Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211644 AFDOKX Area Forecast Discussion National Weather Service New York NY 1244 PM EDT Mon Jun 21 2021 .SYNOPSIS... A cold front will slowly approach from the west late today into Tuesday, then pass east Tuesday night. High pressure will settle over the Northeast on Wednesday, then shift offshore later this week. The next frontal system will approach from the west near the end of the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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This update accounts for the latest observations and trends in temperatures, dew points, and sky cover. The low stratus deck is slowly making its way east as drier air begins to move in from the SW of the NYC metro. Gradual clearing will be possible across Long Island and SW CT through the early afternoon. Another warm and muggy day is expected as temperatures climb into the middle and upper 80s. Can not rule out a few 90s across metro NJ. Across Long Island and much of coastal CT, temperatures will remain in the lower to mid 80s. With dew points in the upper 60s and potentially lower 70s, heat index values in the afternoon are expected to reach the middle 90s for portions of the Lower Hudson Valley, NYC metro, and NE NJ. A pre-frontal trough approaches from the west with showers and thunderstorms in the late afternoon and evening. Many of the high- res models and CAM`s hold much of the activity off until around or after 23z (7pm). However, there is a possibility that some storms could develop earlier than forecast. Regardless, any strong storms will be capable of producing gusty winds along with heavy rain as PWATs will be 1.5-2.0". Much of the convective activity should weaken fairly quickly as it approaches Long Island and CT as it should be after sunset and it encounters a more stable airmass. The best chance for any severe thunderstorms will be in the Lower Hudson Valley, mainly Orange County. Meanwhile, whatever is left of Claudette will pass well to the southeast this afternoon with little if any impact for the area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... A cold front approaches the region overnight with the chance of showers and isolated thunderstorms continuing through much of the evening and into the overnight. The best chances for any storms will be north and west of NYC early on. After 02-04z (10pm-12am), any shower activity should be scattered at best. The cold front move across the region Tuesday morning with much of the precip generated by it falling in its wake. Though an isolated thunderstorm will be possible, much of the precipitation should be in the form of rain showers during much of the day on Tuesday. Highs will be in the 70s. Behind the cold front, temperatures and dew points fall with lows Tuesday night in the 50s. The biggest change will be dew points in the 40s by daybreak Wednesday morning. Any showers end overnight Tuesday as high pressure builds in from the west. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Just some minor changes in the long term, but stuck close to the NBM guidance. Otherwise, dry conditions expected to start the long term as a +1020 mb high pressure system builds behind an exiting mid- level trough Wednesday and settles into New England through the middle of next week. The area will likely see 1000-500 mb RH values less than 10% overhead with PWAT values falling to less than half an inch. This means rain chances are near zero through Thursday night. Expected afternoon temperatures in the low 80s and upper 70s which are near diurnal averages. Friday could be interesting meteorologically speaking. Global models are beginning to depict a broad low pressure system near North Carolina forming off the decaying front from earlier in the week. This inverted trough rides the synoptic flow north nearing Long Island Friday. With it precipitable water values increase to around 1.5-1.7 inches. Depending on the nature of the system and its proximity, southern New York could see increased rain chances for Friday. Attention shifts over the weekend to the trough and frontal system deepening near the Ohio River valley. This could be a fairly a traditional frontal system with CAPE values around 500-1000 J/kg and unidirectional shear meaning that strong to severe thunderstorms may be possible. The exact timing remains uncertain, but current guidance is hinting towards a Sunday into Monday timeframe. && .AVIATION /16Z MONDAY THROUGH FRIDAY/...
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A weak pre-frontal trough approaches the area tonight. Conditions improving to VFR or MVFR from west to east this afternoon. The exception is KGON where IFR cigs may persist for much of the afternoon. A good chance of thunderstorms exists late the day at KSWF and possibly KHPN, then down into the NYC metros and possibly KBDR this evening between 00 and 04z. Thunderstorms may be severe with gusty winds and hail across the interior (KSWF). MVFR and local IFR cigs should follow for the overnight. Winds S 15-20 kt at KJFK and 10-15 kt elsewhere. Gusts 20-25 kt this afternoon, with the higher gusts in the NYC metro areas. Gusts end and winds diminish this evening. ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... AMD likely for flight cat changes. Higher confidence in winds. .OUTLOOK FOR 18Z TUESDAY THROUGH SATURDAY... .Tuesday...MVFR or lower mainly in the afternoon. Showers likely with chance of tstms. .Wednesday and Thursday...VFR. .Friday and Saturday...Mainly VFR. Detailed information, including hourly TAF wind component forecasts, can be found at: https:/www.weather.gov/zny/n90
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&& .MARINE...
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Sub-SCA conditions are expected this afternoon. Winds out ahead of a cold front will increase on the ocean to 10-15 kt with gusts up to 25 kt this afternoon. Seas will also rise to around 5 ft by this afternoon and linger into tonight as whatever is left of Claudette passes by well to the SE. Have issued SCA on the ocean waters for this timeframe. Seas look to stay elevated Tuesday into Tuesday night as well so SCA may have to be extended. As a high builds into the marine zones, winds relax to 5-10 kt with seas falling to around 3 feet through mid week. As the high shifts over the Atlantic on Friday, winds strengthen slightly out of the southwest increasing to around 15 kt. By the end of the weekend SCA conditions may be possible with the arrival of the next frontal boundary with ocean seas building to more than 5 ft.
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&& .HYDROLOGY... Some downpours are possible late this afternoon into Tuesday, with nuisance flooding a possibility. && .TIDES/COASTAL FLOODING... A moderate rip current risk is forecast at the ocean beaches for today. A high rip current risk is forecast at the ocean beaches on Tuesday. Water levels along the south shore of Nassau county (mainly near the ocean inlets as opposed to the mainland canals/coves) and Jamaica Bay may approach minor thresholds with the upcoming high tide cycle late today. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ353-355. Small Craft Advisory until 8 AM EDT Tuesday for ANZ350.
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&& $$ SYNOPSIS...BC/DJ NEAR TERM...BC/MW SHORT TERM...BC LONG TERM...BC/DJ AVIATION...IRD MARINE...BC/DJ HYDROLOGY...BC/DJ TIDES/COASTAL FLOODING...BG

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