Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 271608 AFDOKX Area Forecast Discussion National Weather Service New York NY 1208 PM EDT Thu Apr 27 2017 .SYNOPSIS... Weak low pressure passes to the east today, while a dissipating cold front approaches from the Ohio Valley. The front washes out across the area on Friday. A cold front approaches Saturday and pushes south of the area Saturday night. This front then moves back toward the area as a warm front Sunday night into Monday with the associated cold front moving through Monday night into Tuesday morning. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Some gradual improvement continues across the region with fog becoming more patchy and less dense over the waters but still across most of the eastern waters. Temperatures are warming into well into the 60s for most locations except extreme Eastern Long Island and SE Connecticut as clouds lift higher and low levels dry out. Temperatures and dewpoints remain within a few degrees comparing forecast and observed values. The 12Z OKX sounding confirms the low level subsidence inversion and with the southerly flow, is helping to keep low level moisture in place. Some more breaks in the clouds is forecast this afternoon. It will be considerably warmer today, with highs in the lower 60s along the immediate coast, to the lower 70s from NYC north and west with more of a south to southwest flow.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Upper level ridge passes to the east this evening as a short wave trough pivots NE across the Ohio Valley. The latter of which will send a dissipating cold front into the area toward daybreak. Frontal forcing is weak with the mid level short wave the main source of lift as the front moves into the area. There is also weak elevated instability with a small chance of a thunderstorm late tonight into Friday morning. Rainfall amounts will generally be less than a tenth of inch, but isolated higher amounts are possible with any stronger convection. In addition, low-level warm advection and a S/SE flow tonight will likely result in low clouds, drizzle, and fog ahead of the cold front. Conditions clear out from west to east by late Friday morning with temperatures rising into the 70s just inland from the coast, and a warm as the lower 80s north and west of NYC. Winds become SW in the morning with seabreeze development possible in the afternoon. Temperatures will be about 10 degrees above normal. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Bermuda type high pressure will set up over the north central Atlantic Friday night into Saturday. This will set up a favorable flow for warm temperatures, even across coastal areas, as winds shift to the southwest. High temperatures on Saturday will reach the lower to middle 80s away from the coast, lower to middle 70s along the coast, and upper 60s at the immediate coast. This will also mean a noticeable increase in the humidity levels as dew points rise into the upper 50s to lower 60s across the area. Surface cold front approaches the area from the northwest on Saturday, pushing south of the region Saturday night. This will mean temperatures and dew points drop under cold air advection as winds shift to the north after the cold frontal passage. Zonal flow aloft will be replaced by upper level which moves in from the Great Lakes region Saturday night. There may be some showers and isolated thunderstorms with the passage of the cold front, mainly for inland areas as the marine air over the coastal areas keeps the atmosphere more stable here. Inland, higher temperatures and higher dew points will mean the possibility of a shower or thunderstorm before the cold frontal passage, however, weak ascent will limit activity. Much of Saturday night through much of the day Sunday will remain dry as high pressure noses in from southern Canada. The cold front then moves north as a warm front late in the day Sunday into Sunday night, showers are then once again possible, until the warm front moves north of the area Monday, then showers with slight chance of thunderstorms will be possible, until the associated cold front moves through Monday night into early Tuesday morning. Thereafter, conditions should remain dry through mid-week as the associated low pressure heads away from the area. && .AVIATION /16Z THURSDAY THROUGH MONDAY/...
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A weakening cold front approaches from the west today and into tonight. possibly moving to just west of the terminals by 12Z Friday. Variability with ceilings remains through this afternoon, with the NYC metro terminals MVFR, while outside the metro terminals more variable from IFR to MVFR. Areas of MVFR fog remain, mainly at the coastal terminals. A brief period of VFR possible this afternoon at KEWR/KTEB/KHPN/KSWF Return to IFR or lower throughout this evening. There is a low chance for a passing shower and possibly a rumble of thunder late tonight, with the best chance at western terminals, and even there it is less likely than not to occur. Winds S to SSE 10 KT or less this afternoon. Winds become light and variable again this evening. NY Metro Enhanced Aviation Weather Support... Detailed information...including hourly TAF wind component fcsts can be found at: http:/www.weather.gov/zny/n90 KJFK TAF Comments: Amendments due to variability in ceilings and visibility. Conditions still expected to lower back to IFR toward 22Z. KLGA TAF Comments: Amendments due to variability in ceilings and visibility. Conditions still expected to lower back to IFR toward 22Z. KEWR TAF Comments: Amendments due to variability in ceilings and visibility. A brief period of VFR expected 19Z to 22Z. Conditions still expected to lower back to IFR toward 22Z. KTEB TAF Comments: Amendments due to variability in ceilings and visibility. A brief period of VFR expected 19Z to 22Z. Conditions still expected to lower back to IFR toward 22Z. KHPN TAF Comments: Amendments due to variability in ceilings and visibility. A brief period of VFR expected 19Z to 22Z. Conditions still expected to lower back to IFR toward 22Z. KISP TAF Comments: Amendments due to variability in ceilings and visibility. Mainly MVFR conditions until late this afternoon, toward 22Z, when conditions are expected to lower back to IFR. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .Friday morning...IFR or lower probable. Isolated to scattered showers, a rumble of thunder possible. .Friday afternoon-Sunday...Most likely VFR. .Sunday night-Monday...MVFR or lower possible.
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&& .MARINE...
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Dense fog advisory remains in effect until 2PM for the waters surrounding Eastern Long Island including the ocean between Moriches and Montauk, Peconic and Gardiners Bays, as well as Eastern Long Island Sound. For other waters, the fog has become less dense and more patchy. The fog will eventually dissipate before returning again tonight into early Friday. The fog could be dense once again tonight into early Friday. Winds will stay below SCA through Friday but the higher ocean seas will remain through tonight and perhaps into Friday as well. Non-ocean waters stay below SCA. Ocean seas are more marginal for SCA Friday, at near 5 ft, so left end time of 6am Friday for SCA for hazardous seas on the ocean. Waves diminish Friday night, with 5 ft waves lingering over the eastern ocean zone through midnight. Thereafter, seas should remain below 5 ft through Sunday night, though they may touch 5 ft for a few hours late in the day Saturday into Saturday evening as a southerly to southwesterly flow develops ahead of an approaching cold front. Waves then build Monday through early Tuesday morning, from 5 to 8 ft over the western ocean zone, to 8 to 10 ft over the eastern ocean zone, in response to stronger southerly flow out ahead of another approaching cold front. Wind gusts during late Monday into Monday night could reach 25 kt or slightly higher at times. Waves diminish slowly, but should remain above 5 ft through the rest of the long term.
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&& .HYDROLOGY... Rainfall amounts tonight through Friday morning are generally expected to remain below a tenth of an inch. However, there may be isolated brief heavy downpours in any thunderstorms that develop. No significant rainfall expected in the long term. However, there may be isolated brief heavy downpours in any thunderstorms that develop during this time period. && .TIDES/COASTAL FLOODING... Due to high astronomical tides and an easterly swell the next couple of days, water levels may approach minor coastal flood benchmarks, in particular across the south shore back bays of western LI during the evening high tide cycle. Only 1/3 to 3/4 of a foot of surge is needed for minor flooding. && .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Friday for ANZ350-353-355. Dense Fog Advisory until 2 PM EDT this afternoon for ANZ330- 340-350.
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&& $$ SYNOPSIS...JP/DW NEAR TERM...JM/JP SHORT TERM...DW LONG TERM...JP AVIATION...MET MARINE...JM/JP/DW HYDROLOGY...JP/DW TIDES/COASTAL FLOODING...

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