Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 241626 AFDOKX Area Forecast Discussion National Weather Service New York NY 1226 PM EDT Mon Apr 24 2017 .SYNOPSIS... High pressure moves well east of the southern New England coast today as a wave of low pressure moves off the southeastern coast. The low then tracks up along the eastern seaboard through Thursday. A weak front moves through Friday into Friday night, lingering near the region next weekend as high pressure tries to build along the eastern seaboard. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Minor changes made with this update. Have decided to leave in slight chance of showers for the southernmost portion of the CWA this afternoon as there have been brief light showers in association with radar returns trying to push in from the south. Dry air remains below 700 mb this afternoon, so a brief light shower or two should be the extent of anything that falls here. Mostly cloudy to cloudy conditions otherwise for this afternoon along with high temperatures around normal.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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A weak upper ridge remains into Tuesday then weakens while the mid and lower level ridge weakens. The upper low will be slow to track north, while a broad weak surface low track north. Again precipitation will be slow to move north with probabilities becoming likely by Tuesday morning, and categorical by Tuesday afternoon. Precipitation will be light through Tuesday and there may even be a few breaks at times. Again a strong low level inversion will remain through Tuesday. So despite an increasing pressure gradient force mixing of the low level jet winds of 40 to 50 KTS will limited.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Upper closed low gradually weakens as it moves along the middle Atlantic coast Tuesday night. Surface low and mid/upper level low are stacked as well, so the overall trend for this system is to fill as it approaches. The main mechanism for lift Tuesday night is from isentropic lift as warm and moist air lifts over a warm front to the south. This lift will be enhanced by a 40-55 kt low level jet. The strongest portion of the jet is progged to be over Long Island and southern Connecticut, and this is where highest rainfall totals are expected. These winds will stay aloft with inverted low level temperature profiles. Deep moisture feed around the low off the Atlantic will likely lead to precipitable water values around 200 percent of normal. Moderate to locally heavy rain will be possible Tuesday night, especially across Long Island and southern Connecticut. Totals range from around a half inch west to around an inch east for the Tuesday night period. Low level jet and deepest moisture work east Wednesday morning. Middle levels of the atmosphere dry out as the upper low continues to track up the coast. The rain should transition to light rain or possibly some drizzle with low levels remaining saturated through the day. Saturated low levels look to remain in place Wednesday night into Thursday as the stacked low slowly moves to the north and east. Some question as to whether or not there will be any precipitation. Light rain or possibly drizzle may linger across portions of Long Island and southern CT through Wednesday night. A larger upper trough developing over the CONUS should help to push the low off to the north and east on Thursday, bringing an end to any lingering precip. Low clouds may hang on through the day however. A weak front move through Friday into Friday night. Moisture and lift with this front are not impressive, so not expecting anything more than a few showers at this time. This boundary may linger near the region into the weekend as upper level ridging builds along the east coast. Stronger westerlies may remain over or just to our north, so will need to watch any ripples in the flow as some energy could ride along the periphery of the ridge from the trough out west. Will show a dry forecast on Saturday and then slight chance PoPs on Sunday. A warming trend in temperatures is anticipated Wednesday into the weekend. Highs will continue to increase each day, with temperatures running 10 to 15 degrees above normal by the weekend. Coolest locations will be near the coast as afternoon sea breeze circulations develop. && .AVIATION /16Z MONDAY THROUGH FRIDAY/...
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VFR through the first half of this evening as a low-level ridge across the area gradually gives way to low pressure moving slowly up the East Coast. Mid and high level ceilings will gradually lower through the day with the potential for MVFR/IFR conditions in light rain after 06Z. Some rain is possible for the first half of the evening but conditions are forecast to remain VFR. Winds become E/SE at 10 kt or less through this afternoon for most terminals. There will likely be some variability of the flow by 20 to 30 degrees at times. Winds begin to back around to the E/NE this evening. NY Metro Enhanced Aviation Weather Support... Detailed information, including hourly TAF wind component forecasts, can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: Winds may vary +/- 20 to 30 degrees. KLGA TAF Comments: Winds may vary +/- 20 to 30 degrees. KEWR TAF Comments: Winds may vary +/- 20 to 30 degrees. The afternoon KEWR haze potential forecast is GREEN...which implies slant range visibility 7SM or greater outside of cloud. KTEB TAF Comments: Winds may vary +/- 20 to 30 degrees. KHPN TAF Comments: Winds may vary +/- 20 to 30 degrees. KISP TAF Comments: Winds may vary +/- 20 to 30 degrees. .OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY... .Tonight...MVFR/IFR in rain late. .Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast possible during the day. .Wednesday...MVFR/IFR, possibly improving to VFR later in the day. .Thursday-Friday...VFR.
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&& .MARINE... No changes to the forecast at this time as all appears to be on track. High pressure east of Long Island and extending west into the forecast waters will move east through today as a low over the southeastern states moves off the southeastern coast. The low will slowly deepen and track north along the coast tonight into Tuesday. A weak surface pressure gradient force will increase as the low moves north. Sustained easterly winds will increase tonight, reaching to near small craft advisory levels on the ocean waters. Winds will also become gusty, however, with a strong low level inversion developing mixing will be limited. Gusts will be around small craft levels on the ocean late tonight, and then on the remainder of the waters by Tuesday morning, continuing into Tuesday evening. Seas build on the ocean waters and will remain above small craft through at least Tuesday. SCA winds gradually weaken Tuesday night on LI Sound, LI Bays, and the NY Harbor. However, SCA wind gusts are likely to continue on the ocean and seas will continue to build. Winds will remain below gale force as low level inversion prevents stronger winds from mixing down. Winds diminish below SCA on Wednesday on the ocean, and will remain under criteria on all waters until the end of the week. E-SE swells will keep ocean seas elevated through Friday. && .HYDROLOGY... Total rainfall of 3/4 to 2 inches of rainfall is possible tonight into Wednesday. The highest amounts are most likely to occur across eastern Long Island and southeastern Connecticut, where minor flooding of poor drainage and low lying areas is possible. && .TIDES/COASTAL FLOODING... There is the potential for minor coastal flooding along the southern bays of western Long Island and western Long Island Sound with the Tuesday evening high tide cycle. This is in response to a low pressure system moving northward along the eastern seaboard. Only 1/2 to 1 foot of surge is needed to reach minor flood thresholds Tuesday evening. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ330- 335-338-340-345. Small Craft Advisory from 2 AM Tuesday to 6 AM EDT Wednesday for ANZ350-353-355. && $$ SYNOPSIS...DS/MET NEAR TERM...JC/MET SHORT TERM...MET LONG TERM...DS AVIATION...JM/DW MARINE...DS/MET HYDROLOGY...DS TIDES/COASTAL FLOODING...

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