Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 180528 AFDOKX Area Forecast Discussion National Weather Service New York NY 1228 AM EST Sat Nov 18 2017 .SYNOPSIS... High pressure builds over the region overnight into early Saturday. A warm front will lift to the north later Saturday, then a strong cold front will approach Saturday night, and sweep sweep eastward Sunday morning as strong low pressure passes to the north. A few weather disturbances are possible later next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Winds continue to diminish as high pressure builds over the region under mostly clear to clear conditions. Will be ideal radiational cooling, however, a few knots of wind will make for a trick low temperature forecast. The temperature at KFOK varied from 35 to 26, and back up to 35 in a few hours as wind speeds varied. The NYC metro will remain relatively warm as outlying areas radiate. Minor changes to hourly trends and overnight lows. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... Main concern will be an intensifying low moving into the Ohio Valley Sat morning, then across the lower Great Lakes Sat night and into the St. Lawrence Valley in Sunday. An associated warm front will lift north of the area daytime Sat, with some showers moving into the area from NYC north/west in the afternoon. The pressure gradient between the departing high and the approaching low will quickly tighten up, with S-SW winds gusting to 25-30 mph in most places, and as high as 35 mph across Long Island. Main impacts ahead of and following a strong cold trailing the low expected Sat night into Sunday, with S-SW winds increasing further and a band of moderate to heavy showers sweeping across with the front overnight. Models show fairly good low level mixing with max boundary layer winds from 40-55 kt, highest across eastern Long Island and SE coastal CT. Do not think the full complement of these winds will mix down to the surface, but gusts up to 35 mph are likely inland, 40-45 mph in NYC metro and along most of the coastline, and 50-55 mph across eastern Long Island. Confidence level in seeing winds over 60 mph is not quite high enough to warrant a high wind watch for eastern coastal sections, but this could change with later forecasts. Will have to watch band of moderate to heavy showers with the cold front itself for best low level momentum transfer on the western fringe of the low level jet. Winds could abate somewhat right after cold fropa, then should pick up from mid morning into the afternoon after the passage of a strong mid level vort max, via strong downward momentum transfer of W-NW 40-kt H9 winds to the surface, with gusts up to or just over 45 mph likely during this time frame. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... A broad area of high pressure will build into the region Monday and Tuesday. This will produce fair weather. SuperBlend was used for temperatures except for Monday night, where MEX was used to better capture radiational cooling. Wednesday remains a bit of a question. A cold front will be approaching from the west. In addition, there remains the suggestion that some semblance of a coastal low will develop. The 12Z GFS is way off the Southeast coast and not a factor. The 12Z ECMWF is trending west and now produces a solid swath of rain across the area. The forecast has been trended towards the ECMWF, with low chances for precipitation included for all areas. The rain would help to suppress high temperatures as well. The cooler SuperBlend was used as a result. The cold front comes through Wednesday night. The ECMWF is much different than the GFS, which pours the cold air into the region. The ECMWF keeps the coldest air locked to the north of the area, most likely due to the dynamics of the strengthening offshore low. A blend of the models was used, however depending on how the pattern ultimately develops, Thanksgiving temperatures could end up being roughly plus or minus 5 degrees from the current forecast for highs. All solutions are dry for the day however, followed by a continuation of the dry weather on Friday. The GFS does spin up a low along the subtropical jet and tracks it east of the area on Friday. The ECMWF spins up something similar on Saturday. This feature will need to be watched for any westward trend. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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High pressure slides east of the region today, with a low pressure system approaching from the West. VFR through this morning, with increasing potential for rain showers and MVFR or lower conds developing late today into tonight. Southerly winds increase this morning into this afternoon. SW winds 15 to 20 kt with gusts 25 to 30 kt likely for coastal terminals late today into this evening. .OUTLOOK FOR 06Z SUNDAY THROUGH WEDNESDAY... .Late Saturday Night...MVFR or lower conditions in -SHRA. LLWS possible for eastern terminals at night due to SW flow 40-50 kt at 2 kft AGL. S-SW winds G25-35KT and occasionally higher for coastal terminals. Low prob for a band of +SHRA and isolated thunder. .Sunday...Conditions gradually improve to VFR with showers ending by afternoon. Strong NW windshift Sunday morning, with NW winds G30- 40KT through the day. Gusts diminish to 25-30 kt Sunday evening. .Monday...VFR. W-NW winds G20-30KT. Gusts diminish gradually at night. .Tuesday...Mainly VFR. MVFR possible late Tuesday night with showers. SW winds G15-20KT. .Wednesday...MVFR possible with showers. W-NW winds G15-20KT.
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&& .MARINE... Winds and seas have diminished across the waters east of Moriches Inlet and cancelled the advisory. Winds and seas remain below advisory levels through the overnight with winds and seas increasing Saturday ahead of an approaching cold front. A Storm Watch has been issued for the eastern ocean waters for Sat night into early Sunday morning, for frequent gusts up to 50 kt in S-SW flow ahead of an approaching strong cold front. Gale warnings have been issued elsewhere, beginning Sat afternoon on the western ocean waters, and elsewhere Sat evening, with S-SW winds increasing to 40-45 kt Sat night. W-NW gales should continue after the cold frontal passage into at least Sunday afternoon, and possibly into Sunday night especially on the ocean. SCA conds will follow into Mon, and are still possible mainly on the ocean into Tue. Conditions may improve to below advy criteria on Wed. && .HYDROLOGY... A band of moderate to locally heavy showers with a strong cold frontal passage late Sat night should cause no more than local nuisance impacts. && .TIDES/COASTAL FLOODING... Water levels will approach minor flood thresholds with Sat morning high tide, but are expected to remain just below. Storm surge guidance for Sunday morning high tide may to be on the low side given the strength of southerly winds expected Sat night into Sunday morning ahead of a cold front. But typically, S/SW winds are not conducive to building surge. There is a low probability of a surge of 1-2 ft Sunday morning. If these surge levels develop, minor coastal impacts in a strong SW/W flow would be felt mainly across eastern portions of the Great South Bay into Moriches Bay. Elsewhere any impacts would be brief and localized. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Gale Warning from 6 PM this evening to 6 PM EST Sunday for ANZ330-335-338-340-345. Storm Watch from this evening through Sunday morning for ANZ350-353. Gale Warning from 1 PM this afternoon to 6 PM EST this evening for ANZ350-353. Gale Warning from 1 PM this afternoon to 6 PM EST Sunday for ANZ355.
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&& $$ SYNOPSIS...JMC/Goodman NEAR TERM...Goodman/19 SHORT TERM...Goodman LONG TERM...JMC AVIATION...NV MARINE...JMC/Goodman/19 HYDROLOGY...JMC/Goodman TIDES/COASTAL FLOODING...

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