the area through tonight. Low pressure will pass just south along this front tonight. Thunderstorm complexes extending from Western Pennsylvania to northern West Virginia will continue to be watched as they move eastward today into tonight. At this time, think TSTMs with gusty winds and local downpours are likely for the NYC metros after 00Z, and also KISP by late evening or midnight. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late tonight...showers/tstms still likely mainly for the NYC metros and Long island terminals, with MVFR or lower conditions and gusty winds possible. .Sunday-Monday night...Episodes of showers/tstms with MVFR or lower conds possible. .Tuesday...An AM shower possible at KGON, otherwise VFR. .Wednesday...VFR.
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&& .MARINE...
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Made minor changes this update to reflect the latest trends in observations and guidance. The forecast appears on track. A weak pressure gradient overall will keep winds and seas/waves below Small Craft Advisory levels of 25 kt and 5 ft through Saturday night. However, there is the potential for thunderstorms Saturday night that could result in larger waves and higher winds, particularly across the ocean. Winds will remain below small craft levels Sunday through Wednesday. However, ocean seas may build to marginal small craft levels Sunday night into Monday as an easterly flow develops and increases Sunday into Monday night. Then seas are expected to subside for Tuesday and Wednesday.
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&& .HYDROLOGY...
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There is a chance for heavy rainfall tonight across coastal locations of NE NJ, NYC and Long Island. However, still believe that the heaviest precipitation from a convective complex will be mainly to the south of the region. Rainfall could very well range from under a tenth of an inch across portions of southern CT, to between a half to one inch across NYC metro. Additional rainfall is possible Sunday night into Tuesday. Significant hydrologic impacts are not expected at this time.
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&& .TIDES/COASTAL FLOODING... With the approach of the new moon (Sun), tides will run high this weekend into early next week. Positive tidal departures of 1/2 to 1 ft will be needed for minor flooding during the night time high tides during this time. Minor flooding is possible starting with the high tide cycle this evening, mainly in the western south shore bays of LI. A bit more widespread minor flooding is possible Sunday night if an e/ne flow develops ahead of an approaching frontal system. The threat for minor flooding could continue into Monday. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...Heat Advisory until 6 PM EDT this evening for NYZ072>075-176- 178. NJ...Heat Advisory until 6 PM EDT this evening for NJZ006-104-106- 108. MARINE...None.
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&& $$ SYNOPSIS...PW NEAR TERM...Maloit/PW SHORT TERM...PW LONG TERM...MET/PW AVIATION...JP/Goodman MARINE...Maloit/Goodman HYDROLOGY...PW TIDES/COASTAL FLOODING...

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