Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 170554 AFDOKX Area Forecast Discussion National Weather Service New York NY 154 AM EDT Mon Jul 17 2017 .SYNOPSIS...
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A dissipating cold front approaches to start the week. Weak high pressure then builds in for the mid week period, followed by a cold frontal passage late Thursday. Weak high pressure returns for the first half of the weekend, followed by another frontal system.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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No changes at this time. Convection associated with a weakening cold front remains well NW of the area. High pressure continues to retreat offshore with a a light southerly flow overnight. Some patch fog over eastern Long Island and southeastern CT towards sunrise. Low temperatures are a few degrees above climatological normals.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
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A strong Atlantic high pressure system will act to weaken and slow the forward progression of a potent short wave that will move into the area today through today night. Its attendant surface front will remain to the north and west of the area with the potential for heavier rain primarily closer to the front. Thunderstorm chances will gradually increase through the day as the short wave approaches, mainly to the north and west of the City as ample surface heating gradually destabilizes the air mass. Although flow aloft will be weak, lapse rates aloft are relatively steep and with veering wind profiles may aid in updraft strength and subsequent hail growth. Additionally, a dry subcloud layer may enhance any downdrafts leading to localized strong to severe wind gusts. SPC has placed the areas to the north and west of the city in a marginal risk for severe weather. High temperatures will be close to climatological normals. Coverage of any showers and thunderstorms will gradually decrease overnight, but isolated activity may continue as the upper low and its associated cool temperatures aloft move overhead. Despite increasing cloud cover aloft and occasional shower activity, stratus and patchy fog may once again develop near the coast. The humid air mass will linger, keeping low temperatures a few degrees above normal.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Global models have trended faster with an end of the week cold frontal passage, but there are still timing discrepancies by as much as 12 hours, from as early as Thursday evening, to as late as Friday morning. A filling upper trough/low moves across the area Tuesday along with a dissipated frontal boundary. Height rises behind the system will result in unseasonably warm conditions for the mid week. Global models are in good overall agreement with the westerlies descending southward along the U.S./Canadian border toward the end of the week, with a cold front forecast to move across the area late Thursday into early Friday. This has trended faster as previously discussed. For the most part, scattered convection will be diurnally driven during the afternoon/early evening hours this week, with the highest chances being across the interior. The best chance though for any organized convection will likely not be until the end of the week with the the cold front. Isolated strong/severe is also a possibility Tuesday afternoon along and ahead of the upper trough. Deep-layered W/NW flow sends a fast moving frontal system into the area this weekend. There are timing issues. For the time, just have a low chance of convection. Nearly seasonable temperatures Tuesday will transition to above normal for mid week with a W/SW flow aloft bringing in 85h temps 16-18C. Nearly seasonable readings return Friday into the weekend. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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A weak cold front over the Great Lakes will slowly sag south and move across New England tonight. VFR today with a chance of some ground fog in the Hudson Valley and CT between 09Z and 12z this morning. Convection forecast to remain north and west of the NYC Metro with a chance to reach KSWF VCNTY late this afternoon. Light SSE flow today. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... TUE-THU...Chance marginal visibility in the early morning due to fog. Isolated showers and TSTMs in the late afternoons, mainly over the interior. FRI...VFR.
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&& .MARINE... A relaxed pressure gradient through Tuesday over the waters will keep coastal ocean waters at or below 3 ft, and seas/waves on non-ocean waters at 1 ft or less. A weak southerly flow will continue across the waters for the mid week period with winds generally less than 10 kt and seas 3 ft or less on the ocean and 1 ft or less elsewhere. && .HYDROLOGY... No significant hydrologic impacts are expected through next week. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...None. && $$ SYNOPSIS...MD/DW NEAR TERM...MD/DW SHORT TERM...MD LONG TERM...DW AVIATION...Tongue MARINE...MD/DW HYDROLOGY...MD/DW

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